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//-----------------------------------------------------------------------------
// This is an implementation of Tom Forsyth's "Linear-Speed Vertex Cache
// Optimization" algorithm as described here:
// https://tomforsyth1000.github.io/papers/fast_vert_cache_opt.html
//
// This code was authored and released into the public domain by
// Adrian Stone (stone@gameangst.com).
//
// THIS SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
// SHALL ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE FOR ANY DAMAGES OR OTHER
// LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
// IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//-----------------------------------------------------------------------------
// modified from original source to improve performance (especially in debug builds), memory allocations, etc.
#include "../Core/Utility.h"
#include <stdint.h>
#include <ASSERT.h>
#include <math.h>
#include <algorithm>
#include "IndexOptimizePostTransform.h"
namespace
{
// code for computing vertex score was taken, as much as possible
// directly from the original publication.
float ComputeVertexCacheScore(int cachePosition, size_t vertexCacheSize)
{
const float FindVertexScore_CacheDecayPower = 1.5f;
const float FindVertexScore_LastTriScore = 0.75f;
float score = 0.0f;
if ( cachePosition < 0 )
{
// Vertex is not in FIFO cache - no score.
}
else
{
if ( cachePosition < 3 )
{
// This vertex was used in the last triangle,
// so it has a fixed score, whichever of the three
// it's in. Otherwise, you can get very different
// answers depending on whether you add
// the triangle 1,2,3 or 3,1,2 - which is silly.
score = FindVertexScore_LastTriScore;
}
else
{
ASSERT ( cachePosition < int(vertexCacheSize) );
// Points for being high in the cache.
const float scaler = 1.0f / ( vertexCacheSize - 3 );
score = 1.0f - ( cachePosition - 3 ) * scaler;
score = powf ( score, FindVertexScore_CacheDecayPower );
}
}
return score;
}
float ComputeVertexValenceScore(size_t numActiveFaces)
{
const float FindVertexScore_ValenceBoostScale = 2.0f;
const float FindVertexScore_ValenceBoostPower = 0.5f;
float score = 0.0f;
// Bonus points for having a low number of tris still to
// use the vert, so we get rid of lone verts quickly.
float valenceBoost = powf ( static_cast<float>(numActiveFaces),
-FindVertexScore_ValenceBoostPower );
score += FindVertexScore_ValenceBoostScale * valenceBoost;
return score;
}
enum
{
kMaxVertexCacheSize = 64,
kMaxPrecomputedVertexValenceScores = 64
};
float s_vertexCacheScores[kMaxVertexCacheSize+1][kMaxVertexCacheSize];
float s_vertexValenceScores[kMaxPrecomputedVertexValenceScores];
bool ComputeVertexScores()
{
for (uint32_t cacheSize = 0; cacheSize <= kMaxVertexCacheSize; ++cacheSize)
{
for (uint32_t cachePos = 0; cachePos < cacheSize; ++cachePos)
{
s_vertexCacheScores[cacheSize][cachePos] = ComputeVertexCacheScore(cachePos, cacheSize);
}
}
for (uint32_t valence = 0; valence < kMaxPrecomputedVertexValenceScores; ++valence)
{
s_vertexValenceScores[valence] = ComputeVertexValenceScore(valence);
}
return true;
}
bool s_vertexScoresComputed = ComputeVertexScores();
inline float FindVertexCacheScore(size_t cachePosition, size_t maxSizeVertexCache)
{
return s_vertexCacheScores[maxSizeVertexCache][cachePosition];
}
inline float FindVertexValenceScore(size_t numActiveTris)
{
return s_vertexValenceScores[numActiveTris];
}
float FindVertexScore(size_t numActiveFaces, size_t cachePosition, size_t vertexCacheSize)
{
//ASSERT(s_vertexScoresComputed);
if (numActiveFaces == 0)
{
// No tri needs this vertex!
return -1.0f;
}
float score = 0.0f;
if (cachePosition < vertexCacheSize)
{
score += s_vertexCacheScores[vertexCacheSize][cachePosition];
}
if (numActiveFaces < kMaxPrecomputedVertexValenceScores)
{
score += s_vertexValenceScores[numActiveFaces];
}
else
{
score += ComputeVertexValenceScore(numActiveFaces);
}
return score;
}
struct OptimizeVertexData
{
float score;
size_t activeFaceListStart;
size_t activeFaceListSize;
size_t cachePos0;
size_t cachePos1;
OptimizeVertexData() : score(0.0f), activeFaceListStart(0), activeFaceListSize(0), cachePos0(0), cachePos1(0) { }
};
}
template <typename IndexType>
struct IndexSortCompareIndexed
{
const IndexType* _indexData;
IndexSortCompareIndexed(const IndexType* indexData)
: _indexData(indexData)
{
}
bool operator()(size_t a, size_t b) const
{
IndexType indexA = _indexData[a];
IndexType indexB = _indexData[b];
return indexA < indexB;
}
};
struct FaceValenceSort
{
const OptimizeVertexData* _vertexData;
FaceValenceSort(const OptimizeVertexData* vertexData)
: _vertexData(vertexData)
{
}
bool operator()(size_t a, size_t b) const
{
const OptimizeVertexData* vA0 = _vertexData + a * 3 + 0;
const OptimizeVertexData* vA1 = _vertexData + a * 3 + 1;
const OptimizeVertexData* vA2 = _vertexData + a * 3 + 2;
const OptimizeVertexData* vB0 = _vertexData + b * 3 + 0;
const OptimizeVertexData* vB1 = _vertexData + b * 3 + 1;
const OptimizeVertexData* vB2 = _vertexData + b * 3 + 2;
size_t aValence = vA0->activeFaceListSize + vA1->activeFaceListSize + vA2->activeFaceListSize;
size_t bValence = vB0->activeFaceListSize + vB1->activeFaceListSize + vB2->activeFaceListSize;
// higher scoring faces are those with lower valence totals
// reverse sort (reverse of reverse)
return aValence < bValence;
}
};
//-----------------------------------------------------------------------------
// OptimizeFaces
//-----------------------------------------------------------------------------
// Parameters:
// indexList
// input index list
// indexCount
// the number of indices in the list
// vertexCount
// the largest index value in indexList
// newIndexList
// a pointer to a preallocated buffer the same size as indexList to
// hold the optimized index list
// lruCacheSize
// the size of the simulated post-transform cache (max:64)
//-----------------------------------------------------------------------------
template <typename SrcIndexType, typename DstIndexType>
void OptimizeFaces(const SrcIndexType* indexList, size_t indexCount, DstIndexType* newIndexList, size_t lruCacheSize)
{
ASSERT(lruCacheSize <= kMaxVertexCacheSize);
std::unique_ptr<OptimizeVertexData[]> vertexDataList(new OptimizeVertexData[indexCount]); // upper bounds on size is indexCount
std::unique_ptr<uint32_t[]> vertexRemap(new uint32_t[indexCount]);
std::unique_ptr<uint32_t[]> activeFaceList(new uint32_t[indexCount]);
size_t faceCount = indexCount / 3;
std::unique_ptr<uint8_t[]> processedFaceList(new uint8_t[faceCount]);
memset(processedFaceList.get(), 0, sizeof(uint8_t) * faceCount);
std::unique_ptr<uint32_t[]> faceSorted(new uint32_t[faceCount]);
std::unique_ptr<uint32_t[]> faceReverseLookup(new uint32_t[faceCount]);
// build the vertex remap table
uint32_t uniqueVertexCount = 0;
{
typedef IndexSortCompareIndexed<SrcIndexType> indexSorter;
uint32_t* indexSorted = new uint32_t[indexCount];
for (uint32_t i = 0; i < indexCount; i++)
{
indexSorted[i] = i;
}
indexSorter sortFunc(indexList);
std::sort(indexSorted, indexSorted + indexCount, sortFunc);
for (uint32_t i = 0; i < indexCount; i++)
{
if (i == 0 || sortFunc(indexSorted[i - 1], indexSorted[i]))
{
// it's not a duplicate
vertexRemap[indexSorted[i]] = uniqueVertexCount;
uniqueVertexCount++;
}
else
{
vertexRemap[indexSorted[i]] = vertexRemap[indexSorted[i - 1]];
}
}
delete[] indexSorted;
}
// compute face count per vertex
for (size_t i = 0; i < indexCount; ++i)
{
vertexDataList[vertexRemap[i]].activeFaceListSize++;
}
const size_t kEvictedCacheIndex = std::numeric_limits<DstIndexType>::max();
{
// allocate face list per vertex
size_t curActiveFaceListPos = 0;
for (uint32_t i = 0; i < uniqueVertexCount; ++i)
{
OptimizeVertexData& vertexData = vertexDataList[i];
vertexData.cachePos0 = kEvictedCacheIndex;
vertexData.cachePos1 = kEvictedCacheIndex;
vertexData.activeFaceListStart = curActiveFaceListPos;
curActiveFaceListPos += vertexData.activeFaceListSize;
vertexData.score = FindVertexScore(vertexData.activeFaceListSize, vertexData.cachePos0, lruCacheSize);
vertexData.activeFaceListSize = 0;
}
ASSERT(curActiveFaceListPos == indexCount);
}
// sort unprocessed faces by highest score
for (uint32_t f = 0; f < faceCount; f++)
{
faceSorted[f] = f;
}
FaceValenceSort faceValenceSort(vertexDataList.get());
std::sort(faceSorted.get(), faceSorted.get() + faceCount, faceValenceSort);
for (uint32_t f = 0; f < faceCount; f++)
{
faceReverseLookup[faceSorted[f]] = f;
}
// fill out face list per vertex
for (uint32_t i=0; i<indexCount; i+=3)
{
for (size_t j=0; j<3; ++j)
{
OptimizeVertexData& vertexData = vertexDataList[vertexRemap[i + j]];
activeFaceList[vertexData.activeFaceListStart + vertexData.activeFaceListSize] = i;
vertexData.activeFaceListSize++;
}
}
uint32_t vertexCacheBuffer[(kMaxVertexCacheSize + 3) * 2];
uint32_t* cache0 = vertexCacheBuffer;
uint32_t* cache1 = vertexCacheBuffer + kMaxVertexCacheSize + 3;
size_t entriesInCache0 = 0;
uint32_t bestFace = 0;
float bestScore = -1.0f;
const float maxValenceScore = FindVertexScore(1, kEvictedCacheIndex, lruCacheSize) * 3.0f;
uint32_t nextBestFace = 0;
for (uint32_t i = 0; i < indexCount; i += 3)
{
if (bestScore < 0.0f)
{
// no verts in the cache are used by any unprocessed faces so
// search all unprocessed faces for a new starting point
for (; nextBestFace < faceCount; nextBestFace++)
{
uint32_t faceIndex = faceSorted[nextBestFace];
if (processedFaceList[faceIndex] == 0)
{
uint32_t face = faceIndex * 3;
float faceScore = 0.0f;
for (uint32_t k=0; k<3; ++k)
{
//ASSERT(vertexData.activeFaceListSize > 0);
//ASSERT(vertexData.cachePos0 >= lruCacheSize);
float vertexScore = vertexDataList[vertexRemap[face + k]].score;
faceScore += vertexScore;
}
bestScore = faceScore;
bestFace = face;
nextBestFace++;
break; // we're searching a pre-sorted list, first one we find will be the best
}
}
ASSERT(bestScore >= 0.0f);
}
processedFaceList[bestFace / 3] = 1;
size_t entriesInCache1 = 0;
// add bestFace to LRU cache and to newIndexList
for (uint32_t v = 0; v < 3; ++v)
{
uint32_t index = indexList[bestFace + v];
newIndexList[i+v] = (DstIndexType)index;
OptimizeVertexData& vertexData = vertexDataList[vertexRemap[bestFace + v]];
if (vertexData.cachePos1 >= entriesInCache1)
{
vertexData.cachePos1 = entriesInCache1;
cache1[entriesInCache1++] = vertexRemap[bestFace + v];
if (vertexData.activeFaceListSize == 1)
{
--vertexData.activeFaceListSize;
continue;
}
}
ASSERT(vertexData.activeFaceListSize > 0);
uint32_t* begin = activeFaceList.get() + vertexData.activeFaceListStart;
uint32_t* end = begin + vertexData.activeFaceListSize;
uint32_t* it = std::find(begin, end, bestFace);
ASSERT(it != end);
std::swap(*it, *(end-1));
--vertexData.activeFaceListSize;
vertexData.score = FindVertexScore(vertexData.activeFaceListSize, vertexData.cachePos1, lruCacheSize);
// need to re-sort the faces that use this vertex, as their score will change due to activeFaceListSize shrinking
for (uint32_t* fi = begin; fi != end - 1; ++fi)
{
uint32_t faceIndex = *fi / 3;
uint32_t n = faceReverseLookup[faceIndex];
ASSERT(faceSorted[n] == faceIndex);
// found it, now move it up
for (n; n > 0; --n)
{
if (!faceValenceSort(n, n - 1))
break;
faceReverseLookup[faceSorted[n]] = n - 1;
faceReverseLookup[faceSorted[n - 1]] = n;
std::swap(faceSorted[n], faceSorted[n - 1]);
}
}
}
// move the rest of the old verts in the cache down and compute their new scores
for (uint32_t c0 = 0; c0 < entriesInCache0; ++c0)
{
OptimizeVertexData& vertexData = vertexDataList[cache0[c0]];
if (vertexData.cachePos1 >= entriesInCache1)
{
vertexData.cachePos1 = entriesInCache1;
cache1[entriesInCache1++] = cache0[c0];
vertexData.score = FindVertexScore(vertexData.activeFaceListSize, vertexData.cachePos1, lruCacheSize);
// don't need to re-sort this vertex... once it gets out of the cache, it'll have its original score
}
}
// find the best scoring triangle in the current cache (including up to 3 that were just evicted)
bestScore = -1.0f;
for (uint32_t c1 = 0; c1 < entriesInCache1; ++c1)
{
OptimizeVertexData& vertexData = vertexDataList[cache1[c1]];
vertexData.cachePos0 = vertexData.cachePos1;
vertexData.cachePos1 = kEvictedCacheIndex;
for (uint32_t j = 0; j < vertexData.activeFaceListSize; ++j)
{
uint32_t face = activeFaceList[vertexData.activeFaceListStart+j];
float faceScore = 0.0f;
for (uint32_t v = 0; v < 3; ++v)
{
faceScore += vertexDataList[vertexRemap[face + v]].score;
}
if (faceScore > bestScore)
{
bestScore = faceScore;
bestFace = face;
}
}
}
std::swap(cache0, cache1);
entriesInCache0 = std::min(entriesInCache1, lruCacheSize);
}
}