gltfpack: Switch to EXT_meshopt_compression extension

We now produce files encoded with EXT_ extension variant, and
string-like enums for compression mode/filter instead of integer enums.

gltf/README.md

@@ -22,7 +22,7 @@ gltfpack substantially changes the glTF data by optimizing the meshes for vertex
 
 By default gltfpack outputs regular `.glb`/`.gltf` files that have been optimized for GPU consumption using various cache optimizers and quantization. These files can be loaded by GLTF loaders that support `KHR_mesh_quantization` extension such as [three.js](https://threejs.org/) (r111+) and [Babylon.js](https://www.babylonjs.com/) (4.1+).
 
-When using `-c` option, gltfpack outputs compressed `.glb`/`.gltf` files that use meshoptimizer codecs to reduce the download size further. Loading these files requires extending GLTF loaders with support for `MESHOPT_compression` extension; [demo/GLTFLoader.js](https://github.com/zeux/meshoptimizer/blob/master/demo/GLTFLoader.js) contains a custom version of three.js loader that can be used to load them.
+When using `-c` option, gltfpack outputs compressed `.glb`/`.gltf` files that use meshoptimizer codecs to reduce the download size further. Loading these files requires extending GLTF loaders with support for `EXT_meshopt_compression` extension; [demo/GLTFLoader.js](https://github.com/zeux/meshoptimizer/blob/master/demo/GLTFLoader.js) contains a custom version of three.js loader that can be used to load them.
 
 For better compression, you can use `-cc` option which applies additional compression; additionally make sure that your content delivery method is configured to use deflate (gzip) - meshoptimizer codecs are designed to produce output that can be compressed further with general purpose compressors.
 

gltf/gltfpack.cpp

@@ -563,7 +563,7 @@ static void process(cgltf_data* data, const char* input_path, const char* output
 
 	const ExtensionInfo extensions[] = {
 	    {"KHR_mesh_quantization", settings.quantize, true},
-	    {"MESHOPT_compression", settings.compress, !settings.fallback},
+	    {"EXT_meshopt_compression", settings.compress, !settings.fallback},
 	    {"KHR_texture_transform", settings.quantize && !json_textures.empty(), false},
 	    {"KHR_materials_pbrSpecularGlossiness", ext_pbr_specular_glossiness, false},
 	    {"KHR_materials_clearcoat", ext_clearcoat, false},
@@ -669,7 +669,7 @@ static std::string getBufferSpec(const char* bin_path, size_t bin_size, const ch
 		append(json, "\"byteLength\":");
 		append(json, fallback_size);
 		append(json, ",\"extensions\":{");
-		append(json, "\"MESHOPT_compression\":{");
+		append(json, "\"EXT_meshopt_compression\":{");
 		append(json, "\"fallback\":true");
 		append(json, "}}");
 		append(json, "}");

gltf/parsegltf.cpp

@@ -478,7 +478,7 @@ cgltf_data* parseGltf(const char* path, std::vector<Mesh>& meshes, std::vector<A
 		*error = getError(result, data);
 	else if (requiresExtension(data, "KHR_draco_mesh_compression"))
 		*error = "file requires Draco mesh compression support";
-	else if (requiresExtension(data, "MESHOPT_compression"))
+	else if (requiresExtension(data, "EXT_meshopt_compression"))
 		*error = "file has already been compressed using gltfpack";
 	else if (needsDummyBuffers(data))
 		*error = "buffer has no data";

gltf/write.cpp

@@ -104,6 +104,63 @@ static const char* lightType(cgltf_light_type type)
 	}
 }
 
+static const char* alphaMode(cgltf_alpha_mode mode)
+{
+	switch (mode)
+	{
+	case cgltf_alpha_mode_opaque:
+		return "OPAQUE";
+
+	case cgltf_alpha_mode_mask:
+		return "MASK";
+
+	case cgltf_alpha_mode_blend:
+		return "BLEND";
+
+	default:
+		return "";
+	}
+}
+
+static const char* compressionMode(BufferView::Compression mode)
+{
+	switch (mode)
+	{
+	case BufferView::Compression_Attribute:
+		return "ATTRIBUTES";
+
+	case BufferView::Compression_Index:
+		return "TRIANGLES";
+
+	case BufferView::Compression_IndexSequence:
+		return "INDICES";
+
+	default:
+		return "";
+	}
+}
+
+static const char* compressionFilter(StreamFormat::Filter filter)
+{
+	switch (filter)
+	{
+	case StreamFormat::Filter_None:
+		return "NONE";
+
+	case StreamFormat::Filter_Oct:
+		return "OCTAHEDRAL";
+
+	case StreamFormat::Filter_Quat:
+		return "QUATERNION";
+
+	case StreamFormat::Filter_Exp:
+		return "EXPONENTIAL";
+
+	default:
+		return "";
+	}
+}
+
 static void writeTextureInfo(std::string& json, const cgltf_data* data, const cgltf_texture_view& view, const QuantizationTexture* qt)
 {
 	assert(view.texture);
@@ -337,8 +394,9 @@ void writeMaterial(std::string& json, const cgltf_data* data, const cgltf_materi
 	if (material.alpha_mode != cgltf_alpha_mode_opaque)
 	{
 		comma(json);
-		append(json, "\"alphaMode\":");
-		append(json, (material.alpha_mode == cgltf_alpha_mode_blend) ? "\"BLEND\"" : "\"MASK\"");
+		append(json, "\"alphaMode\":\"");
+		append(json, alphaMode(material.alpha_mode));
+		append(json, "\"");
 	}
 
 	if (material.alpha_cutoff != 0.5f)
@@ -404,7 +462,7 @@ void writeBufferView(std::string& json, BufferView::Kind kind, StreamFormat::Fil
 
 	// when compression is enabled, we store uncompressed data in buffer 1 and compressed data in buffer 0
 	// when compression is disabled, we store uncompressed data in buffer 0
-	size_t buffer = compression >= 0 ? 1 : 0;
+	size_t buffer = compression != BufferView::Compression_None ? 1 : 0;
 
 	append(json, "{\"buffer\":");
 	append(json, buffer);
@@ -425,20 +483,22 @@ void writeBufferView(std::string& json, BufferView::Kind kind, StreamFormat::Fil
 	if (compression != BufferView::Compression_None)
 	{
 		append(json, ",\"extensions\":{");
-		append(json, "\"MESHOPT_compression\":{");
+		append(json, "\"EXT_meshopt_compression\":{");
 		append(json, "\"buffer\":0");
 		append(json, ",\"byteOffset\":");
 		append(json, size_t(compressed_offset));
 		append(json, ",\"byteLength\":");
 		append(json, size_t(compressed_size));
 		append(json, ",\"byteStride\":");
 		append(json, stride);
-		append(json, ",\"mode\":");
-		append(json, size_t(compression));
+		append(json, ",\"mode\":\"");
+		append(json, compressionMode(compression));
+		append(json, "\"");
 		if (filter != StreamFormat::Filter_None)
 		{
-			append(json, ",\"filter\":");
-			append(json, size_t(filter));
+			append(json, ",\"filter\":\"");
+			append(json, compressionFilter(filter));
+			append(json, "\"");
 		}
 		append(json, ",\"count\":");
 		append(json, count);