/** 
 * @file llvlcomposition.cpp
 * @brief Viewer-side representation of a composition layer...
 *
 * $LicenseInfo:firstyear=2001&license=viewerlgpl$
 * 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 "llviewerprecompiledheaders.h"

#include "llvlcomposition.h"

#include <functional>

#include "llerror.h"
#include "v3math.h"
#include "llsurface.h"
#include "lltextureview.h"
#include "llviewertexture.h"
#include "llviewertexturelist.h"
#include "llfetchedgltfmaterial.h"
#include "llgltfmateriallist.h"
#include "llviewerregion.h"
#include "noise.h"
#include "llregionhandle.h" // for from_region_handle
#include "llviewercontrol.h"


extern LLColor4U MAX_WATER_COLOR;

static const U32 BASE_SIZE = 128;
static const F32 TERRAIN_DECODE_PRIORITY = 2048.f * 2048.f;

namespace
{
    F32 bilinear(const F32 v00, const F32 v01, const F32 v10, const F32 v11, const F32 x_frac, const F32 y_frac)
    {
        // Not sure if this is the right math...
        // Take weighted average of all four points (bilinear interpolation)
        F32 result;

        const F32 inv_x_frac = 1.f - x_frac;
        const F32 inv_y_frac = 1.f - y_frac;
        result = inv_x_frac*inv_y_frac*v00
                + x_frac*inv_y_frac*v10
                + inv_x_frac*y_frac*v01
                + x_frac*y_frac*v11;

        return result;
    }

    void boost_minimap_texture(LLViewerFetchedTexture* tex, F32 virtual_size)
    {
        llassert(tex);
        if (!tex) { return; }

        tex->setBoostLevel(LLGLTexture::BOOST_TERRAIN); // in case the raw image is at low detail
        tex->addTextureStats(virtual_size); // priority
    }

    void boost_minimap_material(LLFetchedGLTFMaterial* mat, F32 virtual_size)
    {
        if (!mat) { return; }
        if (mat->mBaseColorTexture) { boost_minimap_texture(mat->mBaseColorTexture, virtual_size); }
        if (mat->mNormalTexture) { boost_minimap_texture(mat->mNormalTexture, virtual_size); }
        if (mat->mMetallicRoughnessTexture) { boost_minimap_texture(mat->mMetallicRoughnessTexture, virtual_size); }
        if (mat->mEmissiveTexture) { boost_minimap_texture(mat->mEmissiveTexture, virtual_size); }
    }

    void unboost_minimap_texture(LLViewerFetchedTexture* tex)
    {
        if (!tex) { return; }
        tex->setBoostLevel(LLGLTexture::BOOST_NONE);
        tex->setMinDiscardLevel(MAX_DISCARD_LEVEL + 1);
    }

    void unboost_minimap_material(LLFetchedGLTFMaterial* mat)
    {
        if (!mat) { return; }
        if (mat->mBaseColorTexture) { unboost_minimap_texture(mat->mBaseColorTexture); }
        if (mat->mNormalTexture) { unboost_minimap_texture(mat->mNormalTexture); }
        if (mat->mMetallicRoughnessTexture) { unboost_minimap_texture(mat->mMetallicRoughnessTexture); }
        if (mat->mEmissiveTexture) { unboost_minimap_texture(mat->mEmissiveTexture); }
    }
};

LLTerrainMaterials::LLTerrainMaterials()
{
    for (S32 i = 0; i < ASSET_COUNT; ++i)
    {
        mMaterialTexturesSet[i] = false;
    }
}

LLTerrainMaterials::~LLTerrainMaterials()
{
    unboost();
}

BOOL LLTerrainMaterials::generateMaterials()
{
    if (texturesReady(true, true))
    {
        return TRUE;
    }

    if (materialsReady(true, true))
    {
        return TRUE;
    }

    return FALSE;
}

void LLTerrainMaterials::boost()
{
    for (S32 i = 0; i < ASSET_COUNT; ++i)
    {
        LLPointer<LLViewerFetchedTexture>& tex = mDetailTextures[i];
        llassert(tex.notNull());
        boost_minimap_texture(tex, TERRAIN_DECODE_PRIORITY);

        LLPointer<LLFetchedGLTFMaterial>& mat = mDetailMaterials[i];
        boost_minimap_material(mat, TERRAIN_DECODE_PRIORITY);
    }
}

void LLTerrainMaterials::unboost()
{
    for (S32 i = 0; i < ASSET_COUNT; ++i)
    {
        LLPointer<LLViewerFetchedTexture>& tex = mDetailTextures[i];
        unboost_minimap_texture(tex);

        LLPointer<LLFetchedGLTFMaterial>& mat = mDetailMaterials[i];
        unboost_minimap_material(mat);
    }
}

LLUUID LLTerrainMaterials::getDetailAssetID(S32 asset)
{
    llassert(mDetailTextures[asset] && mDetailMaterials[asset]);
    // Assume both the the material and texture were fetched in the same way
    // using the same UUID. However, we may not know at this point which one
    // will load.
	return mDetailTextures[asset] ? mDetailTextures[asset]->getID() : LLUUID::null;
}

LLPointer<LLViewerFetchedTexture> fetch_terrain_texture(const LLUUID& id)
{
    if (id.isNull())
    {
        return nullptr;
    }

    LLPointer<LLViewerFetchedTexture> tex = LLViewerTextureManager::getFetchedTexture(id);
    return tex;
}

void LLTerrainMaterials::setDetailAssetID(S32 asset, const LLUUID& id)
{
    // *NOTE: If there were multiple terrain swatches using the same asset
    // ID, the asset still in use will be temporarily unboosted.
    // It will be boosted again during terrain rendering.
    unboost_minimap_texture(mDetailTextures[asset]);
    unboost_minimap_material(mDetailMaterials[asset]);

	// This is terrain texture, but we are not setting it as BOOST_TERRAIN
	// since we will be manipulating it later as needed.
	mDetailTextures[asset] = fetch_terrain_texture(id);
    LLPointer<LLFetchedGLTFMaterial>& mat = mDetailMaterials[asset];
    mat = id.isNull() ? nullptr : gGLTFMaterialList.getMaterial(id);
    mMaterialTexturesSet[asset] = false;
}

LLTerrainMaterials::Type LLTerrainMaterials::getMaterialType()
{
	LL_PROFILE_ZONE_SCOPED;

    const BOOL use_textures = texturesReady(false, false) || !materialsReady(false, false);
    return use_textures ? Type::TEXTURE : Type::PBR;
}

bool LLTerrainMaterials::texturesReady(bool boost, bool strict)
{
    bool ready[ASSET_COUNT];
    // *NOTE: Calls to textureReady may boost textures. Do not early-return.
    for (S32 i = 0; i < ASSET_COUNT; i++)
    {
        ready[i] = mDetailTextures[i].notNull() && textureReady(mDetailTextures[i], boost);
    }

    bool one_ready = false;
    for (S32 i = 0; i < ASSET_COUNT; i++)
    {
        const bool current_ready = ready[i];
        one_ready = one_ready || current_ready;
        if (!current_ready && strict)
        {
            return false;
        }
    }
    return one_ready;
}

bool LLTerrainMaterials::materialsReady(bool boost, bool strict)
{
    bool ready[ASSET_COUNT];
    // *NOTE: Calls to materialReady may boost materials/textures. Do not early-return.
    for (S32 i = 0; i < ASSET_COUNT; i++)
    {
        ready[i] = materialReady(mDetailMaterials[i], mMaterialTexturesSet[i], boost, strict);
    }

#if 1
    static LLCachedControl<bool> sRenderTerrainPBREnabled(gSavedSettings, "RenderTerrainPBREnabled", false);
    static LLCachedControl<bool> sRenderTerrainPBRForce(gSavedSettings, "RenderTerrainPBRForce", false);
    if (sRenderTerrainPBREnabled && sRenderTerrainPBRForce)
    {
        bool defined = true;
        for (S32 i = 0; i < ASSET_COUNT; i++)
        {
            if (!mDetailMaterials[i])
            {
                defined = false;
                break;
            }
        }
        if (defined)
        {
            return true;
        }
    }
#endif

    bool one_ready = false;
    for (S32 i = 0; i < ASSET_COUNT; i++)
    {
        const bool current_ready = ready[i];
        one_ready = one_ready || current_ready;
        if (!current_ready && strict)
        {
            return false;
        }
    }
    return one_ready;
}

// Boost the texture loading priority
// Return true when ready to use (i.e. texture is sufficiently loaded)
// static
bool LLTerrainMaterials::textureReady(LLPointer<LLViewerFetchedTexture>& tex, bool boost)
{
    llassert(tex);
    if (!tex) { return false; }

    if (tex->getDiscardLevel() < 0)
    {
        if (boost)
        {
            boost_minimap_texture(tex, BASE_SIZE*BASE_SIZE);
        }
        return false;
    }
    if ((tex->getDiscardLevel() != 0 &&
         (tex->getWidth() < BASE_SIZE ||
          tex->getHeight() < BASE_SIZE)))
    {
        if (boost)
        {
            boost_minimap_texture(tex, BASE_SIZE*BASE_SIZE);

            S32 width = tex->getFullWidth();
            S32 height = tex->getFullHeight();
            S32 min_dim = llmin(width, height);
            S32 ddiscard = 0;
            while (min_dim > BASE_SIZE && ddiscard < MAX_DISCARD_LEVEL)
            {
                ddiscard++;
                min_dim /= 2;
            }
            tex->setMinDiscardLevel(ddiscard);
        }
        return false;
    }
    if (tex->getComponents() == 0)
    {
        return false;
    }
    return true;
}

// Boost the loading priority of every known texture in the material
// Return true when ready to use
// static
bool LLTerrainMaterials::materialReady(LLPointer<LLFetchedGLTFMaterial> &mat, bool &textures_set, bool boost, bool strict)
{
    if (!mat || !mat->isLoaded())
    {
        return false;
    }

    // Material is loaded, but textures may not be
    if (!textures_set)
    {
        textures_set = true;
        // *NOTE: These can sometimes be set to to nullptr due to
        // updateTEMaterialTextures. For the sake of robustness, we emulate
        // that fetching behavior by setting textures of null IDs to nullptr.
        mat->mBaseColorTexture         = fetch_terrain_texture(mat->mTextureId[LLGLTFMaterial::GLTF_TEXTURE_INFO_BASE_COLOR]);
        mat->mNormalTexture            = fetch_terrain_texture(mat->mTextureId[LLGLTFMaterial::GLTF_TEXTURE_INFO_NORMAL]);
        mat->mMetallicRoughnessTexture = fetch_terrain_texture(mat->mTextureId[LLGLTFMaterial::GLTF_TEXTURE_INFO_METALLIC_ROUGHNESS]);
        mat->mEmissiveTexture          = fetch_terrain_texture(mat->mTextureId[LLGLTFMaterial::GLTF_TEXTURE_INFO_EMISSIVE]);
    }

    // *NOTE: Calls to textureReady may boost textures. Do not early-return.
    bool ready[LLGLTFMaterial::GLTF_TEXTURE_INFO_COUNT];
    ready[LLGLTFMaterial::GLTF_TEXTURE_INFO_BASE_COLOR] =
        mat->mTextureId[LLGLTFMaterial::GLTF_TEXTURE_INFO_BASE_COLOR].isNull() || textureReady(mat->mBaseColorTexture, boost);
    ready[LLGLTFMaterial::GLTF_TEXTURE_INFO_NORMAL] =
        mat->mTextureId[LLGLTFMaterial::GLTF_TEXTURE_INFO_NORMAL].isNull() || textureReady(mat->mNormalTexture, boost);
    ready[LLGLTFMaterial::GLTF_TEXTURE_INFO_METALLIC_ROUGHNESS] =
        mat->mTextureId[LLGLTFMaterial::GLTF_TEXTURE_INFO_METALLIC_ROUGHNESS].isNull() ||
        textureReady(mat->mMetallicRoughnessTexture, boost);
    ready[LLGLTFMaterial::GLTF_TEXTURE_INFO_EMISSIVE] =
        mat->mTextureId[LLGLTFMaterial::GLTF_TEXTURE_INFO_EMISSIVE].isNull() || textureReady(mat->mEmissiveTexture, boost);

    if (strict)
    {
        for (U32 i = 0; i < LLGLTFMaterial::GLTF_TEXTURE_INFO_COUNT; ++i)
        {
            if (!ready[i])
            {
                return false;
            }
        }
    }

    return true;
}

// static
const LLUUID (&LLVLComposition::getDefaultTextures())[ASSET_COUNT]
{
    const static LLUUID default_textures[LLVLComposition::ASSET_COUNT] =
    {
        TERRAIN_DIRT_DETAIL,
        TERRAIN_GRASS_DETAIL,
        TERRAIN_MOUNTAIN_DETAIL,
        TERRAIN_ROCK_DETAIL
    };
    return default_textures;
}

LLVLComposition::LLVLComposition(LLSurface *surfacep, const U32 width, const F32 scale) :
    LLTerrainMaterials(),
	LLViewerLayer(width, scale),
	mParamsReady(false)
{
	// Load Terrain Textures - Original ones
    const LLUUID (&default_textures)[LLVLComposition::ASSET_COUNT] = LLVLComposition::getDefaultTextures();
    for (S32 i = 0; i < ASSET_COUNT; ++i)
    {
        setDetailAssetID(i, default_textures[i]);
    }

	mSurfacep = surfacep;

	// Initialize the texture matrix to defaults.
	for (S32 i = 0; i < CORNER_COUNT; ++i)
	{
		mStartHeight[i] = gSavedSettings.getF32("TerrainColorStartHeight");
		mHeightRange[i] = gSavedSettings.getF32("TerrainColorHeightRange");
	}
}


LLVLComposition::~LLVLComposition()
{
    LLTerrainMaterials::~LLTerrainMaterials();
}


void LLVLComposition::setSurface(LLSurface *surfacep)
{
	mSurfacep = surfacep;
}

bool LLVLComposition::generateHeights(const F32 x, const F32 y,
									  const F32 width, const F32 height)
{
	if (!mParamsReady)
	{
		// All the parameters haven't been set yet (we haven't gotten the message from the sim)
		return false;
	}

	llassert(mSurfacep);

	if (!mSurfacep || !mSurfacep->getRegion()) 
	{
		// We don't always have the region yet here....
		return false;
	}

	S32 x_begin, y_begin, x_end, y_end;

	x_begin = ll_round( x * mScaleInv );
	y_begin = ll_round( y * mScaleInv );
	x_end = ll_round( (x + width) * mScaleInv );
	y_end = ll_round( (y + width) * mScaleInv );

	if (x_end > mWidth)
	{
		x_end = mWidth;
	}
	if (y_end > mWidth)
	{
		y_end = mWidth;
	}

	LLVector3d origin_global = from_region_handle(mSurfacep->getRegion()->getHandle());

	// For perlin noise generation...
	const F32 slope_squared = 1.5f*1.5f;
	const F32 xyScale = 4.9215f; //0.93284f;
	const F32 zScale = 4; //0.92165f;
	const F32 z_offset = 0.f;
	const F32 noise_magnitude = 2.f;		//  Degree to which noise modulates composition layer (versus
											//  simple height)

	const F32 xyScaleInv = (1.f / xyScale);
	const F32 zScaleInv = (1.f / zScale);

	const F32 inv_width = 1.f/mWidth;

	// OK, for now, just have the composition value equal the height at the point.
	for (S32 j = y_begin; j < y_end; j++)
	{
		for (S32 i = x_begin; i < x_end; i++)
		{

			F32 vec[3];
			F32 vec1[3];
			F32 twiddle;

			// Bilinearly interpolate the start height and height range of the textures
			F32 start_height = bilinear(mStartHeight[SOUTHWEST],
										mStartHeight[SOUTHEAST],
										mStartHeight[NORTHWEST],
										mStartHeight[NORTHEAST],
										i*inv_width, j*inv_width); // These will be bilinearly interpolated
			F32 height_range = bilinear(mHeightRange[SOUTHWEST],
										mHeightRange[SOUTHEAST],
										mHeightRange[NORTHWEST],
										mHeightRange[NORTHEAST],
										i*inv_width, j*inv_width); // These will be bilinearly interpolated

			LLVector3 location(i*mScale, j*mScale, 0.f);

			F32 height = mSurfacep->resolveHeightRegion(location) + z_offset;

			// Step 0: Measure the exact height at this texel
			vec[0] = (F32)(origin_global.mdV[VX]+location.mV[VX])*xyScaleInv;	//  Adjust to non-integer lattice
			vec[1] = (F32)(origin_global.mdV[VY]+location.mV[VY])*xyScaleInv;
			vec[2] = height*zScaleInv;
			//
			//  Choose material value by adding to the exact height a random value 
			//
			vec1[0] = vec[0]*(0.2222222222f);
			vec1[1] = vec[1]*(0.2222222222f);
			vec1[2] = vec[2]*(0.2222222222f);
			twiddle = noise2(vec1)*6.5f;					//  Low freq component for large divisions

			twiddle += turbulence2(vec, 2)*slope_squared;	//  High frequency component
			twiddle *= noise_magnitude;

			F32 scaled_noisy_height = (height + twiddle - start_height) * F32(ASSET_COUNT) / height_range;

			scaled_noisy_height = llmax(0.f, scaled_noisy_height);
			scaled_noisy_height = llmin(3.f, scaled_noisy_height);
			*(mDatap + i + j*mWidth) = scaled_noisy_height;
		}
	}
	return true;
}

LLTerrainMaterials gLocalTerrainMaterials;

bool LLVLComposition::generateComposition()
{
	if (!mParamsReady)
	{
		// All the parameters haven't been set yet (we haven't gotten the message from the sim)
		return false;
	}

    return LLTerrainMaterials::generateMaterials();
}

namespace
{
    void prepare_fallback_image(LLImageRaw* raw_image)
    {
        raw_image->resize(BASE_SIZE, BASE_SIZE, 4);
        raw_image->fill(LLColor4U::white);
    }

    // Check if the raw image is loaded for this texture at a discard
    // level the minimap can use, and if not then try to get it loaded.
    bool prepare_raw_image(LLPointer<LLImageRaw>& raw_image, bool emissive, LLViewerFetchedTexture* tex, bool& delete_raw_post)
    {
        if (!tex)
        {
            if (!emissive)
            {
                prepare_fallback_image(raw_image);
            }
            else
            {
                llassert(!raw_image);
                raw_image = nullptr;
            }
            return true;
        }
        if (raw_image)
        {
            // Callback already initiated
            if (raw_image->getDataSize() > 0)
            {
                // Callback finished
                delete_raw_post = true;
                return true;
            }
            else
            {
                return false;
            }
        }

        raw_image = new LLImageRaw();

        S32 ddiscard = 0;
        {
            S32 min_dim = llmin(tex->getFullWidth(), tex->getFullHeight());
            while (min_dim > BASE_SIZE && ddiscard < MAX_DISCARD_LEVEL)
            {
                ddiscard++;
                min_dim /= 2;
            }
        }

        struct PendingImage
        {
            LLImageRaw* mRawImage;
            S32 mDesiredDiscard;
            LLUUID mTextureId;
            PendingImage(LLImageRaw* raw_image, S32 ddiscard, const LLUUID& texture_id)
                : mRawImage(raw_image)
                , mDesiredDiscard(ddiscard)
                , mTextureId(texture_id)
            {
                mRawImage->ref();
            }
            ~PendingImage()
            {
                mRawImage->unref();
            }
        };
        PendingImage* pending_image = new PendingImage(raw_image, ddiscard, tex->getID());

        loaded_callback_func cb = [](bool success, LLViewerFetchedTexture * src_vi, LLImageRaw * src, LLImageRaw * src_aux, S32 discard_level, bool is_final, void* userdata) {
            PendingImage* pending = (PendingImage*)userdata;
            // Owning LLVLComposition still exists

            // Assume mRawImage only used by single LLVLComposition for now
            const bool in_use_by_composition = pending->mRawImage->getNumRefs() > 1;
            llassert(pending->mRawImage->getNumRefs());
            llassert(pending->mRawImage->getNumRefs() <= 2);
            const bool needs_data = !pending->mRawImage->getDataSize();
            if (in_use_by_composition && needs_data)
            {
                if (success && pending->mDesiredDiscard == discard_level)
                {
                    pending->mRawImage->resize(BASE_SIZE, BASE_SIZE, src->getComponents());
                    pending->mRawImage->copyScaled(src);
                }
                else if (is_final)
                {
                    prepare_fallback_image(pending->mRawImage);
                }
            }

            if (is_final) { delete pending; }
        };
        tex->setLoadedCallback(cb, ddiscard, true, false, pending_image, nullptr);
        tex->forceToSaveRawImage(ddiscard);

        return false;
    }
};

bool LLVLComposition::generateMinimapTileLand(const F32 x, const F32 y,
									  const F32 width, const F32 height)
{
	LL_PROFILE_ZONE_SCOPED
	llassert(mSurfacep);
	llassert(x >= 0.f);
	llassert(y >= 0.f);

	///////////////////////////
	//
	// Generate raw data arrays for surface textures
	//
	//

	// These have already been validated by generateComposition.
	U8* st_data[ASSET_COUNT];
	S32 st_data_size[ASSET_COUNT]; // for debugging

    const bool use_textures = getMaterialType() != LLTerrainMaterials::Type::PBR;
    if (use_textures)
    {
        if (!texturesReady(true, true)) { return FALSE; }
    }
    else
    {
        if (!materialsReady(true, true)) { return FALSE; }
    }

	for (S32 i = 0; i < ASSET_COUNT; i++)
	{
		if (mRawImages[i].isNull())
		{
			// Read back a raw image for this discard level, if it exists
            LLViewerFetchedTexture* tex;
            LLViewerFetchedTexture* tex_emissive; // Can be null
            bool has_base_color_factor;
            bool has_emissive_factor;
            bool has_alpha;
            LLColor3 base_color_factor;
            LLColor3 emissive_factor;
            if (use_textures)
            {
                tex = mDetailTextures[i];
                tex_emissive = nullptr;
                has_base_color_factor = false;
                has_emissive_factor = false;
                has_alpha = false;
                llassert(tex);
            }
            else
            {
                tex = mDetailMaterials[i]->mBaseColorTexture;
                tex_emissive = mDetailMaterials[i]->mEmissiveTexture;
                base_color_factor = LLColor3(mDetailMaterials[i]->mBaseColor);
                // *HACK: Treat alpha as black
                base_color_factor *= (mDetailMaterials[i]->mBaseColor.mV[VW]);
                emissive_factor = mDetailMaterials[i]->mEmissiveColor;
                has_base_color_factor = (base_color_factor.mV[VX] != 1.f ||
                                         base_color_factor.mV[VY] != 1.f ||
                                         base_color_factor.mV[VZ] != 1.f);
                has_emissive_factor = (emissive_factor.mV[VX] != 1.f ||
                                       emissive_factor.mV[VY] != 1.f ||
                                       emissive_factor.mV[VZ] != 1.f);
                has_alpha = mDetailMaterials[i]->mAlphaMode != LLGLTFMaterial::ALPHA_MODE_OPAQUE;
            }

            if (!tex) { tex = LLViewerFetchedTexture::sWhiteImagep; }

            bool delete_raw_post = false;
            bool delete_raw_post_emissive = false;
            if (!prepare_raw_image(mRawImagesBaseColor[i], false, tex, delete_raw_post)) { return FALSE; }
            if (tex_emissive && !prepare_raw_image(mRawImagesEmissive[i], true, tex_emissive, delete_raw_post_emissive)) { return FALSE; }
            // tex_emissive can be null, and then will be ignored

            // In the simplest case, the minimap image is just the base color.
            // This will be replaced if we need to do any tinting/compositing.
            mRawImages[i] = mRawImagesBaseColor[i];

            // *TODO: This isn't quite right for PBR:
            // 1) It does not convert the color images from SRGB to linear
            // before mixing (which will always require copying the image).
            // 2) It mixes emissive and base color before mixing terrain
            // materials, but it should be the other way around
            // Long-term, we should consider a method that is more
            // maintainable. Shaders, perhaps? Bake shaders to textures?
            LLPointer<LLImageRaw> raw_emissive;
            if (tex_emissive)
            {
                raw_emissive = mRawImagesEmissive[i];
                if (has_emissive_factor ||
                    tex_emissive->getWidth(tex_emissive->getRawImageLevel()) != BASE_SIZE ||
                    tex_emissive->getHeight(tex_emissive->getRawImageLevel()) != BASE_SIZE ||
                    tex_emissive->getComponents() != 4)
                {
                    LLPointer<LLImageRaw> newraw_emissive = new LLImageRaw(BASE_SIZE, BASE_SIZE, 4);
                    // Copy RGB, leave alpha alone (set to opaque by default)
                    newraw_emissive->copy(mRawImagesEmissive[i]);
                    if (has_emissive_factor)
                    {
                        newraw_emissive->tint(emissive_factor);
                    }
                    raw_emissive = newraw_emissive;
                }
            }
			if (has_base_color_factor ||
                raw_emissive ||
                has_alpha ||
                tex->getWidth(tex->getRawImageLevel()) != BASE_SIZE ||
				tex->getHeight(tex->getRawImageLevel()) != BASE_SIZE ||
				tex->getComponents() != 3)
			{
				LLPointer<LLImageRaw> newraw = new LLImageRaw(BASE_SIZE, BASE_SIZE, 3);
                if (has_alpha)
                {
                    // Approximate the water underneath terrain alpha with solid water color
                    newraw->clear(
                        MAX_WATER_COLOR.mV[VX],
                        MAX_WATER_COLOR.mV[VY],
                        MAX_WATER_COLOR.mV[VZ],
                        255);
                }
				newraw->composite(mRawImagesBaseColor[i]);
                if (has_base_color_factor)
                {
                    newraw->tint(base_color_factor);
                }
                // Apply emissive texture
                if (raw_emissive)
                {
                    newraw->addEmissive(raw_emissive);
                }

				mRawImages[i] = newraw; // deletes old
			}

            if (delete_raw_post)
            {
                tex->destroyRawImage();
            }
            if (delete_raw_post_emissive)
            {
                tex_emissive->destroyRawImage();
            }

            // Remove intermediary image references
            mRawImagesBaseColor[i] = nullptr;
            mRawImagesEmissive[i] = nullptr;
		}
		st_data[i] = mRawImages[i]->getData();
		st_data_size[i] = mRawImages[i]->getDataSize();
	}

	///////////////////////////////////////
	//
	// Generate and clamp x/y bounding box.
	//
	//

	S32 x_begin, y_begin, x_end, y_end;
	x_begin = (S32)(x * mScaleInv);
	y_begin = (S32)(y * mScaleInv);
	x_end = ll_round( (x + width) * mScaleInv );
	y_end = ll_round( (y + width) * mScaleInv );

	if (x_end > mWidth)
	{
        llassert(false);
		x_end = mWidth;
	}
	if (y_end > mWidth)
	{
        llassert(false);
		y_end = mWidth;
	}


	///////////////////////////////////////////
	//
	// Generate target texture information, stride ratios.
	//
	//

	LLViewerTexture *texturep;
	U32 tex_width, tex_height, tex_comps;
	U32 tex_stride;
	F32 tex_x_scalef, tex_y_scalef;
	S32 tex_x_begin, tex_y_begin, tex_x_end, tex_y_end;
	F32 tex_x_ratiof, tex_y_ratiof;

	texturep = mSurfacep->getSTexture();
	tex_width = texturep->getWidth();
	tex_height = texturep->getHeight();
	tex_comps = texturep->getComponents();
	tex_stride = tex_width * tex_comps;

	U32 st_comps = 3;
	U32 st_width = BASE_SIZE;
	U32 st_height = BASE_SIZE;
	
	if (tex_comps != st_comps)
	{
        llassert(false);
		return false;
	}

	tex_x_scalef = (F32)tex_width / (F32)mWidth;
	tex_y_scalef = (F32)tex_height / (F32)mWidth;
	tex_x_begin = (S32)((F32)x_begin * tex_x_scalef);
	tex_y_begin = (S32)((F32)y_begin * tex_y_scalef);
	tex_x_end = (S32)((F32)x_end * tex_x_scalef);
	tex_y_end = (S32)((F32)y_end * tex_y_scalef);

	tex_x_ratiof = (F32)mWidth*mScale / (F32)tex_width;
	tex_y_ratiof = (F32)mWidth*mScale / (F32)tex_height;

	LLPointer<LLImageRaw> raw = new LLImageRaw(tex_width, tex_height, tex_comps);
	U8 *rawp = raw->getData();

	F32 st_x_stride, st_y_stride;
	st_x_stride = ((F32)st_width / (F32)mTexScaleX)*((F32)mWidth / (F32)tex_width);
	st_y_stride = ((F32)st_height / (F32)mTexScaleY)*((F32)mWidth / (F32)tex_height);

	llassert(st_x_stride > 0.f);
	llassert(st_y_stride > 0.f);
	////////////////////////////////
	//
	// Iterate through the target texture, striding through the
	// subtextures and interpolating appropriately.
	//
	//

	F32 sti, stj;
	S32 st_offset;
	sti = (tex_x_begin * st_x_stride) - st_width*(llfloor((tex_x_begin * st_x_stride)/st_width));
	stj = (tex_y_begin * st_y_stride) - st_height*(llfloor((tex_y_begin * st_y_stride)/st_height));

	st_offset = (llfloor(stj * st_width) + llfloor(sti)) * st_comps;
	for (S32 j = tex_y_begin; j < tex_y_end; j++)
	{
		U32 offset = j * tex_stride + tex_x_begin * tex_comps;
		sti = (tex_x_begin * st_x_stride) - st_width*((U32)(tex_x_begin * st_x_stride)/st_width);
		for (S32 i = tex_x_begin; i < tex_x_end; i++)
		{
			S32 tex0, tex1;
			F32 composition = getValueScaled(i*tex_x_ratiof, j*tex_y_ratiof);

			tex0 = llfloor( composition );
			tex0 = llclamp(tex0, 0, 3);
			composition -= tex0;
			tex1 = tex0 + 1;
			tex1 = llclamp(tex1, 0, 3);

			st_offset = (lltrunc(sti) + lltrunc(stj)*st_width) * st_comps;
			for (U32 k = 0; k < tex_comps; k++)
			{
				// Linearly interpolate based on composition.
				if (st_offset >= st_data_size[tex0] || st_offset >= st_data_size[tex1])
				{
					// SJB: This shouldn't be happening, but does... Rounding error?
					//LL_WARNS() << "offset 0 [" << tex0 << "] =" << st_offset << " >= size=" << st_data_size[tex0] << LL_ENDL;
					//LL_WARNS() << "offset 1 [" << tex1 << "] =" << st_offset << " >= size=" << st_data_size[tex1] << LL_ENDL;
				}
				else
				{
					F32 a = *(st_data[tex0] + st_offset);
					F32 b = *(st_data[tex1] + st_offset);
					rawp[ offset ] = (U8)lltrunc( a + composition * (b - a) );
				}
				offset++;
				st_offset++;
			}

			sti += st_x_stride;
			if (sti >= st_width)
			{
				sti -= st_width;
			}
		}

		stj += st_y_stride;
		if (stj >= st_height)
		{
			stj -= st_height;
		}
	}

	if (!texturep->hasGLTexture())
	{
		texturep->createGLTexture(0, raw);
	}
	texturep->setSubImage(raw, tex_x_begin, tex_y_begin, tex_x_end - tex_x_begin, tex_y_end - tex_y_begin);

    // Un-boost detail textures (will get re-boosted if rendering in high detail)
    for (S32 i = 0; i < ASSET_COUNT; i++)
    {
        unboost_minimap_texture(mDetailTextures[i]);
    }

    // Un-boost textures for each detail material (will get re-boosted if rendering in high detail)
    for (S32 i = 0; i < ASSET_COUNT; i++)
    {
        unboost_minimap_material(mDetailMaterials[i]);
    }
	
	return true;
}

F32 LLVLComposition::getStartHeight(S32 corner)
{
	return mStartHeight[corner];
}

void LLVLComposition::setDetailAssetID(S32 asset, const LLUUID& id)
{
	if (id.isNull())
	{
        return;
    }
    LLTerrainMaterials::setDetailAssetID(asset, id);
	mRawImages[asset] = NULL;
	mRawImagesBaseColor[asset] = NULL;
	mRawImagesEmissive[asset] = NULL;
}

void LLVLComposition::setStartHeight(S32 corner, const F32 start_height)
{
	mStartHeight[corner] = start_height;
}

F32 LLVLComposition::getHeightRange(S32 corner)
{
	return mHeightRange[corner];
}

void LLVLComposition::setHeightRange(S32 corner, const F32 range)
{
	mHeightRange[corner] = range;
}