godot/thirdparty/meshoptimizer/vcacheoptimizer.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>
// This work is based on:
// Tom Forsyth. Linear-Speed Vertex Cache Optimisation. 2006
// Pedro Sander, Diego Nehab and Joshua Barczak. Fast Triangle Reordering for Vertex Locality and Reduced Overdraw. 2007
namespace meshopt
{
const size_t kCacheSizeMax = 16;
const size_t kValenceMax = 8;
struct VertexScoreTable
{
float cache[1 + kCacheSizeMax];
float live[1 + kValenceMax];
};
// Tuned to minimize the ACMR of a GPU that has a cache profile similar to NVidia and AMD
static const VertexScoreTable kVertexScoreTable = {
{0.f, 0.779f, 0.791f, 0.789f, 0.981f, 0.843f, 0.726f, 0.847f, 0.882f, 0.867f, 0.799f, 0.642f, 0.613f, 0.600f, 0.568f, 0.372f, 0.234f},
{0.f, 0.995f, 0.713f, 0.450f, 0.404f, 0.059f, 0.005f, 0.147f, 0.006f},
};
// Tuned to minimize the encoded index buffer size
static const VertexScoreTable kVertexScoreTableStrip = {
{0.f, 1.000f, 1.000f, 1.000f, 0.453f, 0.561f, 0.490f, 0.459f, 0.179f, 0.526f, 0.000f, 0.227f, 0.184f, 0.490f, 0.112f, 0.050f, 0.131f},
{0.f, 0.956f, 0.786f, 0.577f, 0.558f, 0.618f, 0.549f, 0.499f, 0.489f},
};
struct TriangleAdjacency
{
unsigned int* counts;
unsigned int* offsets;
unsigned int* data;
};
static void buildTriangleAdjacency(TriangleAdjacency& adjacency, const unsigned int* indices, size_t index_count, size_t vertex_count, meshopt_Allocator& allocator)
{
size_t face_count = index_count / 3;
// allocate arrays
adjacency.counts = allocator.allocate<unsigned int>(vertex_count);
adjacency.offsets = allocator.allocate<unsigned int>(vertex_count);
adjacency.data = allocator.allocate<unsigned int>(index_count);
// fill triangle counts
memset(adjacency.counts, 0, vertex_count * sizeof(unsigned int));
for (size_t i = 0; i < index_count; ++i)
{
assert(indices[i] < vertex_count);
adjacency.counts[indices[i]]++;
}
// fill offset table
unsigned int offset = 0;
for (size_t i = 0; i < vertex_count; ++i)
{
adjacency.offsets[i] = offset;
offset += adjacency.counts[i];
}
assert(offset == index_count);
// fill triangle data
for (size_t i = 0; i < face_count; ++i)
{
unsigned int a = indices[i * 3 + 0], b = indices[i * 3 + 1], c = indices[i * 3 + 2];
adjacency.data[adjacency.offsets[a]++] = unsigned(i);
adjacency.data[adjacency.offsets[b]++] = unsigned(i);
adjacency.data[adjacency.offsets[c]++] = unsigned(i);
}
// fix offsets that have been disturbed by the previous pass
for (size_t i = 0; i < vertex_count; ++i)
{
assert(adjacency.offsets[i] >= adjacency.counts[i]);
adjacency.offsets[i] -= adjacency.counts[i];
}
}
static unsigned int getNextVertexDeadEnd(const unsigned int* dead_end, unsigned int& dead_end_top, unsigned int& input_cursor, const unsigned int* live_triangles, size_t vertex_count)
{
// check dead-end stack
while (dead_end_top)
{
unsigned int vertex = dead_end[--dead_end_top];
if (live_triangles[vertex] > 0)
return vertex;
}
// input order
while (input_cursor < vertex_count)
{
if (live_triangles[input_cursor] > 0)
return input_cursor;
++input_cursor;
}
return ~0u;
}
static unsigned int getNextVertexNeighbour(const unsigned int* next_candidates_begin, const unsigned int* next_candidates_end, const unsigned int* live_triangles, const unsigned int* cache_timestamps, unsigned int timestamp, unsigned int cache_size)
{
unsigned int best_candidate = ~0u;
int best_priority = -1;
for (const unsigned int* next_candidate = next_candidates_begin; next_candidate != next_candidates_end; ++next_candidate)
{
unsigned int vertex = *next_candidate;
// otherwise we don't need to process it
if (live_triangles[vertex] > 0)
{
int priority = 0;
// will it be in cache after fanning?
if (2 * live_triangles[vertex] + timestamp - cache_timestamps[vertex] <= cache_size)
{
priority = timestamp - cache_timestamps[vertex]; // position in cache
}
if (priority > best_priority)
{
best_candidate = vertex;
best_priority = priority;
}
}
}
return best_candidate;
}
static float vertexScore(const VertexScoreTable* table, int cache_position, unsigned int live_triangles)
{
assert(cache_position >= -1 && cache_position < int(kCacheSizeMax));
unsigned int live_triangles_clamped = live_triangles < kValenceMax ? live_triangles : kValenceMax;
return table->cache[1 + cache_position] + table->live[live_triangles_clamped];
}
static unsigned int getNextTriangleDeadEnd(unsigned int& input_cursor, const unsigned char* emitted_flags, size_t face_count)
{
// input order
while (input_cursor < face_count)
{
if (!emitted_flags[input_cursor])
return input_cursor;
++input_cursor;
}
return ~0u;
}
} // namespace meshopt
void meshopt_optimizeVertexCacheTable(unsigned int* destination, const unsigned int* indices, size_t index_count, size_t vertex_count, const meshopt::VertexScoreTable* table)
{
using namespace meshopt;
assert(index_count % 3 == 0);
meshopt_Allocator allocator;
// guard for empty meshes
if (index_count == 0 || vertex_count == 0)
return;
// support in-place optimization
if (destination == indices)
{
unsigned int* indices_copy = allocator.allocate<unsigned int>(index_count);
memcpy(indices_copy, indices, index_count * sizeof(unsigned int));
indices = indices_copy;
}
unsigned int cache_size = 16;
assert(cache_size <= kCacheSizeMax);
size_t face_count = index_count / 3;
// build adjacency information
TriangleAdjacency adjacency = {};
buildTriangleAdjacency(adjacency, indices, index_count, vertex_count, allocator);
// live triangle counts
unsigned int* live_triangles = allocator.allocate<unsigned int>(vertex_count);
memcpy(live_triangles, adjacency.counts, vertex_count * sizeof(unsigned int));
// emitted flags
unsigned char* emitted_flags = allocator.allocate<unsigned char>(face_count);
memset(emitted_flags, 0, face_count);
// compute initial vertex scores
float* vertex_scores = allocator.allocate<float>(vertex_count);
for (size_t i = 0; i < vertex_count; ++i)
vertex_scores[i] = vertexScore(table, -1, live_triangles[i]);
// compute triangle scores
float* triangle_scores = allocator.allocate<float>(face_count);
for (size_t i = 0; i < face_count; ++i)
{
unsigned int a = indices[i * 3 + 0];
unsigned int b = indices[i * 3 + 1];
unsigned int c = indices[i * 3 + 2];
triangle_scores[i] = vertex_scores[a] + vertex_scores[b] + vertex_scores[c];
}
unsigned int cache_holder[2 * (kCacheSizeMax + 3)];
unsigned int* cache = cache_holder;
unsigned int* cache_new = cache_holder + kCacheSizeMax + 3;
size_t cache_count = 0;
unsigned int current_triangle = 0;
unsigned int input_cursor = 1;
unsigned int output_triangle = 0;
while (current_triangle != ~0u)
{
assert(output_triangle < face_count);
unsigned int a = indices[current_triangle * 3 + 0];
unsigned int b = indices[current_triangle * 3 + 1];
unsigned int c = indices[current_triangle * 3 + 2];
// output indices
destination[output_triangle * 3 + 0] = a;
destination[output_triangle * 3 + 1] = b;
destination[output_triangle * 3 + 2] = c;
output_triangle++;
// update emitted flags
emitted_flags[current_triangle] = true;
triangle_scores[current_triangle] = 0;
// new triangle
size_t cache_write = 0;
cache_new[cache_write++] = a;
cache_new[cache_write++] = b;
cache_new[cache_write++] = c;
// old triangles
for (size_t i = 0; i < cache_count; ++i)
{
unsigned int index = cache[i];
if (index != a && index != b && index != c)
{
cache_new[cache_write++] = index;
}
}
unsigned int* cache_temp = cache;
cache = cache_new, cache_new = cache_temp;
cache_count = cache_write > cache_size ? cache_size : cache_write;
// update live triangle counts
live_triangles[a]--;
live_triangles[b]--;
live_triangles[c]--;
// remove emitted triangle from adjacency data
// this makes sure that we spend less time traversing these lists on subsequent iterations
for (size_t k = 0; k < 3; ++k)
{
unsigned int index = indices[current_triangle * 3 + k];
unsigned int* neighbours = &adjacency.data[0] + adjacency.offsets[index];
size_t neighbours_size = adjacency.counts[index];
for (size_t i = 0; i < neighbours_size; ++i)
{
unsigned int tri = neighbours[i];
if (tri == current_triangle)
{
neighbours[i] = neighbours[neighbours_size - 1];
adjacency.counts[index]--;
break;
}
}
}
unsigned int best_triangle = ~0u;
float best_score = 0;
// update cache positions, vertex scores and triangle scores, and find next best triangle
for (size_t i = 0; i < cache_write; ++i)
{
unsigned int index = cache[i];
int cache_position = i >= cache_size ? -1 : int(i);
// update vertex score
float score = vertexScore(table, cache_position, live_triangles[index]);
float score_diff = score - vertex_scores[index];
vertex_scores[index] = score;
// update scores of vertex triangles
const unsigned int* neighbours_begin = &adjacency.data[0] + adjacency.offsets[index];
const unsigned int* neighbours_end = neighbours_begin + adjacency.counts[index];
for (const unsigned int* it = neighbours_begin; it != neighbours_end; ++it)
{
unsigned int tri = *it;
assert(!emitted_flags[tri]);
float tri_score = triangle_scores[tri] + score_diff;
assert(tri_score > 0);
if (best_score < tri_score)
{
best_triangle = tri;
best_score = tri_score;
}
triangle_scores[tri] = tri_score;
}
}
// step through input triangles in order if we hit a dead-end
current_triangle = best_triangle;
if (current_triangle == ~0u)
{
current_triangle = getNextTriangleDeadEnd(input_cursor, &emitted_flags[0], face_count);
}
}
assert(input_cursor == face_count);
assert(output_triangle == face_count);
}
void meshopt_optimizeVertexCache(unsigned int* destination, const unsigned int* indices, size_t index_count, size_t vertex_count)
{
meshopt_optimizeVertexCacheTable(destination, indices, index_count, vertex_count, &meshopt::kVertexScoreTable);
}
void meshopt_optimizeVertexCacheStrip(unsigned int* destination, const unsigned int* indices, size_t index_count, size_t vertex_count)
{
meshopt_optimizeVertexCacheTable(destination, indices, index_count, vertex_count, &meshopt::kVertexScoreTableStrip);
}
void meshopt_optimizeVertexCacheFifo(unsigned int* destination, const unsigned int* indices, size_t index_count, size_t vertex_count, unsigned int cache_size)
{
using namespace meshopt;
assert(index_count % 3 == 0);
assert(cache_size >= 3);
meshopt_Allocator allocator;
// guard for empty meshes
if (index_count == 0 || vertex_count == 0)
return;
// support in-place optimization
if (destination == indices)
{
unsigned int* indices_copy = allocator.allocate<unsigned int>(index_count);
memcpy(indices_copy, indices, index_count * sizeof(unsigned int));
indices = indices_copy;
}
size_t face_count = index_count / 3;
// build adjacency information
TriangleAdjacency adjacency = {};
buildTriangleAdjacency(adjacency, indices, index_count, vertex_count, allocator);
// live triangle counts
unsigned int* live_triangles = allocator.allocate<unsigned int>(vertex_count);
memcpy(live_triangles, adjacency.counts, vertex_count * sizeof(unsigned int));
// cache time stamps
unsigned int* cache_timestamps = allocator.allocate<unsigned int>(vertex_count);
memset(cache_timestamps, 0, vertex_count * sizeof(unsigned int));
// dead-end stack
unsigned int* dead_end = allocator.allocate<unsigned int>(index_count);
unsigned int dead_end_top = 0;
// emitted flags
unsigned char* emitted_flags = allocator.allocate<unsigned char>(face_count);
memset(emitted_flags, 0, face_count);
unsigned int current_vertex = 0;
unsigned int timestamp = cache_size + 1;
unsigned int input_cursor = 1; // vertex to restart from in case of dead-end
unsigned int output_triangle = 0;
while (current_vertex != ~0u)
{
const unsigned int* next_candidates_begin = &dead_end[0] + dead_end_top;
// emit all vertex neighbours
const unsigned int* neighbours_begin = &adjacency.data[0] + adjacency.offsets[current_vertex];
const unsigned int* neighbours_end = neighbours_begin + adjacency.counts[current_vertex];
for (const unsigned int* it = neighbours_begin; it != neighbours_end; ++it)
{
unsigned int triangle = *it;
if (!emitted_flags[triangle])
{
unsigned int a = indices[triangle * 3 + 0], b = indices[triangle * 3 + 1], c = indices[triangle * 3 + 2];
// output indices
destination[output_triangle * 3 + 0] = a;
destination[output_triangle * 3 + 1] = b;
destination[output_triangle * 3 + 2] = c;
output_triangle++;
// update dead-end stack
dead_end[dead_end_top + 0] = a;
dead_end[dead_end_top + 1] = b;
dead_end[dead_end_top + 2] = c;
dead_end_top += 3;
// update live triangle counts
live_triangles[a]--;
live_triangles[b]--;
live_triangles[c]--;
// update cache info
// if vertex is not in cache, put it in cache
if (timestamp - cache_timestamps[a] > cache_size)
cache_timestamps[a] = timestamp++;
if (timestamp - cache_timestamps[b] > cache_size)
cache_timestamps[b] = timestamp++;
if (timestamp - cache_timestamps[c] > cache_size)
cache_timestamps[c] = timestamp++;
// update emitted flags
emitted_flags[triangle] = true;
}
}
// next candidates are the ones we pushed to dead-end stack just now
const unsigned int* next_candidates_end = &dead_end[0] + dead_end_top;
// get next vertex
current_vertex = getNextVertexNeighbour(next_candidates_begin, next_candidates_end, &live_triangles[0], &cache_timestamps[0], timestamp, cache_size);
if (current_vertex == ~0u)
{
current_vertex = getNextVertexDeadEnd(&dead_end[0], dead_end_top, input_cursor, &live_triangles[0], vertex_count);
}
}
assert(output_triangle == face_count);
}