59 lines
1.7 KiB
C++
59 lines
1.7 KiB
C++
// This file is part of meshoptimizer library; see meshoptimizer.h for version/license details
|
|
#include "meshoptimizer.h"
|
|
|
|
#include <assert.h>
|
|
#include <string.h>
|
|
|
|
meshopt_VertexFetchStatistics meshopt_analyzeVertexFetch(const unsigned int* indices, size_t index_count, size_t vertex_count, size_t vertex_size)
|
|
{
|
|
assert(index_count % 3 == 0);
|
|
assert(vertex_size > 0 && vertex_size <= 256);
|
|
|
|
meshopt_Allocator allocator;
|
|
|
|
meshopt_VertexFetchStatistics result = {};
|
|
|
|
unsigned char* vertex_visited = allocator.allocate<unsigned char>(vertex_count);
|
|
memset(vertex_visited, 0, vertex_count);
|
|
|
|
const size_t kCacheLine = 64;
|
|
const size_t kCacheSize = 128 * 1024;
|
|
|
|
// simple direct mapped cache; on typical mesh data this is close to 4-way cache, and this model is a gross approximation anyway
|
|
size_t cache[kCacheSize / kCacheLine] = {};
|
|
|
|
for (size_t i = 0; i < index_count; ++i)
|
|
{
|
|
unsigned int index = indices[i];
|
|
assert(index < vertex_count);
|
|
|
|
vertex_visited[index] = 1;
|
|
|
|
size_t start_address = index * vertex_size;
|
|
size_t end_address = start_address + vertex_size;
|
|
|
|
size_t start_tag = start_address / kCacheLine;
|
|
size_t end_tag = (end_address + kCacheLine - 1) / kCacheLine;
|
|
|
|
assert(start_tag < end_tag);
|
|
|
|
for (size_t tag = start_tag; tag < end_tag; ++tag)
|
|
{
|
|
size_t line = tag % (sizeof(cache) / sizeof(cache[0]));
|
|
|
|
// we store +1 since cache is filled with 0 by default
|
|
result.bytes_fetched += (cache[line] != tag + 1) * kCacheLine;
|
|
cache[line] = tag + 1;
|
|
}
|
|
}
|
|
|
|
size_t unique_vertex_count = 0;
|
|
|
|
for (size_t i = 0; i < vertex_count; ++i)
|
|
unique_vertex_count += vertex_visited[i];
|
|
|
|
result.overfetch = unique_vertex_count == 0 ? 0 : float(result.bytes_fetched) / float(unique_vertex_count * vertex_size);
|
|
|
|
return result;
|
|
}
|