Merge pull request #1041 from zeux/ml-optrot

 meshletutils: Restrict triangle rotation to optimizeMeshletLevel 1+

Author: zeux

README.md

@@ -429,7 +429,7 @@ Decoder is heavily optimized and can directly target write-combined memory; you
 
 > Applications that do most of the streaming decompression on the GPU can also decode meshlet data on the GPU if CPU decoding is inconvenient; an example [meshletdec.slang](./demo/meshletdec.slang) shader is provided for 32-bit output format, and can be easily adapted to other formats, including custom ones.
 
-Note that meshlet encoding assumes that the meshlet data was optimized; meshlets should be processed using `meshopt_optimizeMeshlet` before encoding. Additionally, vertex references should have a high degree of reference locality; this can be achieved by building meshlets from meshes optimized for vertex cache/fetch, or linearizing the vertex reference data and reordering the vertex buffer using `meshopt_optimizeVertexFetch`. For maximum compression, consider also using `meshopt_optimizeMeshletLevel` with level 3. Feeding unoptimized data into the encoder will result in poor compression ratios. Codec preserves the order of triangles, however it can rotate each triangle to improve compression ratio (which means the provoking vertex may change).
+Note that meshlet encoding assumes that the meshlet data was optimized; meshlets should be processed using `meshopt_optimizeMeshletLevel` with level 1 or higher (3 recommended for improved compression) before encoding. Additionally, vertex references should have a high degree of reference locality; this can be achieved by building meshlets from meshes optimized for vertex cache/fetch, or linearizing the vertex reference data and reordering the vertex buffer using `meshopt_optimizeVertexFetch`. Feeding unoptimized data into the encoder will result in poor compression ratios. Codec preserves the order of triangles, however it can rotate each triangle to improve compression ratio (which means the provoking vertex may change).
 
 Meshlets without vertex references are supported; passing `NULL` vertices and `0` vertex count during encoding and decoding will produce encoded meshlets with just triangle data. Note that parameters supplied during decoding must match those used during encoding; if a meshlet was encoded with vertex references, it must be decoded with the same number of vertex references.
 

demo/clusterlod.h

@@ -60,6 +60,7 @@ struct clodConfig
 
 	// should clodCluster::indices be optimized for locality; helps with rasterization performance and ray tracing performance in fast-build modes
 	bool optimize_clusters;
+	int optimize_clusters_level;
 };
 
 struct clodMesh
@@ -259,8 +260,13 @@ static std::vector<Cluster> clusterize(const clodConfig& config, const clodMesh&
 	{
 		const meshopt_Meshlet& meshlet = meshlets[i];
 
+#if MESHOPTIMIZER_VERSION < 1010
 		if (config.optimize_clusters)
 			meshopt_optimizeMeshlet(&meshlet_vertices[meshlet.vertex_offset], &meshlet_triangles[meshlet.triangle_offset], meshlet.triangle_count, meshlet.vertex_count);
+#else
+		if (config.optimize_clusters)
+			meshopt_optimizeMeshletLevel(&meshlet_vertices[meshlet.vertex_offset], meshlet.vertex_count, &meshlet_triangles[meshlet.triangle_offset], meshlet.triangle_count, config.optimize_clusters_level);
+#endif
 
 		clusters[i].vertices = meshlet.vertex_count;
 
@@ -522,6 +528,7 @@ clodConfig clodDefaultConfig(size_t max_triangles)
 	config.cluster_split_factor = 2.0f;
 
 	config.optimize_clusters = true;
+	config.optimize_clusters_level = 1;
 
 	config.simplify_ratio = 0.5f;
 	config.simplify_threshold = 0.85f;