void OptimizeIndices(ModelSubGeometryLodLevel* subGeom, ModelVertexBuffer* vb, ModelIndexBuffer* ib)
{
PODVector<Triangle> oldTriangles;
PODVector<Triangle> newTriangles;
if (subGeom->indexCount_ % 3)
{
PrintLine("Index count is not divisible by 3, skipping index optimization");
return;
}
for (unsigned i = 0; i < vb->vertices_.Size(); ++i)
{
vb->vertices_[i].useCount_ = 0;
vb->vertices_[i].cachePosition_ = -1;
}
for (unsigned i = subGeom->indexStart_; i < subGeom->indexStart_ + subGeom->indexCount_; i += 3)
{
Triangle triangle;
triangle.v0_ = ib->indices_[i];
triangle.v1_ = ib->indices_[i + 1];
triangle.v2_ = ib->indices_[i + 2];
vb->vertices_[triangle.v0_].useCount_++;
vb->vertices_[triangle.v1_].useCount_++;
vb->vertices_[triangle.v2_].useCount_++;
oldTriangles.Push(triangle);
}
for (unsigned i = 0; i < vb->vertices_.Size(); ++i)
CalculateScore(vb->vertices_[i]);
PODVector<unsigned> vertexCache;
while (oldTriangles.Size())
{
unsigned bestTriangle = M_MAX_UNSIGNED;
float bestTriangleScore = -1.0f;
// Find the best triangle at this point
for (unsigned i = 0; i < oldTriangles.Size(); ++i)
{
Triangle& triangle = oldTriangles[i];
float triangleScore =
vb->vertices_[triangle.v0_].score_ +
vb->vertices_[triangle.v1_].score_ +
vb->vertices_[triangle.v2_].score_;
if (triangleScore > bestTriangleScore)
{
bestTriangle = i;
bestTriangleScore = triangleScore;
}
}
if (bestTriangle == M_MAX_UNSIGNED)
{
PrintLine("Could not find next triangle, aborting index optimization");
return;
}
// Add the best triangle
Triangle triangleCopy = oldTriangles[bestTriangle];
newTriangles.Push(triangleCopy);
oldTriangles.Erase(oldTriangles.Begin() + bestTriangle);
// Reduce the use count
vb->vertices_[triangleCopy.v0_].useCount_--;
vb->vertices_[triangleCopy.v1_].useCount_--;
vb->vertices_[triangleCopy.v2_].useCount_--;
// Model the LRU cache behaviour
// Erase the triangle vertices from the middle of the cache, if they were there
for (unsigned i = 0; i < vertexCache.Size(); ++i)
{
if ((vertexCache[i] == triangleCopy.v0_) ||
(vertexCache[i] == triangleCopy.v1_) ||
(vertexCache[i] == triangleCopy.v2_))
{
vertexCache.Erase(vertexCache.Begin() + i);
--i;
}
}
// Then push them to the front
vertexCache.Insert(vertexCache.Begin(), triangleCopy.v0_);
vertexCache.Insert(vertexCache.Begin(), triangleCopy.v1_);
vertexCache.Insert(vertexCache.Begin(), triangleCopy.v2_);
// Update positions & scores of all vertices in the cache
// Give position -1 if vertex is going to be erased
for (unsigned i = 0; i < vertexCache.Size(); ++i)
{
ModelVertex& vertex = vb->vertices_[vertexCache[i]];
if (i >= VERTEX_CACHE_SIZE)
vertex.cachePosition_ = -1;
else
vertex.cachePosition_ = i;
CalculateScore(vertex);
}
// Finally erase the extra vertices
if (vertexCache.Size() > VERTEX_CACHE_SIZE)
vertexCache.Resize(VERTEX_CACHE_SIZE);
}
// Rewrite the index data now
unsigned i = subGeom->indexStart_;
for (unsigned j = 0; j < newTriangles.Size(); ++j)
{
ib->indices_[i++] = newTriangles[j].v0_;
ib->indices_[i++] = newTriangles[j].v1_;
ib->indices_[i++] = newTriangles[j].v2_;
}
}
