#1654 generate normals and tangents according to gltf specification (#1662)

* Disable unloading of objects in background. 
* Add unlit GLTF shader variant

3 files changed, 323 insertions, 54 deletions

diff --git a/indra/newview/gltf/buffer_util.h b/indra/newview/gltf/buffer_util.h
index 548d4ec5d6..bd43f60d19 100644
--- a/indra/newview/gltf/buffer_util.h
+++ b/indra/newview/gltf/buffer_util.h
@@ -171,6 +171,16 @@ namespace LL
         }
 
         template<>
+        inline void copyVec4<U16, U64>(U16* src, U64& dst)
+        {
+            U16* data = (U16*)&dst;
+            data[0] = src[0];
+            data[1] = src[1];
+            data[2] = src[2];
+            data[3] = src[3];
+        }
+
+        template<>
         inline void copyVec4<U16, LLColor4U>(U16* src, LLColor4U& dst)
         {
             dst.set(src[0], src[1], src[2], src[3]);
diff --git a/indra/newview/gltf/primitive.cpp b/indra/newview/gltf/primitive.cpp
index 886b8f79c9..8d9880951b 100644
--- a/indra/newview/gltf/primitive.cpp
+++ b/indra/newview/gltf/primitive.cpp
@@ -30,9 +30,204 @@
 #include "buffer_util.h"
 #include "../llviewershadermgr.h"
 
+#include "mikktspace/mikktspace.hh"
+
+#include "meshoptimizer/meshoptimizer.h"
+
+
 using namespace LL::GLTF;
 using namespace boost::json;
 
+
+// Mesh data useful for Mikktspace tangent generation (and flat normal generation)
+struct MikktMesh
+{
+    std::vector<LLVector3> p;
+    std::vector<LLVector3> n;
+    std::vector<LLVector2> tc;
+    std::vector<LLVector4> w;
+    std::vector<LLVector4> t;
+    std::vector<LLColor4U> c;
+    std::vector<U64> j;
+
+    // initialize from src primitive and make an unrolled triangle list
+    // returns false if the Primitive cannot be converted to a triangle list
+    bool copy(const Primitive* prim)
+    {
+        bool indexed = !prim->mIndexArray.empty();
+        U32 vert_count = indexed ? prim->mIndexArray.size() : prim->mPositions.size();
+
+        if (prim->mMode != Primitive::Mode::TRIANGLES)
+        {
+            LL_WARNS("GLTF") << "Unsupported primitive mode for conversion to triangles: " << (S32) prim->mMode << LL_ENDL;
+            return false;
+        }
+
+        p.resize(vert_count);
+        n.resize(vert_count);
+        tc.resize(vert_count);
+        c.resize(vert_count);
+
+        bool has_normals = !prim->mNormals.empty();
+        if (has_normals)
+        {
+            n.resize(vert_count);
+        }
+        bool has_tangents = !prim->mTangents.empty();
+        if (has_tangents)
+        {
+            t.resize(vert_count);
+        }
+        bool rigged = !prim->mWeights.empty();
+        if (rigged)
+        {
+            w.resize(vert_count);
+            j.resize(vert_count);
+        }
+
+        for (int i = 0; i < vert_count; ++i)
+        {
+            U32 idx = indexed ? prim->mIndexArray[i] : i;
+
+            p[i].set(prim->mPositions[idx].getF32ptr());
+            tc[i].set(prim->mTexCoords[idx]);
+            c[i] = prim->mColors[idx];
+
+            if (has_normals)
+            {
+                n[i].set(prim->mNormals[idx].getF32ptr());
+            }
+
+            if (rigged)
+            {
+                w[i].set(prim->mWeights[idx].getF32ptr());
+                j[i] = prim->mJoints[idx];
+            }
+        }
+
+        return true;
+    }
+
+    void genNormals()
+    {
+        U32 tri_count = p.size() / 3;
+        for (U32 i = 0; i < tri_count; ++i)
+        {
+            LLVector3 v0 = p[i * 3];
+            LLVector3 v1 = p[i * 3 + 1];
+            LLVector3 v2 = p[i * 3 + 2];
+
+            LLVector3 normal = (v1 - v0) % (v2 - v0);
+            normal.normalize();
+
+            n[i * 3] = normal;
+            n[i * 3 + 1] = normal;
+            n[i * 3 + 2] = normal;
+        }
+    }
+
+    void genTangents()
+    {
+        t.resize(p.size());
+        mikk::Mikktspace ctx(*this);
+        ctx.genTangSpace();
+    }
+
+    // write to target primitive as an indexed triangle list
+    // Only modifies runtime data, does not modify the original GLTF data
+    void write(Primitive* prim) const
+    {
+        //re-weld
+        meshopt_Stream mos[] =
+        {
+            { &p[0], sizeof(LLVector3), sizeof(LLVector3) },
+            { &n[0], sizeof(LLVector3), sizeof(LLVector3) },
+            { &t[0], sizeof(LLVector4), sizeof(LLVector4) },
+            { &tc[0], sizeof(LLVector2), sizeof(LLVector2) },
+            { &c[0], sizeof(LLColor4U), sizeof(LLColor4U) },
+            { w.empty() ? nullptr : &w[0], sizeof(LLVector4), sizeof(LLVector4) },
+            { j.empty() ? nullptr : &j[0], sizeof(U64), sizeof(U64) }
+        };
+
+        std::vector<U32> remap;
+        remap.resize(p.size());
+
+        U32 stream_count = w.empty() ? 5 : 7;
+
+        size_t vert_count = meshopt_generateVertexRemapMulti(&remap[0], nullptr, p.size(), p.size(), mos, stream_count);
+
+        prim->mTexCoords.resize(vert_count);
+        prim->mNormals.resize(vert_count);
+        prim->mTangents.resize(vert_count);
+        prim->mPositions.resize(vert_count);
+        prim->mColors.resize(vert_count);
+        if (!w.empty())
+        {
+            prim->mWeights.resize(vert_count);
+            prim->mJoints.resize(vert_count);
+        }
+        
+        prim->mIndexArray.resize(remap.size());
+
+        for (int i = 0; i < remap.size(); ++i)
+        {
+            U32 src_idx = i;
+            U32 dst_idx = remap[i];
+
+            prim->mIndexArray[i] = dst_idx;
+
+            prim->mPositions[dst_idx].load3(p[src_idx].mV);
+            prim->mNormals[dst_idx].load3(n[src_idx].mV);
+            prim->mTexCoords[dst_idx] = tc[src_idx];
+            prim->mTangents[dst_idx].loadua(t[src_idx].mV);
+            prim->mColors[dst_idx] = c[src_idx];
+
+            if (!w.empty())
+            {
+                prim->mWeights[dst_idx].loadua(w[src_idx].mV);
+                prim->mJoints[dst_idx] = j[src_idx];
+            }
+        }
+
+        prim->mGLMode = LLRender::TRIANGLES;
+    }
+
+    uint32_t GetNumFaces()
+    {
+        return uint32_t(p.size()/3);
+    }
+
+    uint32_t GetNumVerticesOfFace(const uint32_t face_num)
+    {
+        return 3;
+    }
+
+    mikk::float3 GetPosition(const uint32_t face_num, const uint32_t vert_num)
+    {
+        F32* v = p[face_num * 3 + vert_num].mV;
+        return mikk::float3(v);
+    }
+
+    mikk::float3 GetTexCoord(const uint32_t face_num, const uint32_t vert_num)
+    {
+        F32* uv = tc[face_num * 3 + vert_num].mV;
+        return mikk::float3(uv[0], uv[1], 1.0f);
+    }
+
+    mikk::float3 GetNormal(const uint32_t face_num, const uint32_t vert_num)
+    {
+        F32* normal = n[face_num * 3 + vert_num].mV;
+        return mikk::float3(normal);
+    }
+
+    void SetTangentSpace(const uint32_t face_num, const uint32_t vert_num, mikk::float3 T, bool orientation)
+    {
+        S32 i = face_num * 3 + vert_num;
+        t[i].set(T.x, T.y, T.z, orientation ? 1.0f : -1.0f);
+    }
+};
+
+
 bool Primitive::prep(Asset& asset)
 {
     // allocate vertex buffer
@@ -94,26 +289,12 @@ bool Primitive::prep(Asset& asset)
         }
     }
 
-    U32 mask = ATTRIBUTE_MASK;
+    U32 mask = LLVertexBuffer::MAP_VERTEX;
 
     if (!mWeights.empty())
     {
         mask |= LLVertexBuffer::MAP_WEIGHT4;
-    }
-
-    if (LLGLSLShader::sCurBoundShaderPtr == nullptr)
-    { // make sure a shader is bound to satisfy mVertexBuffer->setBuffer
-        gDebugProgram.bind();
-    }
-    mVertexBuffer = new LLVertexBuffer(mask);
-    mVertexBuffer->allocateBuffer(mPositions.size(), mIndexArray.size()*2); // double the size of the index buffer for 32-bit indices
-
-    mVertexBuffer->setBuffer();
-    mVertexBuffer->setPositionData(mPositions.data());
-
-    if (!mIndexArray.empty())
-    {
-        mVertexBuffer->setIndexData(mIndexArray.data());
+        mask |= LLVertexBuffer::MAP_JOINT;
     }
 
     if (mTexCoords.empty())
@@ -121,23 +302,17 @@ bool Primitive::prep(Asset& asset)
         mTexCoords.resize(mPositions.size());
     }
 
-    // flip texcoord y, upload, then flip back (keep the off-spec data in vram only)
-    for (auto& tc : mTexCoords)
-    {
-        tc[1] = 1.f - tc[1];
-    }
-    mVertexBuffer->setTexCoordData(mTexCoords.data());
-
-    for (auto& tc : mTexCoords)
-    {
-        tc[1] = 1.f - tc[1];
-    }
+    // TODO: support more than one texcoord set (or no texcoords)
+    mask |= LLVertexBuffer::MAP_TEXCOORD0;
 
     if (mColors.empty())
     {
         mColors.resize(mPositions.size(), LLColor4U::white);
     }
 
+    // TODO: support colorless vertex buffers
+    mask |= LLVertexBuffer::MAP_COLOR;
+
     // bake material basecolor into color array
     if (mMaterial != INVALID_INDEX)
     {
@@ -149,44 +324,131 @@ bool Primitive::prep(Asset& asset)
         }
     }
 
-    mVertexBuffer->setColorData(mColors.data());
+    mShaderVariant = 0;
 
     if (mNormals.empty())
     {
-        mNormals.resize(mPositions.size(), LLVector4a(0, 0, 1, 0));
+        mTangents.clear();
+
+        if (mMode == Mode::POINTS || mMode == Mode::LINES || mMode == Mode::LINE_LOOP || mMode == Mode::LINE_STRIP)
+        { //no normals and no surfaces, this primitive is unlit
+            mTangents.clear();
+            mShaderVariant |= LLGLSLShader::GLTFVariant::UNLIT;
+        }
+        else
+        {
+            // unroll into non-indexed array of flat shaded triangles
+            MikktMesh data;
+            if (!data.copy(this))
+            {
+                return false;
+            }
+
+            data.genNormals();
+            data.genTangents();
+            data.write(this);
+        }
+    }
+
+    bool unlit = (mShaderVariant & LLGLSLShader::GLTFVariant::UNLIT) != 0;
+
+    if (mTangents.empty() && !unlit)
+    { // NOTE: must be done last because tangent generation rewrites the other arrays
+        // adapted from usage of Mikktspace in llvolume.cpp
+        if (mMode == Mode::POINTS || mMode == Mode::LINES || mMode == Mode::LINE_LOOP || mMode == Mode::LINE_STRIP)
+        {
+            // for points and lines, just make sure tangent is perpendicular to normal
+            mTangents.resize(mNormals.size());
+            LLVector4a up(0.f, 0.f, 1.f, 0.f);
+            LLVector4a left(1.f, 0.f, 0.f, 0.f);
+            for (U32 i = 0; i < mNormals.size(); ++i)
+            {
+                if (fabsf(mNormals[i].getF32ptr()[2]) < 0.999f)
+                {
+                    mTangents[i] = up.cross3(mNormals[i]);
+                }
+                else
+                {
+                    mTangents[i] = left.cross3(mNormals[i]);
+                }
+
+                mTangents[i].getF32ptr()[3] = 1.f;
+            }
+        }
+        else
+        {
+            MikktMesh data;
+            if (!data.copy(this))
+            {
+                return false;
+            }
+
+            data.genTangents();
+            data.write(this);
+        }
     }
 
-    mVertexBuffer->setNormalData(mNormals.data());
 
-    if (mTangents.empty())
+    if (!unlit)
     {
-        // TODO: generate tangents if needed
-        mTangents.resize(mPositions.size(), LLVector4a(1, 0, 0, 1));
+        mask |= LLVertexBuffer::MAP_NORMAL;
+        mask |= LLVertexBuffer::MAP_TANGENT;
+    }
+
+    if (LLGLSLShader::sCurBoundShaderPtr == nullptr)
+    { // make sure a shader is bound to satisfy mVertexBuffer->setBuffer
+        gDebugProgram.bind();
     }
 
-    mVertexBuffer->setTangentData(mTangents.data());
+    mVertexBuffer = new LLVertexBuffer(mask);
+    mVertexBuffer->allocateBuffer(mPositions.size(), mIndexArray.size() * 2); // double the size of the index buffer for 32-bit indices
+
+    mVertexBuffer->setBuffer();
+    mVertexBuffer->setPositionData(mPositions.data());
+    mVertexBuffer->setColorData(mColors.data());
+
+    if (!mNormals.empty())
+    {
+        mVertexBuffer->setNormalData(mNormals.data());
+    }
+    if (!mTangents.empty())
+    {
+        mVertexBuffer->setTangentData(mTangents.data());
+    }
 
     if (!mWeights.empty())
     {
-        std::vector<LLVector4a> weight_data;
-        weight_data.resize(mWeights.size());
+        mShaderVariant |= LLGLSLShader::GLTFVariant::RIGGED;
+        mVertexBuffer->setWeight4Data(mWeights.data());
+        mVertexBuffer->setJointData(mJoints.data());
+    }
 
-        F32 max_weight = 1.f - FLT_EPSILON*100.f;
-        LLVector4a maxw(max_weight, max_weight, max_weight, max_weight);
-        for (U32 i = 0; i < mWeights.size(); ++i)
-        {
-            LLVector4a& w = weight_data[i];
-            w.setMin(mWeights[i], maxw);
-            w.add(mJoints[i]);
-        };
+    // flip texcoord y, upload, then flip back (keep the off-spec data in vram only)
+    for (auto& tc : mTexCoords)
+    {
+        tc[1] = 1.f - tc[1];
+    }
+    mVertexBuffer->setTexCoordData(mTexCoords.data());
+    for (auto& tc : mTexCoords)
+    {
+        tc[1] = 1.f - tc[1];
+    }
 
-        mVertexBuffer->setWeight4Data(weight_data.data());
+    if (!mIndexArray.empty())
+    {
+        mVertexBuffer->setIndexData(mIndexArray.data());
     }
 
     createOctree();
 
     mVertexBuffer->unbind();
 
+    Material& material = asset.mMaterials[mMaterial];
+    if (material.mAlphaMode == Material::AlphaMode::BLEND)
+    {
+        mShaderVariant |= LLGLSLShader::GLTFVariant::ALPHA_BLEND;
+    }
+
     return true;
 }
 
diff --git a/indra/newview/gltf/primitive.h b/indra/newview/gltf/primitive.h
index 9914ff3b08..f9d7c63c65 100644
--- a/indra/newview/gltf/primitive.h
+++ b/indra/newview/gltf/primitive.h
@@ -38,13 +38,6 @@ namespace LL
         using Value = boost::json::value;
         class Asset;
 
-        constexpr U32 ATTRIBUTE_MASK =
-            LLVertexBuffer::MAP_VERTEX |
-            LLVertexBuffer::MAP_NORMAL |
-            LLVertexBuffer::MAP_TEXCOORD0 |
-            LLVertexBuffer::MAP_TANGENT |
-            LLVertexBuffer::MAP_COLOR;
-
         class Primitive
         {
         public:
@@ -64,12 +57,12 @@ namespace LL
             // GPU copy of mesh data
             LLPointer<LLVertexBuffer> mVertexBuffer;
 
-            // CPU copy of mesh data
+            // CPU copy of mesh data, keep these as LLVector types for compatibility with raycasting code
             std::vector<LLVector2> mTexCoords;
             std::vector<LLVector4a> mNormals;
             std::vector<LLVector4a> mTangents;
             std::vector<LLVector4a> mPositions;
-            std::vector<LLVector4a> mJoints;
+            std::vector<U64> mJoints;
             std::vector<LLVector4a> mWeights;
             std::vector<LLColor4U> mColors;
             std::vector<U32> mIndexArray;
@@ -82,6 +75,10 @@ namespace LL
             Mode mMode = Mode::TRIANGLES; // default to triangles
             LLRender::eGeomModes mGLMode = LLRender::TRIANGLES; // for use with LLRender
             S32 mIndices = -1;
+
+            // shader variant according to LLGLSLShader::GLTFVariant flags
+            U8 mShaderVariant = 0;
+
             std::unordered_map<std::string, S32> mAttributes;
 
             // create octree based on vertex buffer