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