godot/thirdparty/meshoptimizer/vfetchoptimizer.cpp

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// This file is part of meshoptimizer library; see meshoptimizer.h for version/license details
#include "meshoptimizer.h"
#include <assert.h>
#include <string.h>
size_t meshopt_optimizeVertexFetchRemap(unsigned int* destination, const unsigned int* indices, size_t index_count, size_t vertex_count)
{
assert(index_count % 3 == 0);
memset(destination, -1, vertex_count * sizeof(unsigned int));
unsigned int next_vertex = 0;
for (size_t i = 0; i < index_count; ++i)
{
unsigned int index = indices[i];
assert(index < vertex_count);
if (destination[index] == ~0u)
{
destination[index] = next_vertex++;
}
}
assert(next_vertex <= vertex_count);
return next_vertex;
}
size_t meshopt_optimizeVertexFetch(void* destination, unsigned int* indices, size_t index_count, const void* vertices, size_t vertex_count, size_t vertex_size)
{
assert(index_count % 3 == 0);
assert(vertex_size > 0 && vertex_size <= 256);
meshopt_Allocator allocator;
// support in-place optimization
if (destination == vertices)
{
unsigned char* vertices_copy = allocator.allocate<unsigned char>(vertex_count * vertex_size);
memcpy(vertices_copy, vertices, vertex_count * vertex_size);
vertices = vertices_copy;
}
// build vertex remap table
unsigned int* vertex_remap = allocator.allocate<unsigned int>(vertex_count);
memset(vertex_remap, -1, vertex_count * sizeof(unsigned int));
unsigned int next_vertex = 0;
for (size_t i = 0; i < index_count; ++i)
{
unsigned int index = indices[i];
assert(index < vertex_count);
unsigned int& remap = vertex_remap[index];
if (remap == ~0u) // vertex was not added to destination VB
{
// add vertex
memcpy(static_cast<unsigned char*>(destination) + next_vertex * vertex_size, static_cast<const unsigned char*>(vertices) + index * vertex_size, vertex_size);
remap = next_vertex++;
}
// modify indices in place
indices[i] = remap;
}
assert(next_vertex <= vertex_count);
return next_vertex;
}