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Optimize sphere rendering using degenerate triangles 

Total time to render a 640x480 frame drops from 6.8 ms (6.2 the best case)
to 2.7 ms (2.8 the worst case) (tested on Intel UHD Graphics 620)
pull/753/head
Hleb Valoshka 2020-05-22 19:09:36 +03:00
parent cdb7529563
commit 7a062af1ec
1 changed files with 16 additions and 9 deletions
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25
src/celengine/lodspheremesh.cpp
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@ -111,7 +111,8 @@ LODSphereMesh::LODSphereMesh()
maxVertices = (maxPhiSteps + 1) * (maxThetaSteps + 1);
vertices = new float[MaxVertexSize * maxVertices];
nIndices = maxPhiSteps * 2 * (maxThetaSteps + 1);
nIndices = maxPhiSteps * 2 * (maxThetaSteps + 2) - 2;
assert(nIndices < numeric_limits<unsigned short>::max());
indices = new unsigned short[nIndices];
}
@ -267,12 +268,22 @@ void LODSphereMesh::render(unsigned int attributes,
int n2 = 0;
for (i = 0; i < nRings; i++)
{
if (i > 0)
{
indices[n2 + 0] = i * (nSlices + 1) + 0;
n2++;
}
for (int j = 0; j <= nSlices; j++)
{
indices[n2 + 0] = i * (nSlices + 1) + j;
indices[n2 + 1] = (i + 1) * (nSlices + 1) + j;
n2 += 2;
}
if (i < nRings - 1)
{
indices[n2] = (i + 1) * (nSlices + 1) + nSlices;
n2++;
}
}
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexBuffer);
@ -605,14 +616,10 @@ void LODSphereMesh::renderSection(int phi0, int theta0, int extent,
int nRings = phiExtent / ri.step;
int nSlices = thetaExtent / ri.step;
unsigned short* indexBase = nullptr;
for (int i = 0; i < nRings; i++)
{
glDrawElements(GL_TRIANGLE_STRIP,
(nSlices + 1) * 2,
GL_UNSIGNED_SHORT,
indexBase + (nSlices + 1) * 2 * i);
}
glDrawElements(GL_TRIANGLE_STRIP,
nRings * (nSlices + 2) * 2 - 2,
GL_UNSIGNED_SHORT,
nullptr);
// Cycle through the vertex buffers
currentVB++;