godot/thirdparty/meshoptimizer/vcacheanalyzer.cpp

// This file is part of meshoptimizer library; see meshoptimizer.h for version/license details
#include "meshoptimizer.h"

#include <assert.h>
#include <string.h>

meshopt_VertexCacheStatistics meshopt_analyzeVertexCache(const unsigned int* indices, size_t index_count, size_t vertex_count, unsigned int cache_size, unsigned int warp_size, unsigned int primgroup_size)
{
	assert(index_count % 3 == 0);
	assert(cache_size >= 3);
	assert(warp_size == 0 || warp_size >= 3);

	meshopt_Allocator allocator;

	meshopt_VertexCacheStatistics result = {};

	unsigned int warp_offset = 0;
	unsigned int primgroup_offset = 0;

	unsigned int* cache_timestamps = allocator.allocate<unsigned int>(vertex_count);
	memset(cache_timestamps, 0, vertex_count * sizeof(unsigned int));

	unsigned int timestamp = cache_size + 1;

	for (size_t i = 0; i < index_count; i += 3)
	{
		unsigned int a = indices[i + 0], b = indices[i + 1], c = indices[i + 2];
		assert(a < vertex_count && b < vertex_count && c < vertex_count);

		bool ac = (timestamp - cache_timestamps[a]) > cache_size;
		bool bc = (timestamp - cache_timestamps[b]) > cache_size;
		bool cc = (timestamp - cache_timestamps[c]) > cache_size;

		// flush cache if triangle doesn't fit into warp or into the primitive buffer
		if ((primgroup_size && primgroup_offset == primgroup_size) || (warp_size && warp_offset + ac + bc + cc > warp_size))
		{
			result.warps_executed += warp_offset > 0;

			warp_offset = 0;
			primgroup_offset = 0;

			// reset cache
			timestamp += cache_size + 1;
		}

		// update cache and add vertices to warp
		for (int j = 0; j < 3; ++j)
		{
			unsigned int index = indices[i + j];

			if (timestamp - cache_timestamps[index] > cache_size)
			{
				cache_timestamps[index] = timestamp++;
				result.vertices_transformed++;
				warp_offset++;
			}
		}

		primgroup_offset++;
	}

	size_t unique_vertex_count = 0;

	for (size_t i = 0; i < vertex_count; ++i)
		unique_vertex_count += cache_timestamps[i] > 0;

	result.warps_executed += warp_offset > 0;

	result.acmr = index_count == 0 ? 0 : float(result.vertices_transformed) / float(index_count / 3);
	result.atvr = unique_vertex_count == 0 ? 0 : float(result.vertices_transformed) / float(unique_vertex_count);

	return result;
}