/**
 * @file llrender.cpp
 * @brief LLRender implementation
 *
 * $LicenseInfo:firstyear=2001&license=viewerlgpl$
 * Second Life Viewer Source Code
 * Copyright (C) 2010, Linden Research, Inc.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation;
 * version 2.1 of the License only.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
 * $/LicenseInfo$
 */

#include "linden_common.h"

#include "llrender.h"

#include "llvertexbuffer.h"
#include "llcubemap.h"
#include "llglslshader.h"
#include "llimagegl.h"
#include "llrendertarget.h"
#include "lltexture.h"
#include "llshadermgr.h"
#include "hbxxh.h"

#if LL_WINDOWS
extern void APIENTRY gl_debug_callback(GLenum source,
                                GLenum type,
                                GLuint id,
                                GLenum severity,
                                GLsizei length,
                                const GLchar* message,
                                GLvoid* userParam)
;
#endif

thread_local LLRender gGL;

// Handy copies of last good GL matrices
F32 gGLModelView[16];
F32 gGLLastModelView[16];
F32 gGLLastProjection[16];
F32 gGLProjection[16];

// transform from last frame's camera space to this frame's camera space (and inverse)
F32 gGLDeltaModelView[16];
F32 gGLInverseDeltaModelView[16];

S32 gGLViewport[4];


U32 LLRender::sUICalls = 0;
U32 LLRender::sUIVerts = 0;
U32 LLTexUnit::sWhiteTexture = 0;
bool LLRender::sGLCoreProfile = false;
bool LLRender::sNsightDebugSupport = false;
LLVector2 LLRender::sUIGLScaleFactor = LLVector2(1.f, 1.f);

struct LLVBCache
{
    LLPointer<LLVertexBuffer> vb;
    std::chrono::steady_clock::time_point touched;
};

static std::unordered_map<U64, LLVBCache> sVBCache;

static const GLenum sGLTextureType[] =
{
    GL_TEXTURE_2D,
    GL_TEXTURE_RECTANGLE,
    GL_TEXTURE_CUBE_MAP,
    GL_TEXTURE_CUBE_MAP_ARRAY,
    GL_TEXTURE_2D_MULTISAMPLE,
    GL_TEXTURE_3D
};

static const GLint sGLAddressMode[] =
{
    GL_REPEAT,
    GL_MIRRORED_REPEAT,
    GL_CLAMP_TO_EDGE
};

const U32 immediate_mask = LLVertexBuffer::MAP_VERTEX | LLVertexBuffer::MAP_COLOR | LLVertexBuffer::MAP_TEXCOORD0;

static const GLenum sGLBlendFactor[] =
{
    GL_ONE,
    GL_ZERO,
    GL_DST_COLOR,
    GL_SRC_COLOR,
    GL_ONE_MINUS_DST_COLOR,
    GL_ONE_MINUS_SRC_COLOR,
    GL_DST_ALPHA,
    GL_SRC_ALPHA,
    GL_ONE_MINUS_DST_ALPHA,
    GL_ONE_MINUS_SRC_ALPHA,

    GL_ZERO // 'BF_UNDEF'
};

LLTexUnit::LLTexUnit(S32 index)
    : mCurrTexType(TT_NONE),
    mCurrColorScale(1), mCurrAlphaScale(1), mCurrTexture(0),
    mHasMipMaps(false),
    mIndex(index)
{
    llassert_always(index < (S32)LL_NUM_TEXTURE_LAYERS);
}

//static
U32 LLTexUnit::getInternalType(eTextureType type)
{
    return sGLTextureType[type];
}

void LLTexUnit::refreshState(void)
{
    // We set dirty to true so that the tex unit knows to ignore caching
    // and we reset the cached tex unit state

    gGL.flush();

    glActiveTexture(GL_TEXTURE0 + mIndex);

    if (mCurrTexType != TT_NONE)
    {
        glBindTexture(sGLTextureType[mCurrTexType], mCurrTexture);
    }
    else
    {
        glBindTexture(GL_TEXTURE_2D, 0);
    }
}

void LLTexUnit::activate(void)
{
    if (mIndex < 0) return;

    if ((S32)gGL.mCurrTextureUnitIndex != mIndex || gGL.mDirty)
    {
        gGL.flush();
        glActiveTexture(GL_TEXTURE0 + mIndex);
        gGL.mCurrTextureUnitIndex = mIndex;
    }
}

void LLTexUnit::enable(eTextureType type)
{
    if (mIndex < 0) return;

    if ( (mCurrTexType != type || gGL.mDirty) && (type != TT_NONE) )
    {
        activate();
        if (mCurrTexType != TT_NONE && !gGL.mDirty)
        {
            disable(); // Force a disable of a previous texture type if it's enabled.
        }
        mCurrTexType = type;

        gGL.flush();
    }
}

void LLTexUnit::disable(void)
{
    if (mIndex < 0) return;

    if (mCurrTexType != TT_NONE)
    {
        unbind(mCurrTexType);
        mCurrTexType = TT_NONE;
    }
}

void LLTexUnit::bindFast(LLTexture* texture)
{
    LLImageGL* gl_tex = texture->getGLTexture();
    texture->setActive();
    glActiveTexture(GL_TEXTURE0 + mIndex);
    gGL.mCurrTextureUnitIndex = mIndex;
    mCurrTexture = gl_tex->getTexName();
    if (!mCurrTexture)
    {
        LL_PROFILE_ZONE_NAMED("MISSING TEXTURE");
        //if deleted, will re-generate it immediately
        texture->forceImmediateUpdate();
        gl_tex->forceUpdateBindStats();
        texture->bindDefaultImage(mIndex);
    }
    glBindTexture(sGLTextureType[gl_tex->getTarget()], mCurrTexture);
    mHasMipMaps = gl_tex->mHasMipMaps;
}

bool LLTexUnit::bind(LLTexture* texture, bool for_rendering, bool forceBind)
{
    LL_PROFILE_ZONE_SCOPED_CATEGORY_PIPELINE;
    stop_glerror();
    if (mIndex >= 0)
    {
        gGL.flush();

        LLImageGL* gl_tex = NULL ;

        if (texture != NULL && (gl_tex = texture->getGLTexture()))
        {
            if (gl_tex->getTexName()) //if texture exists
            {
                //in audit, replace the selected texture by the default one.
                if ((mCurrTexture != gl_tex->getTexName()) || forceBind)
                {
                    activate();
                    enable(gl_tex->getTarget());
                    mCurrTexture = gl_tex->getTexName();
                    glBindTexture(sGLTextureType[gl_tex->getTarget()], mCurrTexture);
                    if(gl_tex->updateBindStats())
                    {
                        texture->setActive() ;
                        texture->updateBindStatsForTester() ;
                    }
                    mHasMipMaps = gl_tex->mHasMipMaps;
                    if (gl_tex->mTexOptionsDirty)
                    {
                        gl_tex->mTexOptionsDirty = false;
                        setTextureAddressMode(gl_tex->mAddressMode);
                        setTextureFilteringOption(gl_tex->mFilterOption);
                    }
                }
            }
            else
            {
                //if deleted, will re-generate it immediately
                texture->forceImmediateUpdate() ;

                gl_tex->forceUpdateBindStats() ;
                return texture->bindDefaultImage(mIndex);
            }
        }
        else
        {
            if (texture)
            {
                LL_DEBUGS() << "NULL LLTexUnit::bind GL image" << LL_ENDL;
            }
            else
            {
                LL_DEBUGS() << "NULL LLTexUnit::bind texture" << LL_ENDL;
            }
            return false;
        }
    }
    else
    { // mIndex < 0
        return false;
    }

    return true;
}

bool LLTexUnit::bind(LLImageGL* texture, bool for_rendering, bool forceBind, S32 usename)
{
    stop_glerror();
    if (mIndex < 0) return false;

    U32 texname = usename ? usename : texture->getTexName();

    if(!texture)
    {
        LL_DEBUGS() << "NULL LLTexUnit::bind texture" << LL_ENDL;
        return false;
    }

    if(!texname)
    {
        if(LLImageGL::sDefaultGLTexture && LLImageGL::sDefaultGLTexture->getTexName())
        {
            return bind(LLImageGL::sDefaultGLTexture) ;
        }
        stop_glerror();
        return false ;
    }

    if ((mCurrTexture != texname) || forceBind)
    {
        gGL.flush();
        stop_glerror();
        activate();
        stop_glerror();
        enable(texture->getTarget());
        stop_glerror();
        mCurrTexture = texname;
        glBindTexture(sGLTextureType[texture->getTarget()], mCurrTexture);
        stop_glerror();
        texture->updateBindStats();
        mHasMipMaps = texture->mHasMipMaps;
        if (texture->mTexOptionsDirty)
        {
            stop_glerror();
            texture->mTexOptionsDirty = false;
            setTextureAddressMode(texture->mAddressMode);
            setTextureFilteringOption(texture->mFilterOption);
            stop_glerror();
        }
    }

    stop_glerror();

    return true;
}

bool LLTexUnit::bind(LLCubeMap* cubeMap)
{
    if (mIndex < 0) return false;

    gGL.flush();

    if (cubeMap == NULL)
    {
        LL_WARNS() << "NULL LLTexUnit::bind cubemap" << LL_ENDL;
        return false;
    }

    if (mCurrTexture != cubeMap->mImages[0]->getTexName())
    {
        if (LLCubeMap::sUseCubeMaps)
        {
            activate();
            enable(LLTexUnit::TT_CUBE_MAP);
            mCurrTexture = cubeMap->mImages[0]->getTexName();
            glBindTexture(GL_TEXTURE_CUBE_MAP, mCurrTexture);
            mHasMipMaps = cubeMap->mImages[0]->mHasMipMaps;
            cubeMap->mImages[0]->updateBindStats();
            if (cubeMap->mImages[0]->mTexOptionsDirty)
            {
                cubeMap->mImages[0]->mTexOptionsDirty = false;
                setTextureAddressMode(cubeMap->mImages[0]->mAddressMode);
                setTextureFilteringOption(cubeMap->mImages[0]->mFilterOption);
            }
            return true;
        }
        else
        {
            LL_WARNS() << "Using cube map without extension!" << LL_ENDL;
            return false;
        }
    }
    return true;
}

// LLRenderTarget is unavailible on the mapserver since it uses FBOs.
bool LLTexUnit::bind(LLRenderTarget* renderTarget, bool bindDepth)
{
    if (mIndex < 0) return false;

    gGL.flush();

    if (bindDepth)
    {
        llassert(renderTarget->getDepth()); // target MUST have a depth buffer attachment

        bindManual(renderTarget->getUsage(), renderTarget->getDepth());
    }
    else
    {
        bindManual(renderTarget->getUsage(), renderTarget->getTexture());
    }

    return true;
}

bool LLTexUnit::bindManual(eTextureType type, U32 texture, bool hasMips)
{
    if (mIndex < 0)
    {
        return false;
    }

    if(mCurrTexture != texture)
    {
        gGL.flush();

        activate();
        enable(type);
        mCurrTexture = texture;
        glBindTexture(sGLTextureType[type], texture);
        mHasMipMaps = hasMips;
    }
    return true;
}

void LLTexUnit::unbind(eTextureType type)
{
    stop_glerror();

    if (mIndex < 0) return;

    //always flush and activate for consistency
    //   some code paths assume unbind always flushes and sets the active texture
    gGL.flush();
    activate();

    // Disabled caching of binding state.
    if (mCurrTexType == type)
    {
        mCurrTexture = 0;

        if (type == LLTexUnit::TT_TEXTURE)
        {
            glBindTexture(sGLTextureType[type], sWhiteTexture);
        }
        else
        {
            glBindTexture(sGLTextureType[type], 0);
        }
        stop_glerror();
    }
}

void LLTexUnit::unbindFast(eTextureType type)
{
    activate();

    // Disabled caching of binding state.
    if (mCurrTexType == type)
    {
        mCurrTexture = 0;

        if (type == LLTexUnit::TT_TEXTURE)
        {
            glBindTexture(sGLTextureType[type], sWhiteTexture);
        }
        else
        {
            glBindTexture(sGLTextureType[type], 0);
        }
    }
}

void LLTexUnit::setTextureAddressMode(eTextureAddressMode mode)
{
    if (mIndex < 0 || mCurrTexture == 0) return;

    gGL.flush();

    activate();

    glTexParameteri (sGLTextureType[mCurrTexType], GL_TEXTURE_WRAP_S, sGLAddressMode[mode]);
    glTexParameteri (sGLTextureType[mCurrTexType], GL_TEXTURE_WRAP_T, sGLAddressMode[mode]);
    if (mCurrTexType == TT_CUBE_MAP)
    {
        glTexParameteri (GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_R, sGLAddressMode[mode]);
    }
}

void LLTexUnit::setTextureFilteringOption(LLTexUnit::eTextureFilterOptions option)
{
    if (mIndex < 0 || mCurrTexture == 0 || mCurrTexType == LLTexUnit::TT_MULTISAMPLE_TEXTURE) return;

    gGL.flush();

    if (option == TFO_POINT)
    {
        glTexParameteri(sGLTextureType[mCurrTexType], GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    }
    else
    {
        glTexParameteri(sGLTextureType[mCurrTexType], GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    }

    if (option >= TFO_TRILINEAR && mHasMipMaps)
    {
        glTexParameteri(sGLTextureType[mCurrTexType], GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
    }
    else if (option >= TFO_BILINEAR)
    {
        if (mHasMipMaps)
        {
            glTexParameteri(sGLTextureType[mCurrTexType], GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_NEAREST);
        }
        else
        {
            glTexParameteri(sGLTextureType[mCurrTexType], GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        }
    }
    else
    {
        if (mHasMipMaps)
        {
            glTexParameteri(sGLTextureType[mCurrTexType], GL_TEXTURE_MIN_FILTER, GL_NEAREST_MIPMAP_NEAREST);
        }
        else
        {
            glTexParameteri(sGLTextureType[mCurrTexType], GL_TEXTURE_MIN_FILTER, GL_NEAREST);
        }
    }

    if (gGLManager.mGLVersion >= 4.59f)
    {
        if (LLImageGL::sGlobalUseAnisotropic && option == TFO_ANISOTROPIC)
        {
            glTexParameterf(sGLTextureType[mCurrTexType], GL_TEXTURE_MAX_ANISOTROPY, gGLManager.mMaxAnisotropy);
        }
        else
        {
            glTexParameterf(sGLTextureType[mCurrTexType], GL_TEXTURE_MAX_ANISOTROPY, 1.f);
        }
    }
}

GLint LLTexUnit::getTextureSource(eTextureBlendSrc src)
{
    switch(src)
    {
        // All four cases should return the same value.
        case TBS_PREV_COLOR:
        case TBS_PREV_ALPHA:
        case TBS_ONE_MINUS_PREV_COLOR:
        case TBS_ONE_MINUS_PREV_ALPHA:
            return GL_PREVIOUS;

        // All four cases should return the same value.
        case TBS_TEX_COLOR:
        case TBS_TEX_ALPHA:
        case TBS_ONE_MINUS_TEX_COLOR:
        case TBS_ONE_MINUS_TEX_ALPHA:
            return GL_TEXTURE;

        // All four cases should return the same value.
        case TBS_VERT_COLOR:
        case TBS_VERT_ALPHA:
        case TBS_ONE_MINUS_VERT_COLOR:
        case TBS_ONE_MINUS_VERT_ALPHA:
            return GL_PRIMARY_COLOR;

        // All four cases should return the same value.
        case TBS_CONST_COLOR:
        case TBS_CONST_ALPHA:
        case TBS_ONE_MINUS_CONST_COLOR:
        case TBS_ONE_MINUS_CONST_ALPHA:
            return GL_CONSTANT;

        default:
            LL_WARNS() << "Unknown eTextureBlendSrc: " << src << ".  Using Vertex Color instead." << LL_ENDL;
            return GL_PRIMARY_COLOR;
    }
}

GLint LLTexUnit::getTextureSourceType(eTextureBlendSrc src, bool isAlpha)
{
    switch(src)
    {
        // All four cases should return the same value.
        case TBS_PREV_COLOR:
        case TBS_TEX_COLOR:
        case TBS_VERT_COLOR:
        case TBS_CONST_COLOR:
            return (isAlpha) ? GL_SRC_ALPHA: GL_SRC_COLOR;

        // All four cases should return the same value.
        case TBS_PREV_ALPHA:
        case TBS_TEX_ALPHA:
        case TBS_VERT_ALPHA:
        case TBS_CONST_ALPHA:
            return GL_SRC_ALPHA;

        // All four cases should return the same value.
        case TBS_ONE_MINUS_PREV_COLOR:
        case TBS_ONE_MINUS_TEX_COLOR:
        case TBS_ONE_MINUS_VERT_COLOR:
        case TBS_ONE_MINUS_CONST_COLOR:
            return (isAlpha) ? GL_ONE_MINUS_SRC_ALPHA : GL_ONE_MINUS_SRC_COLOR;

        // All four cases should return the same value.
        case TBS_ONE_MINUS_PREV_ALPHA:
        case TBS_ONE_MINUS_TEX_ALPHA:
        case TBS_ONE_MINUS_VERT_ALPHA:
        case TBS_ONE_MINUS_CONST_ALPHA:
            return GL_ONE_MINUS_SRC_ALPHA;

        default:
            LL_WARNS() << "Unknown eTextureBlendSrc: " << src << ".  Using Source Color or Alpha instead." << LL_ENDL;
            return (isAlpha) ? GL_SRC_ALPHA: GL_SRC_COLOR;
    }
}

void LLTexUnit::setColorScale(S32 scale)
{
    if (mCurrColorScale != scale || gGL.mDirty)
    {
        mCurrColorScale = scale;
        gGL.flush();
        glTexEnvi( GL_TEXTURE_ENV, GL_RGB_SCALE, scale );
    }
}

void LLTexUnit::setAlphaScale(S32 scale)
{
    if (mCurrAlphaScale != scale || gGL.mDirty)
    {
        mCurrAlphaScale = scale;
        gGL.flush();
        glTexEnvi( GL_TEXTURE_ENV, GL_ALPHA_SCALE, scale );
    }
}

// Useful for debugging that you've manually assigned a texture operation to the correct
// texture unit based on the currently set active texture in opengl.
void LLTexUnit::debugTextureUnit(void)
{
    if (mIndex < 0) return;

    GLint activeTexture;
    glGetIntegerv(GL_ACTIVE_TEXTURE, &activeTexture);
    if ((GL_TEXTURE0 + mIndex) != activeTexture)
    {
        U32 set_unit = (activeTexture - GL_TEXTURE0);
        LL_WARNS() << "Incorrect Texture Unit!  Expected: " << set_unit << " Actual: " << mIndex << LL_ENDL;
    }
}

LLLightState::LLLightState(S32 index)
: mIndex(index),
  mEnabled(false),
  mConstantAtten(1.f),
  mLinearAtten(0.f),
  mQuadraticAtten(0.f),
  mSpotExponent(0.f),
  mSpotCutoff(180.f)
{
    if (mIndex == 0)
    {
        mDiffuse.set(1,1,1,1);
        mDiffuseB.set(0,0,0,0);
        mSpecular.set(1,1,1,1);
    }

    mSunIsPrimary = true;

    mAmbient.set(0,0,0,1);
    mPosition.set(0,0,1,0);
    mSpotDirection.set(0,0,-1);
}

void LLLightState::enable()
{
    mEnabled = true;
}

void LLLightState::disable()
{
    mEnabled = false;
}

void LLLightState::setDiffuse(const LLColor4& diffuse)
{
    if (mDiffuse != diffuse)
    {
        ++gGL.mLightHash;
        mDiffuse = diffuse;
    }
}

void LLLightState::setDiffuseB(const LLColor4& diffuse)
{
    if (mDiffuseB != diffuse)
    {
        ++gGL.mLightHash;
        mDiffuseB = diffuse;
    }
}

void LLLightState::setSunPrimary(bool v)
{
    if (mSunIsPrimary != v)
    {
        ++gGL.mLightHash;
        mSunIsPrimary = v;
    }
}

void LLLightState::setSize(F32 v)
{
    if (mSize != v)
    {
        ++gGL.mLightHash;
        mSize = v;
    }
}

void LLLightState::setFalloff(F32 v)
{
    if (mFalloff != v)
    {
        ++gGL.mLightHash;
        mFalloff = v;
    }
}

void LLLightState::setAmbient(const LLColor4& ambient)
{
    if (mAmbient != ambient)
    {
        ++gGL.mLightHash;
        mAmbient = ambient;
    }
}

void LLLightState::setSpecular(const LLColor4& specular)
{
    if (mSpecular != specular)
    {
        ++gGL.mLightHash;
        mSpecular = specular;
    }
}

void LLLightState::setPosition(const LLVector4& position)
{
    //always set position because modelview matrix may have changed
    ++gGL.mLightHash;
    mPosition = position;
    //transform position by current modelview matrix
    glh::vec4f pos(position.mV);
    const glh::matrix4f& mat = gGL.getModelviewMatrix();
    mat.mult_matrix_vec(pos);
    mPosition.set(pos.v);
}

void LLLightState::setConstantAttenuation(const F32& atten)
{
    if (mConstantAtten != atten)
    {
        mConstantAtten = atten;
        ++gGL.mLightHash;
    }
}

void LLLightState::setLinearAttenuation(const F32& atten)
{
    if (mLinearAtten != atten)
    {
        ++gGL.mLightHash;
        mLinearAtten = atten;
    }
}

void LLLightState::setQuadraticAttenuation(const F32& atten)
{
    if (mQuadraticAtten != atten)
    {
        ++gGL.mLightHash;
        mQuadraticAtten = atten;
    }
}

void LLLightState::setSpotExponent(const F32& exponent)
{
    if (mSpotExponent != exponent)
    {
        ++gGL.mLightHash;
        mSpotExponent = exponent;
    }
}

void LLLightState::setSpotCutoff(const F32& cutoff)
{
    if (mSpotCutoff != cutoff)
    {
        ++gGL.mLightHash;
        mSpotCutoff = cutoff;
    }
}

void LLLightState::setSpotDirection(const LLVector3& direction)
{
    //always set direction because modelview matrix may have changed
    ++gGL.mLightHash;
    mSpotDirection = direction;
    //transform direction by current modelview matrix
    glh::vec3f dir(direction.mV);
    const glh::matrix4f& mat = gGL.getModelviewMatrix();
    mat.mult_matrix_dir(dir);

    mSpotDirection.set(dir.v);
}

LLRender::LLRender()
  : mDirty(false),
    mCount(0),
    mQuadCycle(0),
    mMode(LLRender::TRIANGLES),
    mCurrTextureUnitIndex(0)
{
    for (U32 i = 0; i < LL_NUM_TEXTURE_LAYERS; i++)
    {
        mTexUnits[i].mIndex = i;
    }

    for (U32 i = 0; i < LL_NUM_LIGHT_UNITS; ++i)
    {
        mLightState[i].mIndex = i;
    }

    for (U32 i = 0; i < 4; i++)
    {
        mCurrColorMask[i] = true;
    }

    mCurrBlendColorSFactor = BF_UNDEF;
    mCurrBlendAlphaSFactor = BF_UNDEF;
    mCurrBlendColorDFactor = BF_UNDEF;
    mCurrBlendAlphaDFactor = BF_UNDEF;

    mMatrixMode = LLRender::MM_MODELVIEW;

    for (U32 i = 0; i < NUM_MATRIX_MODES; ++i)
    {
        mMatIdx[i] = 0;
        mMatHash[i] = 0;
        mCurMatHash[i] = 0xFFFFFFFF;
    }

    mLightHash = 0;
}

LLRender::~LLRender()
{
    shutdown();
}

bool LLRender::init(bool needs_vertex_buffer)
{
#if LL_WINDOWS
    if (gGLManager.mHasDebugOutput && gDebugGL)
    { //setup debug output callback
        //glDebugMessageControl(GL_DONT_CARE, GL_DONT_CARE, GL_DEBUG_SEVERITY_LOW_ARB, 0, NULL, GL_TRUE);
        glDebugMessageCallback((GLDEBUGPROC) gl_debug_callback, NULL);
        glEnable(GL_DEBUG_OUTPUT_SYNCHRONOUS);
    }
#endif

    glPixelStorei(GL_PACK_ALIGNMENT, 1);
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

    gGL.setSceneBlendType(LLRender::BT_ALPHA);
    gGL.setAmbientLightColor(LLColor4::black);

    glCullFace(GL_BACK);

    // necessary for reflection maps
    glEnable(GL_TEXTURE_CUBE_MAP_SEAMLESS);

#if LL_WINDOWS
    if (glGenVertexArrays == nullptr)
    {
        return false;
    }
#endif

    { //bind a dummy vertex array object so we're core profile compliant
        U32 ret;
        glGenVertexArrays(1, &ret);
        glBindVertexArray(ret);
    }

    if (needs_vertex_buffer)
    {
        initVertexBuffer();
    }
    return true;
}

void LLRender::initVertexBuffer()
{
    llassert_always(mBuffer.isNull());
    stop_glerror();
    mBuffer = new LLVertexBuffer(immediate_mask);
    mBuffer->allocateBuffer(4096, 0);
    mBuffer->getVertexStrider(mVerticesp);
    mBuffer->getTexCoord0Strider(mTexcoordsp);
    mBuffer->getColorStrider(mColorsp);
    stop_glerror();
}

void LLRender::resetVertexBuffer()
{
    mBuffer = NULL;
}

void LLRender::shutdown()
{
    resetVertexBuffer();
}

void LLRender::refreshState(void)
{
    mDirty = true;

    U32 active_unit = mCurrTextureUnitIndex;

    for (U32 i = 0; i < mTexUnits.size(); i++)
    {
        mTexUnits[i].refreshState();
    }

    mTexUnits[active_unit].activate();

    setColorMask(mCurrColorMask[0], mCurrColorMask[1], mCurrColorMask[2], mCurrColorMask[3]);

    flush();

    mDirty = false;
}

void LLRender::syncLightState()
{
    LLGLSLShader *shader = LLGLSLShader::sCurBoundShaderPtr;

    if (!shader)
    {
        return;
    }

    if (shader->mLightHash != mLightHash)
    {
        shader->mLightHash = mLightHash;

        LLVector4 position[LL_NUM_LIGHT_UNITS];
        LLVector3 direction[LL_NUM_LIGHT_UNITS];
        LLVector4 attenuation[LL_NUM_LIGHT_UNITS];
        LLVector3 diffuse[LL_NUM_LIGHT_UNITS];
        LLVector3 diffuse_b[LL_NUM_LIGHT_UNITS];
        bool      sun_primary[LL_NUM_LIGHT_UNITS];
        LLVector2 size[LL_NUM_LIGHT_UNITS];

        for (U32 i = 0; i < LL_NUM_LIGHT_UNITS; i++)
        {
            LLLightState *light = &mLightState[i];

            position[i]  = light->mPosition;
            direction[i] = light->mSpotDirection;
            attenuation[i].set(light->mLinearAtten, light->mQuadraticAtten, light->mSpecular.mV[2], light->mSpecular.mV[3]);
            diffuse[i].set(light->mDiffuse.mV);
            diffuse_b[i].set(light->mDiffuseB.mV);
            sun_primary[i] = light->mSunIsPrimary;
            size[i].set(light->mSize, light->mFalloff);
        }

        shader->uniform4fv(LLShaderMgr::LIGHT_POSITION, LL_NUM_LIGHT_UNITS, position[0].mV);
        shader->uniform3fv(LLShaderMgr::LIGHT_DIRECTION, LL_NUM_LIGHT_UNITS, direction[0].mV);
        shader->uniform4fv(LLShaderMgr::LIGHT_ATTENUATION, LL_NUM_LIGHT_UNITS, attenuation[0].mV);
        shader->uniform2fv(LLShaderMgr::LIGHT_DEFERRED_ATTENUATION, LL_NUM_LIGHT_UNITS, size[0].mV);
        shader->uniform3fv(LLShaderMgr::LIGHT_DIFFUSE, LL_NUM_LIGHT_UNITS, diffuse[0].mV);
        shader->uniform3fv(LLShaderMgr::LIGHT_AMBIENT, 1, mAmbientLightColor.mV);
        shader->uniform1i(LLShaderMgr::SUN_UP_FACTOR, sun_primary[0] ? 1 : 0);
        //shader->uniform3fv(LLShaderMgr::AMBIENT, 1, mAmbientLightColor.mV);
        //shader->uniform3fv(LLShaderMgr::SUNLIGHT_COLOR, 1, diffuse[0].mV);
        //shader->uniform3fv(LLShaderMgr::MOONLIGHT_COLOR, 1, diffuse_b[0].mV);
    }
}

void LLRender::syncMatrices()
{
    STOP_GLERROR;
    LL_PROFILE_ZONE_SCOPED_CATEGORY_DISPLAY;

    static const U32 name[] =
    {
        LLShaderMgr::MODELVIEW_MATRIX,
        LLShaderMgr::PROJECTION_MATRIX,
        LLShaderMgr::TEXTURE_MATRIX0,
        LLShaderMgr::TEXTURE_MATRIX1,
        LLShaderMgr::TEXTURE_MATRIX2,
        LLShaderMgr::TEXTURE_MATRIX3,
    };

    LLGLSLShader* shader = LLGLSLShader::sCurBoundShaderPtr;

    static glh::matrix4f cached_mvp;
    static glh::matrix4f cached_inv_mdv;
    static U32 cached_mvp_mdv_hash = 0xFFFFFFFF;
    static U32 cached_mvp_proj_hash = 0xFFFFFFFF;

    static glh::matrix4f cached_normal;
    static U32 cached_normal_hash = 0xFFFFFFFF;

    if (shader)
    {
        bool mvp_done = false;

        U32 i = MM_MODELVIEW;
        if (mMatHash[MM_MODELVIEW] != shader->mMatHash[MM_MODELVIEW])
        { //update modelview, normal, and MVP
            glh::matrix4f& mat = mMatrix[MM_MODELVIEW][mMatIdx[MM_MODELVIEW]];

            // if MDV has changed, update the cached inverse as well
            if (cached_mvp_mdv_hash != mMatHash[MM_MODELVIEW])
            {
                cached_inv_mdv = mat.inverse();
            }

            shader->uniformMatrix4fv(name[MM_MODELVIEW], 1, GL_FALSE, mat.m);
            shader->mMatHash[MM_MODELVIEW] = mMatHash[MM_MODELVIEW];

            //update normal matrix
            S32 loc = shader->getUniformLocation(LLShaderMgr::NORMAL_MATRIX);
            if (loc > -1)
            {
                if (cached_normal_hash != mMatHash[i])
                {
                    cached_normal = cached_inv_mdv.transpose();
                    cached_normal_hash = mMatHash[i];
                }

                glh::matrix4f& norm = cached_normal;

                F32 norm_mat[] =
                {
                    norm.m[0], norm.m[1], norm.m[2],
                    norm.m[4], norm.m[5], norm.m[6],
                    norm.m[8], norm.m[9], norm.m[10]
                };

                shader->uniformMatrix3fv(LLShaderMgr::NORMAL_MATRIX, 1, GL_FALSE, norm_mat);
            }

            if (shader->getUniformLocation(LLShaderMgr::INVERSE_MODELVIEW_MATRIX))
            {
                shader->uniformMatrix4fv(LLShaderMgr::INVERSE_MODELVIEW_MATRIX, 1, GL_FALSE, cached_inv_mdv.m);
            }

            //update MVP matrix
            mvp_done = true;
            loc = shader->getUniformLocation(LLShaderMgr::MODELVIEW_PROJECTION_MATRIX);
            if (loc > -1)
            {
                U32 proj = MM_PROJECTION;

                if (cached_mvp_mdv_hash != mMatHash[i] || cached_mvp_proj_hash != mMatHash[MM_PROJECTION])
                {
                    cached_mvp = mat;
                    cached_mvp.mult_left(mMatrix[proj][mMatIdx[proj]]);
                    cached_mvp_mdv_hash = mMatHash[i];
                    cached_mvp_proj_hash = mMatHash[MM_PROJECTION];
                }

                shader->uniformMatrix4fv(LLShaderMgr::MODELVIEW_PROJECTION_MATRIX, 1, GL_FALSE, cached_mvp.m);
            }
        }

        i = MM_PROJECTION;
        if (mMatHash[MM_PROJECTION] != shader->mMatHash[MM_PROJECTION])
        { //update projection matrix, normal, and MVP
            glh::matrix4f& mat = mMatrix[MM_PROJECTION][mMatIdx[MM_PROJECTION]];

            // GZ: This was previously disabled seemingly due to a bug involving the deferred renderer's regular pushing and popping of mats.
            // We're reenabling this and cleaning up the code around that - that would've been the appropriate course initially.
            // Anything beyond the standard proj and inv proj mats are special cases.  Please setup special uniforms accordingly in the future.
            if (shader->getUniformLocation(LLShaderMgr::INVERSE_PROJECTION_MATRIX))
            {
                glh::matrix4f inv_proj = mat.inverse();
                shader->uniformMatrix4fv(LLShaderMgr::INVERSE_PROJECTION_MATRIX, 1, false, inv_proj.m);
            }

            // Used by some full screen effects - such as full screen lights, glow, etc.
            if (shader->getUniformLocation(LLShaderMgr::IDENTITY_MATRIX))
            {
                shader->uniformMatrix4fv(LLShaderMgr::IDENTITY_MATRIX, 1, GL_FALSE, glh::matrix4f::identity().m);
            }

            shader->uniformMatrix4fv(name[MM_PROJECTION], 1, GL_FALSE, mat.m);
            shader->mMatHash[MM_PROJECTION] = mMatHash[MM_PROJECTION];

            if (!mvp_done)
            {
                //update MVP matrix
                S32 loc = shader->getUniformLocation(LLShaderMgr::MODELVIEW_PROJECTION_MATRIX);
                if (loc > -1)
                {
                    if (cached_mvp_mdv_hash != mMatHash[MM_PROJECTION] || cached_mvp_proj_hash != mMatHash[MM_PROJECTION])
                    {
                        U32 mdv = MM_MODELVIEW;
                        cached_mvp = mat;
                        cached_mvp.mult_right(mMatrix[mdv][mMatIdx[mdv]]);
                        cached_mvp_mdv_hash = mMatHash[MM_MODELVIEW];
                        cached_mvp_proj_hash = mMatHash[MM_PROJECTION];
                    }

                    shader->uniformMatrix4fv(LLShaderMgr::MODELVIEW_PROJECTION_MATRIX, 1, GL_FALSE, cached_mvp.m);
                }
            }
        }

        for (i = MM_TEXTURE0; i < NUM_MATRIX_MODES; ++i)
        {
            if (mMatHash[i] != shader->mMatHash[i])
            {
                shader->uniformMatrix4fv(name[i], 1, GL_FALSE, mMatrix[i][mMatIdx[i]].m);
                shader->mMatHash[i] = mMatHash[i];
            }
        }


        if (shader->mFeatures.hasLighting || shader->mFeatures.calculatesLighting || shader->mFeatures.calculatesAtmospherics)
        { //also sync light state
            syncLightState();
        }
    }
    STOP_GLERROR;
}

void LLRender::translatef(const GLfloat& x, const GLfloat& y, const GLfloat& z)
{
    flush();

    {
        glh::matrix4f trans_mat(1,0,0,x,
                                0,1,0,y,
                                0,0,1,z,
                                0,0,0,1);

        mMatrix[mMatrixMode][mMatIdx[mMatrixMode]].mult_right(trans_mat);
        mMatHash[mMatrixMode]++;
    }
}

void LLRender::scalef(const GLfloat& x, const GLfloat& y, const GLfloat& z)
{
    flush();

    {
        glh::matrix4f scale_mat(x,0,0,0,
                                0,y,0,0,
                                0,0,z,0,
                                0,0,0,1);

        mMatrix[mMatrixMode][mMatIdx[mMatrixMode]].mult_right(scale_mat);
        mMatHash[mMatrixMode]++;
    }
}

void LLRender::ortho(F32 left, F32 right, F32 bottom, F32 top, F32 zNear, F32 zFar)
{
    flush();

    {

        glh::matrix4f ortho_mat(2.f/(right-left),0,0,   -(right+left)/(right-left),
                                0,2.f/(top-bottom),0,   -(top+bottom)/(top-bottom),
                                0,0,-2.f/(zFar-zNear),  -(zFar+zNear)/(zFar-zNear),
                                0,0,0,1);

        mMatrix[mMatrixMode][mMatIdx[mMatrixMode]].mult_right(ortho_mat);
        mMatHash[mMatrixMode]++;
    }
}

void LLRender::rotatef(const GLfloat& a, const GLfloat& x, const GLfloat& y, const GLfloat& z)
{
    flush();

    {
        F32 r = a * DEG_TO_RAD;

        F32 c = cosf(r);
        F32 s = sinf(r);

        F32 ic = 1.f-c;

        glh::matrix4f rot_mat(x*x*ic+c,     x*y*ic-z*s,     x*z*ic+y*s,     0,
                              x*y*ic+z*s,   y*y*ic+c,       y*z*ic-x*s,     0,
                              x*z*ic-y*s,   y*z*ic+x*s,     z*z*ic+c,       0,
                              0,0,0,1);

        mMatrix[mMatrixMode][mMatIdx[mMatrixMode]].mult_right(rot_mat);
        mMatHash[mMatrixMode]++;
    }
}

void LLRender::pushMatrix()
{
    flush();

    {
        if (mMatIdx[mMatrixMode] < LL_MATRIX_STACK_DEPTH-1)
        {
            mMatrix[mMatrixMode][mMatIdx[mMatrixMode]+1] = mMatrix[mMatrixMode][mMatIdx[mMatrixMode]];
            ++mMatIdx[mMatrixMode];
        }
        else
        {
            LL_WARNS() << "Matrix stack overflow." << LL_ENDL;
        }
    }
}

void LLRender::popMatrix()
{
    flush();
    {
        if (mMatIdx[mMatrixMode] > 0)
        {
            --mMatIdx[mMatrixMode];
            mMatHash[mMatrixMode]++;
        }
        else
        {
            LL_WARNS() << "Matrix stack underflow." << LL_ENDL;
        }
    }
}

void LLRender::loadMatrix(const GLfloat* m)
{
    flush();
    {
        mMatrix[mMatrixMode][mMatIdx[mMatrixMode]].set_value((GLfloat*) m);
        mMatHash[mMatrixMode]++;
    }
}

void LLRender::multMatrix(const GLfloat* m)
{
    flush();
    {
        glh::matrix4f mat((GLfloat*) m);

        mMatrix[mMatrixMode][mMatIdx[mMatrixMode]].mult_right(mat);
        mMatHash[mMatrixMode]++;
    }
}

void LLRender::matrixMode(eMatrixMode mode)
{
    if (mode == MM_TEXTURE)
    {
        U32 tex_index = gGL.getCurrentTexUnitIndex();
        // the shaders don't actually reference anything beyond texture_matrix0/1 outside of terrain rendering
        llassert(tex_index <= 3);
        mode = eMatrixMode(MM_TEXTURE0 + tex_index);
        if (mode > MM_TEXTURE3)
        {
            // getCurrentTexUnitIndex() can go as high as 32 (LL_NUM_TEXTURE_LAYERS)
            // Large value will result in a crash at mMatrix
            LL_WARNS_ONCE() << "Attempted to assign matrix mode out of bounds: " << mode << LL_ENDL;
            mode = MM_TEXTURE0;
        }
    }

    mMatrixMode = mode;
}

LLRender::eMatrixMode LLRender::getMatrixMode()
{
    if (mMatrixMode >= MM_TEXTURE0 && mMatrixMode <= MM_TEXTURE3)
    { //always return MM_TEXTURE if current matrix mode points at any texture matrix
        return MM_TEXTURE;
    }

    return mMatrixMode;
}


void LLRender::loadIdentity()
{
    flush();

    {
        llassert_always(mMatrixMode < NUM_MATRIX_MODES) ;

        mMatrix[mMatrixMode][mMatIdx[mMatrixMode]].make_identity();
        mMatHash[mMatrixMode]++;
    }
}

const glh::matrix4f& LLRender::getModelviewMatrix()
{
    return mMatrix[MM_MODELVIEW][mMatIdx[MM_MODELVIEW]];
}

const glh::matrix4f& LLRender::getProjectionMatrix()
{
    return mMatrix[MM_PROJECTION][mMatIdx[MM_PROJECTION]];
}

void LLRender::translateUI(F32 x, F32 y, F32 z)
{
    if (mUIOffset.empty())
    {
        LL_ERRS() << "Need to push a UI translation frame before offsetting" << LL_ENDL;
    }

    mUIOffset.back().mV[0] += x;
    mUIOffset.back().mV[1] += y;
    mUIOffset.back().mV[2] += z;
}

void LLRender::scaleUI(F32 x, F32 y, F32 z)
{
    if (mUIScale.empty())
    {
        LL_ERRS() << "Need to push a UI transformation frame before scaling." << LL_ENDL;
    }

    mUIScale.back().scaleVec(LLVector3(x,y,z));
}

void LLRender::pushUIMatrix()
{
    if (mUIOffset.empty())
    {
        mUIOffset.push_back(LLVector3(0,0,0));
    }
    else
    {
        mUIOffset.push_back(mUIOffset.back());
    }

    if (mUIScale.empty())
    {
        mUIScale.push_back(LLVector3(1,1,1));
    }
    else
    {
        mUIScale.push_back(mUIScale.back());
    }
}

void LLRender::popUIMatrix()
{
    if (mUIOffset.empty())
    {
        LL_ERRS() << "UI offset stack blown." << LL_ENDL;
    }
    mUIOffset.pop_back();
    mUIScale.pop_back();
}

LLVector3 LLRender::getUITranslation()
{
    if (mUIOffset.empty())
    {
        return LLVector3(0,0,0);
    }
    return mUIOffset.back();
}

LLVector3 LLRender::getUIScale()
{
    if (mUIScale.empty())
    {
        return LLVector3(1,1,1);
    }
    return mUIScale.back();
}


void LLRender::loadUIIdentity()
{
    if (mUIOffset.empty())
    {
        LL_ERRS() << "Need to push UI translation frame before clearing offset." << LL_ENDL;
    }
    mUIOffset.back().setVec(0,0,0);
    mUIScale.back().setVec(1,1,1);
}

void LLRender::setColorMask(bool writeColor, bool writeAlpha)
{
    setColorMask(writeColor, writeColor, writeColor, writeAlpha);
}

void LLRender::setColorMask(bool writeColorR, bool writeColorG, bool writeColorB, bool writeAlpha)
{
    flush();

    if (mCurrColorMask[0] != writeColorR ||
        mCurrColorMask[1] != writeColorG ||
        mCurrColorMask[2] != writeColorB ||
        mCurrColorMask[3] != writeAlpha)
    {
        mCurrColorMask[0] = writeColorR;
        mCurrColorMask[1] = writeColorG;
        mCurrColorMask[2] = writeColorB;
        mCurrColorMask[3] = writeAlpha;

        glColorMask(writeColorR ? GL_TRUE : GL_FALSE,
                    writeColorG ? GL_TRUE : GL_FALSE,
                    writeColorB ? GL_TRUE : GL_FALSE,
                    writeAlpha ? GL_TRUE : GL_FALSE);
    }
}

void LLRender::setSceneBlendType(eBlendType type)
{
    switch (type)
    {
        case BT_ALPHA:
            blendFunc(BF_SOURCE_ALPHA, BF_ONE_MINUS_SOURCE_ALPHA);
            break;
        case BT_ADD:
            blendFunc(BF_ONE, BF_ONE);
            break;
        case BT_ADD_WITH_ALPHA:
            blendFunc(BF_SOURCE_ALPHA, BF_ONE);
            break;
        case BT_MULT:
            blendFunc(BF_DEST_COLOR, BF_ZERO);
            break;
        case BT_MULT_ALPHA:
            blendFunc(BF_DEST_ALPHA, BF_ZERO);
            break;
        case BT_MULT_X2:
            blendFunc(BF_DEST_COLOR, BF_SOURCE_COLOR);
            break;
        case BT_REPLACE:
            blendFunc(BF_ONE, BF_ZERO);
            break;
        default:
            LL_ERRS() << "Unknown Scene Blend Type: " << type << LL_ENDL;
            break;
    }
}

void LLRender::blendFunc(eBlendFactor sfactor, eBlendFactor dfactor)
{
    llassert(sfactor < BF_UNDEF);
    llassert(dfactor < BF_UNDEF);
    if (mCurrBlendColorSFactor != sfactor || mCurrBlendColorDFactor != dfactor ||
        mCurrBlendAlphaSFactor != sfactor || mCurrBlendAlphaDFactor != dfactor)
    {
        mCurrBlendColorSFactor = sfactor;
        mCurrBlendAlphaSFactor = sfactor;
        mCurrBlendColorDFactor = dfactor;
        mCurrBlendAlphaDFactor = dfactor;
        flush();
        glBlendFunc(sGLBlendFactor[sfactor], sGLBlendFactor[dfactor]);
    }
}

void LLRender::blendFunc(eBlendFactor color_sfactor, eBlendFactor color_dfactor,
             eBlendFactor alpha_sfactor, eBlendFactor alpha_dfactor)
{
    llassert(color_sfactor < BF_UNDEF);
    llassert(color_dfactor < BF_UNDEF);
    llassert(alpha_sfactor < BF_UNDEF);
    llassert(alpha_dfactor < BF_UNDEF);

    if (mCurrBlendColorSFactor != color_sfactor || mCurrBlendColorDFactor != color_dfactor ||
        mCurrBlendAlphaSFactor != alpha_sfactor || mCurrBlendAlphaDFactor != alpha_dfactor)
    {
        mCurrBlendColorSFactor = color_sfactor;
        mCurrBlendAlphaSFactor = alpha_sfactor;
        mCurrBlendColorDFactor = color_dfactor;
        mCurrBlendAlphaDFactor = alpha_dfactor;
        flush();

        glBlendFuncSeparate(sGLBlendFactor[color_sfactor], sGLBlendFactor[color_dfactor],
                           sGLBlendFactor[alpha_sfactor], sGLBlendFactor[alpha_dfactor]);
    }
}

LLTexUnit* LLRender::getTexUnit(U32 index)
{
    if (index < mTexUnits.size())
    {
        return &mTexUnits[index];
    }
    else
    {
        LL_DEBUGS() << "Non-existing texture unit layer requested: " << index << LL_ENDL;
        return &mDummyTexUnit;
    }
}

LLLightState* LLRender::getLight(U32 index)
{
    if (index < mLightState.size())
    {
        return &mLightState[index];
    }

    return NULL;
}

void LLRender::setAmbientLightColor(const LLColor4& color)
{
    LL_PROFILE_ZONE_SCOPED_CATEGORY_PIPELINE;
    if (color != mAmbientLightColor)
    {
        ++mLightHash;
        mAmbientLightColor = color;
    }
}

bool LLRender::verifyTexUnitActive(U32 unitToVerify)
{
    if (mCurrTextureUnitIndex == unitToVerify)
    {
        return true;
    }
    else
    {
        LL_WARNS() << "TexUnit currently active: " << mCurrTextureUnitIndex << " (expecting " << unitToVerify << ")" << LL_ENDL;
        return false;
    }
}

void LLRender::clearErrors()
{
    while (glGetError())
    {
        //loop until no more error flags left
    }
}

void LLRender::begin(const GLuint& mode)
{
    if (mode != mMode)
    {
        if (mode == LLRender::QUADS)
        {
            mQuadCycle = 1;
        }

        if (mMode == LLRender::QUADS ||
            mMode == LLRender::LINES ||
            mMode == LLRender::TRIANGLES ||
            mMode == LLRender::POINTS)
        {
            flush();
        }
        else if (mCount != 0)
        {
            LL_ERRS() << "gGL.begin() called redundantly." << LL_ENDL;
        }

        mMode = mode;
    }
}

void LLRender::end()
{
    if (mCount == 0)
    {
        return;
        //IMM_ERRS << "GL begin and end called with no vertices specified." << LL_ENDL;
    }

    if ((mMode != LLRender::QUADS &&
        mMode != LLRender::LINES &&
        mMode != LLRender::TRIANGLES &&
        mMode != LLRender::POINTS) ||
        mCount > 2048)
    {
        flush();
    }
}
void LLRender::flush()
{
    STOP_GLERROR;
    if (mCount > 0)
    {
        LL_PROFILE_ZONE_SCOPED_CATEGORY_PIPELINE;
        llassert(LLGLSLShader::sCurBoundShaderPtr != nullptr);
        if (!mUIOffset.empty())
        {
            sUICalls++;
            sUIVerts += mCount;
        }

        //store mCount in a local variable to avoid re-entrance (drawArrays may call flush)
        U32 count = mCount;

            if (mMode == LLRender::QUADS && !sGLCoreProfile)
            {
                if (mCount%4 != 0)
                {
                count -= (mCount % 4);
                LL_WARNS() << "Incomplete quad requested." << LL_ENDL;
                }
            }

            if (mMode == LLRender::TRIANGLES)
            {
                if (mCount%3 != 0)
                {
                count -= (mCount % 3);
                LL_WARNS() << "Incomplete triangle requested." << LL_ENDL;
                }
            }

            if (mMode == LLRender::LINES)
            {
                if (mCount%2 != 0)
                {
                count -= (mCount % 2);
                LL_WARNS() << "Incomplete line requested." << LL_ENDL;
            }
        }

        mCount = 0;

        if (mBuffer)
        {

            HBXXH64 hash;
            U32 attribute_mask = LLGLSLShader::sCurBoundShaderPtr->mAttributeMask;

            {
                LL_PROFILE_ZONE_NAMED_CATEGORY_VERTEX("vb cache hash");

                hash.update((U8*)mVerticesp.get(), count * sizeof(LLVector4a));
                if (attribute_mask & LLVertexBuffer::MAP_TEXCOORD0)
                {
                    hash.update((U8*)mTexcoordsp.get(), count * sizeof(LLVector2));
                }

                if (attribute_mask & LLVertexBuffer::MAP_COLOR)
                {
                    hash.update((U8*)mColorsp.get(), count * sizeof(LLColor4U));
                }

                hash.finalize();
            }


            U64 vhash = hash.digest();

            // check the VB cache before making a new vertex buffer
            // This is a giant hack to deal with (mostly) our terrible UI rendering code
            // that was built on top of OpenGL immediate mode.  Huge performance wins
            // can be had by not uploading geometry to VRAM unless absolutely necessary.
            // Most of our usage of the "immediate mode" style draw calls is actually
            // sending the same geometry over and over again.
            // To leverage this, we maintain a running hash of the vertex stream being
            // built up before a flush, and then check that hash against a VB
            // cache just before creating a vertex buffer in VRAM
            std::unordered_map<U64, LLVBCache>::iterator cache = sVBCache.find(vhash);

            LLPointer<LLVertexBuffer> vb;

            if (cache != sVBCache.end())
            {
                LL_PROFILE_ZONE_NAMED_CATEGORY_VERTEX("vb cache hit");
                // cache hit, just use the cached buffer
                vb = cache->second.vb;
                cache->second.touched = std::chrono::steady_clock::now();
            }
            else
            {
                LL_PROFILE_ZONE_NAMED_CATEGORY_VERTEX("vb cache miss");
                vb = new LLVertexBuffer(attribute_mask);
                vb->allocateBuffer(count, 0);

                vb->setBuffer();

                vb->setPositionData((LLVector4a*) mVerticesp.get());

                if (attribute_mask & LLVertexBuffer::MAP_TEXCOORD0)
                {
                    vb->setTexCoord0Data(mTexcoordsp.get());
                }

                if (attribute_mask & LLVertexBuffer::MAP_COLOR)
                {
                    vb->setColorData(mColorsp.get());
                }

#if LL_DARWIN
                vb->unmapBuffer();
#endif
                vb->unbind();

                sVBCache[vhash] = { vb , std::chrono::steady_clock::now() };

                static U32 miss_count = 0;
                miss_count++;
                if (miss_count > 1024)
                {
                    LL_PROFILE_ZONE_NAMED_CATEGORY_VERTEX("vb cache clean");
                    miss_count = 0;
                    auto now = std::chrono::steady_clock::now();

                    using namespace std::chrono_literals;
                    // every 1024 misses, clean the cache of any VBs that haven't been touched in the last second
                    for (std::unordered_map<U64, LLVBCache>::iterator iter = sVBCache.begin(); iter != sVBCache.end(); )
                    {
                        if (now - iter->second.touched > 1s)
                        {
                            iter = sVBCache.erase(iter);
                        }
                        else
                        {
                            ++iter;
                        }
                    }
                }
            }

            vb->setBuffer();

            if (mMode == LLRender::QUADS && sGLCoreProfile)
            {
                vb->drawArrays(LLRender::TRIANGLES, 0, count);
                mQuadCycle = 1;
            }
            else
            {
                vb->drawArrays(mMode, 0, count);
            }
        }
        else
        {
            // mBuffer is present in main thread and not present in an image thread
            LL_ERRS() << "A flush call from outside main rendering thread" << LL_ENDL;
        }


        mVerticesp[0] = mVerticesp[count];
        mTexcoordsp[0] = mTexcoordsp[count];
        mColorsp[0] = mColorsp[count];

        mCount = 0;
    }
}

void LLRender::vertex3f(const GLfloat& x, const GLfloat& y, const GLfloat& z)
{
    //the range of mVerticesp, mColorsp and mTexcoordsp is [0, 4095]
    if (mCount > 2048)
    { //break when buffer gets reasonably full to keep GL command buffers happy and avoid overflow below
        switch (mMode)
        {
            case LLRender::POINTS: flush(); break;
            case LLRender::TRIANGLES: if (mCount%3==0) flush(); break;
            case LLRender::QUADS: if(mCount%4 == 0) flush(); break;
            case LLRender::LINES: if (mCount%2 == 0) flush(); break;
        }
    }

    if (mCount > 4094)
    {
    //  LL_WARNS() << "GL immediate mode overflow.  Some geometry not drawn." << LL_ENDL;
        return;
    }

    if (mUIOffset.empty())
    {
        mVerticesp[mCount] = LLVector3(x,y,z);
    }
    else
    {
        LLVector3 vert = (LLVector3(x,y,z)+mUIOffset.back()).scaledVec(mUIScale.back());
        mVerticesp[mCount] = vert;
    }

    if (mMode == LLRender::QUADS && LLRender::sGLCoreProfile)
    {
        mQuadCycle++;
        if (mQuadCycle == 4)
        { //copy two vertices so fourth quad element will add a triangle
            mQuadCycle = 0;

            mCount++;
            mVerticesp[mCount] = mVerticesp[mCount-3];
            mColorsp[mCount] = mColorsp[mCount-3];
            mTexcoordsp[mCount] = mTexcoordsp[mCount-3];

            mCount++;
            mVerticesp[mCount] = mVerticesp[mCount-2];
            mColorsp[mCount] = mColorsp[mCount-2];
            mTexcoordsp[mCount] = mTexcoordsp[mCount-2];
        }
    }

    mCount++;
    mVerticesp[mCount] = mVerticesp[mCount-1];
    mColorsp[mCount] = mColorsp[mCount-1];
    mTexcoordsp[mCount] = mTexcoordsp[mCount-1];
}

void LLRender::vertexBatchPreTransformed(LLVector3* verts, S32 vert_count)
{
    if (mCount + vert_count > 4094)
    {
        //  LL_WARNS() << "GL immediate mode overflow.  Some geometry not drawn." << LL_ENDL;
        return;
    }

    if (sGLCoreProfile && mMode == LLRender::QUADS)
    { //quads are deprecated, convert to triangle list
        S32 i = 0;

        while (i < vert_count)
        {
            //read first three
            mVerticesp[mCount++] = verts[i++];
            mTexcoordsp[mCount] = mTexcoordsp[mCount-1];
            mColorsp[mCount] = mColorsp[mCount-1];

            mVerticesp[mCount++] = verts[i++];
            mTexcoordsp[mCount] = mTexcoordsp[mCount-1];
            mColorsp[mCount] = mColorsp[mCount-1];

            mVerticesp[mCount++] = verts[i++];
            mTexcoordsp[mCount] = mTexcoordsp[mCount-1];
            mColorsp[mCount] = mColorsp[mCount-1];

            //copy two
            mVerticesp[mCount++] = verts[i-3];
            mTexcoordsp[mCount] = mTexcoordsp[mCount-1];
            mColorsp[mCount] = mColorsp[mCount-1];

            mVerticesp[mCount++] = verts[i-1];
            mTexcoordsp[mCount] = mTexcoordsp[mCount-1];
            mColorsp[mCount] = mColorsp[mCount-1];

            //copy last one
            mVerticesp[mCount++] = verts[i++];
            mTexcoordsp[mCount] = mTexcoordsp[mCount-1];
            mColorsp[mCount] = mColorsp[mCount-1];
        }
    }
    else
    {
        for (S32 i = 0; i < vert_count; i++)
        {
            mVerticesp[mCount] = verts[i];

            mCount++;
            mTexcoordsp[mCount] = mTexcoordsp[mCount-1];
            mColorsp[mCount] = mColorsp[mCount-1];
        }
    }

    if( mCount > 0 ) // ND: Guard against crashes if mCount is zero, yes it can happen
        mVerticesp[mCount] = mVerticesp[mCount-1];
}

void LLRender::vertexBatchPreTransformed(LLVector3* verts, LLVector2* uvs, S32 vert_count)
{
    if (mCount + vert_count > 4094)
    {
        //  LL_WARNS() << "GL immediate mode overflow.  Some geometry not drawn." << LL_ENDL;
        return;
    }

    if (sGLCoreProfile && mMode == LLRender::QUADS)
    { //quads are deprecated, convert to triangle list
        S32 i = 0;

        while (i < vert_count)
        {
            //read first three
            mVerticesp[mCount] = verts[i];
            mTexcoordsp[mCount++] = uvs[i++];
            mColorsp[mCount] = mColorsp[mCount-1];

            mVerticesp[mCount] = verts[i];
            mTexcoordsp[mCount++] = uvs[i++];
            mColorsp[mCount] = mColorsp[mCount-1];

            mVerticesp[mCount] = verts[i];
            mTexcoordsp[mCount++] = uvs[i++];
            mColorsp[mCount] = mColorsp[mCount-1];

            //copy last two
            mVerticesp[mCount] = verts[i-3];
            mTexcoordsp[mCount++] = uvs[i-3];
            mColorsp[mCount] = mColorsp[mCount-1];

            mVerticesp[mCount] = verts[i-1];
            mTexcoordsp[mCount++] = uvs[i-1];
            mColorsp[mCount] = mColorsp[mCount-1];

            //copy last one
            mVerticesp[mCount] = verts[i];
            mTexcoordsp[mCount++] = uvs[i++];
            mColorsp[mCount] = mColorsp[mCount-1];
        }
    }
    else
    {
        for (S32 i = 0; i < vert_count; i++)
        {
            mVerticesp[mCount] = verts[i];
            mTexcoordsp[mCount] = uvs[i];

            mCount++;
            mColorsp[mCount] = mColorsp[mCount-1];
        }
    }

    if (mCount > 0)
    {
        mVerticesp[mCount] = mVerticesp[mCount - 1];
        mTexcoordsp[mCount] = mTexcoordsp[mCount - 1];
    }
}

void LLRender::vertexBatchPreTransformed(LLVector3* verts, LLVector2* uvs, LLColor4U* colors, S32 vert_count)
{
    if (mCount + vert_count > 4094)
    {
        //  LL_WARNS() << "GL immediate mode overflow.  Some geometry not drawn." << LL_ENDL;
        return;
    }


    if (sGLCoreProfile && mMode == LLRender::QUADS)
    { //quads are deprecated, convert to triangle list
        S32 i = 0;

        while (i < vert_count)
        {
            //read first three
            mVerticesp[mCount] = verts[i];
            mTexcoordsp[mCount] = uvs[i];
            mColorsp[mCount++] = colors[i++];

            mVerticesp[mCount] = verts[i];
            mTexcoordsp[mCount] = uvs[i];
            mColorsp[mCount++] = colors[i++];

            mVerticesp[mCount] = verts[i];
            mTexcoordsp[mCount] = uvs[i];
            mColorsp[mCount++] = colors[i++];

            //copy last two
            mVerticesp[mCount] = verts[i-3];
            mTexcoordsp[mCount] = uvs[i-3];
            mColorsp[mCount++] = colors[i-3];

            mVerticesp[mCount] = verts[i-1];
            mTexcoordsp[mCount] = uvs[i-1];
            mColorsp[mCount++] = colors[i-1];

            //copy last one
            mVerticesp[mCount] = verts[i];
            mTexcoordsp[mCount] = uvs[i];
            mColorsp[mCount++] = colors[i++];
        }
    }
    else
    {
        for (S32 i = 0; i < vert_count; i++)
        {
            mVerticesp[mCount] = verts[i];
            mTexcoordsp[mCount] = uvs[i];
            mColorsp[mCount] = colors[i];

            mCount++;
        }
    }

    if (mCount > 0)
    {
        mVerticesp[mCount] = mVerticesp[mCount - 1];
        mTexcoordsp[mCount] = mTexcoordsp[mCount - 1];
        mColorsp[mCount] = mColorsp[mCount - 1];
    }
}

void LLRender::vertex2i(const GLint& x, const GLint& y)
{
    vertex3f((GLfloat) x, (GLfloat) y, 0);
}

void LLRender::vertex2f(const GLfloat& x, const GLfloat& y)
{
    vertex3f(x,y,0);
}

void LLRender::vertex2fv(const GLfloat* v)
{
    vertex3f(v[0], v[1], 0);
}

void LLRender::vertex3fv(const GLfloat* v)
{
    vertex3f(v[0], v[1], v[2]);
}

void LLRender::texCoord2f(const GLfloat& x, const GLfloat& y)
{
    mTexcoordsp[mCount] = LLVector2(x,y);
}

void LLRender::texCoord2i(const GLint& x, const GLint& y)
{
    texCoord2f((GLfloat) x, (GLfloat) y);
}

void LLRender::texCoord2fv(const GLfloat* tc)
{
    texCoord2f(tc[0], tc[1]);
}

void LLRender::color4ub(const GLubyte& r, const GLubyte& g, const GLubyte& b, const GLubyte& a)
{
    if (!LLGLSLShader::sCurBoundShaderPtr || LLGLSLShader::sCurBoundShaderPtr->mAttributeMask & LLVertexBuffer::MAP_COLOR)
    {
        mColorsp[mCount] = LLColor4U(r,g,b,a);
    }
    else
    { //not using shaders or shader reads color from a uniform
        diffuseColor4ub(r,g,b,a);
    }
}
void LLRender::color4ubv(const GLubyte* c)
{
    color4ub(c[0], c[1], c[2], c[3]);
}

void LLRender::color4f(const GLfloat& r, const GLfloat& g, const GLfloat& b, const GLfloat& a)
{
    color4ub((GLubyte) (llclamp(r, 0.f, 1.f)*255),
        (GLubyte) (llclamp(g, 0.f, 1.f)*255),
        (GLubyte) (llclamp(b, 0.f, 1.f)*255),
        (GLubyte) (llclamp(a, 0.f, 1.f)*255));
}

void LLRender::color4fv(const GLfloat* c)
{
    color4f(c[0],c[1],c[2],c[3]);
}

void LLRender::color3f(const GLfloat& r, const GLfloat& g, const GLfloat& b)
{
    color4f(r,g,b,1);
}

void LLRender::color3fv(const GLfloat* c)
{
    color4f(c[0],c[1],c[2],1);
}

void LLRender::diffuseColor3f(F32 r, F32 g, F32 b)
{
    LLGLSLShader* shader = LLGLSLShader::sCurBoundShaderPtr;
    llassert(shader != NULL);

    if (shader)
    {
        shader->uniform4f(LLShaderMgr::DIFFUSE_COLOR, r,g,b,1.f);
    }
}

void LLRender::diffuseColor3fv(const F32* c)
{
    LLGLSLShader* shader = LLGLSLShader::sCurBoundShaderPtr;
    llassert(shader != NULL);

    if (shader)
    {
        shader->uniform4f(LLShaderMgr::DIFFUSE_COLOR, c[0], c[1], c[2], 1.f);
    }
}

void LLRender::diffuseColor4f(F32 r, F32 g, F32 b, F32 a)
{
    LLGLSLShader* shader = LLGLSLShader::sCurBoundShaderPtr;
    llassert(shader != NULL);

    if (shader)
    {
        shader->uniform4f(LLShaderMgr::DIFFUSE_COLOR, r,g,b,a);
    }
}

void LLRender::diffuseColor4fv(const F32* c)
{
    LLGLSLShader* shader = LLGLSLShader::sCurBoundShaderPtr;
    llassert(shader != NULL);

    if (shader)
    {
        shader->uniform4fv(LLShaderMgr::DIFFUSE_COLOR, 1, c);
    }
}

void LLRender::diffuseColor4ubv(const U8* c)
{
    LLGLSLShader* shader = LLGLSLShader::sCurBoundShaderPtr;
    llassert(shader != NULL);

    if (shader)
    {
        shader->uniform4f(LLShaderMgr::DIFFUSE_COLOR, c[0]/255.f, c[1]/255.f, c[2]/255.f, c[3]/255.f);
    }
}

void LLRender::diffuseColor4ub(U8 r, U8 g, U8 b, U8 a)
{
    LLGLSLShader* shader = LLGLSLShader::sCurBoundShaderPtr;
    llassert(shader != NULL);

    if (shader)
    {
        shader->uniform4f(LLShaderMgr::DIFFUSE_COLOR, r/255.f, g/255.f, b/255.f, a/255.f);
    }
}


void LLRender::debugTexUnits(void)
{
    LL_INFOS("TextureUnit") << "Active TexUnit: " << mCurrTextureUnitIndex << LL_ENDL;
    std::string active_enabled = "false";
    for (U32 i = 0; i < mTexUnits.size(); i++)
    {
        if (getTexUnit(i)->mCurrTexType != LLTexUnit::TT_NONE)
        {
            if (i == mCurrTextureUnitIndex) active_enabled = "true";
            LL_INFOS("TextureUnit") << "TexUnit: " << i << " Enabled" << LL_ENDL;
            LL_INFOS("TextureUnit") << "Enabled As: " ;
            switch (getTexUnit(i)->mCurrTexType)
            {
                case LLTexUnit::TT_TEXTURE:
                    LL_CONT << "Texture 2D";
                    break;
                case LLTexUnit::TT_RECT_TEXTURE:
                    LL_CONT << "Texture Rectangle";
                    break;
                case LLTexUnit::TT_CUBE_MAP:
                    LL_CONT << "Cube Map";
                    break;
                default:
                    LL_CONT << "ARGH!!! NONE!";
                    break;
            }
            LL_CONT << ", Texture Bound: " << getTexUnit(i)->mCurrTexture << LL_ENDL;
        }
    }
    LL_INFOS("TextureUnit") << "Active TexUnit Enabled : " << active_enabled << LL_ENDL;
}



glh::matrix4f copy_matrix(F32* src)
{
    glh::matrix4f ret;
    ret.set_value(src);
    return ret;
}

glh::matrix4f get_current_modelview()
{
    return copy_matrix(gGLModelView);
}

glh::matrix4f get_current_projection()
{
    return copy_matrix(gGLProjection);
}

glh::matrix4f get_last_modelview()
{
    return copy_matrix(gGLLastModelView);
}

glh::matrix4f get_last_projection()
{
    return copy_matrix(gGLLastProjection);
}

void copy_matrix(const glh::matrix4f& src, F32* dst)
{
    for (U32 i = 0; i < 16; i++)
    {
        dst[i] = src.m[i];
    }
}

void set_current_modelview(const glh::matrix4f& mat)
{
    copy_matrix(mat, gGLModelView);
}

void set_current_projection(glh::matrix4f& mat)
{
    copy_matrix(mat, gGLProjection);
}

glh::matrix4f gl_ortho(GLfloat left, GLfloat right, GLfloat bottom, GLfloat top, GLfloat znear, GLfloat zfar)
{
    glh::matrix4f ret(
        2.f/(right-left), 0.f, 0.f, -(right+left)/(right-left),
        0.f, 2.f/(top-bottom), 0.f, -(top+bottom)/(top-bottom),
        0.f, 0.f, -2.f/(zfar-znear),  -(zfar+znear)/(zfar-znear),
        0.f, 0.f, 0.f, 1.f);

    return ret;
}

glh::matrix4f gl_perspective(GLfloat fovy, GLfloat aspect, GLfloat zNear, GLfloat zFar)
{
    GLfloat f = 1.f/tanf(DEG_TO_RAD*fovy/2.f);

    return glh::matrix4f(f/aspect, 0, 0, 0,
                         0, f, 0, 0,
                         0, 0, (zFar+zNear)/(zNear-zFar), (2.f*zFar*zNear)/(zNear-zFar),
                         0, 0, -1.f, 0);
}

glh::matrix4f gl_lookat(LLVector3 eye, LLVector3 center, LLVector3 up)
{
    LLVector3 f = center-eye;
    f.normVec();
    up.normVec();
    LLVector3 s = f % up;
    LLVector3 u = s % f;

    return glh::matrix4f(s[0], s[1], s[2], 0,
                      u[0], u[1], u[2], 0,
                      -f[0], -f[1], -f[2], 0,
                      0, 0, 0, 1);

}