Customisable Draco encoding options.

CMakeLists.txt

@@ -27,7 +27,7 @@ endif()
 # DRACO
 ExternalProject_Add(Draco
   GIT_REPOSITORY https://github.com/google/draco
-  GIT_TAG 1.2.5
+  GIT_TAG 1.3.1
   PREFIX draco
   INSTALL_DIR
   CMAKE_ARGS

src/Raw2Gltf.cpp

@@ -827,7 +827,7 @@ ModelData *Raw2Gltf(
                     && surfaceModel.GetVertexCount() > 65535);
 
             std::shared_ptr<PrimitiveData> primitive;
-            if (options.useDraco) {
+            if (options.draco.enabled) {
                 int triangleCount = surfaceModel.GetTriangleCount();
 
                 // initialize Draco mesh with vertex index information
@@ -943,17 +943,29 @@ ModelData *Raw2Gltf(
                     primitive->AddTarget(pAcc.get(), nAcc.get(), tAcc.get());
                 }
             }
-            if (options.useDraco) {
+            if (options.draco.enabled) {
                 // Set up the encoder.
                 draco::Encoder encoder;
 
-                // TODO: generalize / allow configuration
+                if (options.draco.compressionLevel != -1) {
-                encoder.SetSpeedOptions(5, 5);
+                    int dracoSpeed = 10 - options.draco.compressionLevel;
-                encoder.SetAttributeQuantization(draco::GeometryAttribute::POSITION, 14);
+                    encoder.SetSpeedOptions(dracoSpeed, dracoSpeed);
-                encoder.SetAttributeQuantization(draco::GeometryAttribute::TEX_COORD, 10);
+                }
-                encoder.SetAttributeQuantization(draco::GeometryAttribute::NORMAL, 10);
+                if (options.draco.quantBitsPosition != -1) {
-                encoder.SetAttributeQuantization(draco::GeometryAttribute::COLOR, 8);
+                    encoder.SetAttributeQuantization(draco::GeometryAttribute::POSITION, options.draco.quantBitsPosition);
-                encoder.SetAttributeQuantization(draco::GeometryAttribute::GENERIC, 8);
+                }
+                if (options.draco.quantBitsTexCoord != -1) {
+                    encoder.SetAttributeQuantization(draco::GeometryAttribute::TEX_COORD, options.draco.quantBitsTexCoord);
+                }
+                if (options.draco.quantBitsNormal != -1) {
+                    encoder.SetAttributeQuantization(draco::GeometryAttribute::NORMAL, options.draco.quantBitsNormal);
+                }
+                if (options.draco.quantBitsColor != -1) {
+                    encoder.SetAttributeQuantization(draco::GeometryAttribute::COLOR, options.draco.quantBitsColor);
+                }
+                if (options.draco.quantBitsGeneric != -1) {
+                    encoder.SetAttributeQuantization(draco::GeometryAttribute::GENERIC, options.draco.quantBitsGeneric);
+                }
 
                 draco::EncoderBuffer dracoBuffer;
                 draco::Status        status = encoder.EncodeMeshToBuffer(*primitive->dracoMesh, &dracoBuffer);
@@ -1070,7 +1082,7 @@ ModelData *Raw2Gltf(
         if (options.useKHRMatUnlit) {
             extensionsUsed.push_back(KHR_MATERIALS_CMN_UNLIT);
         }
-        if (options.useDraco) {
+        if (options.draco.enabled) {
             extensionsUsed.push_back(KHR_DRACO_MESH_COMPRESSION);
             extensionsRequired.push_back(KHR_DRACO_MESH_COMPRESSION);
         }

src/RawModel.h

@@ -46,8 +46,18 @@ struct GltfOptions
     bool outputBinary { false };
     /** If non-binary, whether to inline all resources, for a single (large) .glTF file. */
     bool embedResources { false };
-    /** Whether to use KHR_draco_mesh_compression to minimize static geometry size. */
+
-    bool useDraco { false };
+    /** Whether and how to use KHR_draco_mesh_compression to minimize static geometry size. */
+    struct {
+        bool enabled = false;
+        int compressionLevel = -1;
+        int quantBitsPosition = -1;
+        int quantBitsTexCoord = -1;
+        int quantBitsNormal = -1;
+        int quantBitsColor = -1;
+        int quantBitsGeneric = -1;
+    } draco;
+
     /** Whether to use KHR_materials_unlit to extend materials definitions. */
     bool useKHRMatUnlit { false };
     /** Whether to populate the pbrMetallicRoughness substruct in materials. */

src/main.cpp

@@ -63,7 +63,25 @@ int main(int argc, char *argv[])
                    cxxopts::value<std::vector<std::string>>())
                (
                    "d,draco", "Apply Draco mesh compression to geometries.",
-                   cxxopts::value<bool>(gltfOptions.useDraco))
+                   cxxopts::value<bool>(gltfOptions.draco.enabled))
+               (
+                   "draco-compression-level", "The compression level to tune Draco to, from 0 to 10. (default: 7)",
+                   cxxopts::value<int>(gltfOptions.draco.compressionLevel))
+               (
+                   "draco-bits-for-positions", "How many bits to quantize position to. (default: 14)",
+                   cxxopts::value<int>(gltfOptions.draco.quantBitsPosition))
+               (
+                   "draco-bits-for-uv", "How many bits to quantize UV coordinates to. (default: 10)",
+                   cxxopts::value<int>(gltfOptions.draco.quantBitsTexCoord))
+               (
+                   "draco-bits-for-normals", "How many bits to quantize normals to. (default: 10)",
+                   cxxopts::value<int>(gltfOptions.draco.quantBitsNormal))
+               (
+                   "draco-bits-for-colors", "How many bits to quantize color to. (default: 8)",
+                   cxxopts::value<int>(gltfOptions.draco.quantBitsColor))
+               (
+                   "draco-bits-for-other", "How many bits to quantize other vertex attributes to to. (default: 8)",
+                   cxxopts::value<int>(gltfOptions.draco.quantBitsGeneric))
                (
                    "compute-normals", "When to compute normals for vertices (never|broken|missing|always).",
                    cxxopts::value<std::vector<std::string>>())
@@ -125,6 +143,12 @@ int main(int argc, char *argv[])
         gltfOptions.usePBRMetRough = true;
     }
 
+    if (gltfOptions.draco.compressionLevel != -1 &&
+        (gltfOptions.draco.compressionLevel < 1 || gltfOptions.draco.compressionLevel > 10)) {
+        fmt::printf("Draco compression level must lie in [1, 10].\n");
+        return 0;
+    }
+
     if (options.count("flip-u") > 0) {
         texturesTransforms.emplace_back([](Vec2f uv) { return Vec2f(1.0f - uv[0], uv[1]); });
     }