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Replace primitive restart index with degenerate triangles #456

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Merged
Gunoshozo merged 1 commit into from
Apr 27, 2026
Merged

Replace primitive restart index with degenerate triangles #456

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13 changes: 8 additions & 5 deletions src/effects/wave.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -18,11 +18,9 @@ void BGWave::Init() {
WaveData.resize(WaveMaxCount);
WavePos.resize((size_t)BGWaveGridSize.x * (size_t)BGWaveGridSize.y);
Vertices.resize((size_t)BGWaveGridSize.x * (size_t)BGWaveGridSize.y);
Indices.resize(
((size_t)BGWaveGridSize.x * 2 + 1) * ((size_t)BGWaveGridSize.y - 1) - 1);
Indices.resize((BGWaveGridSize.x * 2 + 2) * (BGWaveGridSize.y - 1) - 2);

// triangle strips with primitive restart index
constexpr uint16_t primitiveRestart = 0xFFFF;
// triangle strips with degenerate triangles for restarting a row
size_t i = 0;
for (uint16_t y = 0; y < BGWaveGridSize.y - 1; y++) {
for (uint16_t x = 0; x < BGWaveGridSize.x; x++) {
Expand All @@ -32,7 +30,12 @@ void BGWave::Init() {
}

if (y != BGWaveGridSize.y - 2) {
Indices[i++] = primitiveRestart;
const uint16_t lastIndex =
(y + 1) * BGWaveGridSize.x + (BGWaveGridSize.x - 1);
const uint16_t nextIndex = (y + 1) * BGWaveGridSize.x;

Indices[i++] = lastIndex;
Indices[i++] = nextIndex;
}
}
}
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12 changes: 2 additions & 10 deletions src/renderer/opengl/renderer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -284,15 +284,10 @@ void Renderer::InsertVertices(
const size_t indicesCount = indices.size();
IndexBuffer.resize(offset + indicesCount);

constexpr uint16_t restartIndex = 0xFFFF;
uint16_t maxIndex = 0;
for (size_t i = 0; i < indicesCount; ++i) {
if (indices[i] == restartIndex) {
IndexBuffer[i + offset] = restartIndex;
} else {
IndexBuffer[i + offset] = indices[i] + NextFreeIndex;
if (indices[i] > maxIndex) maxIndex = indices[i];
}
IndexBuffer[i + offset] = indices[i] + NextFreeIndex;
if (indices[i] > maxIndex) maxIndex = indices[i];
}

NextFreeIndex += maxIndex + 1;
Expand Down Expand Up @@ -972,13 +967,10 @@ void Renderer::Flush() {
default: // falls through
case TopologyMode::Triangles: {
mode = GL_TRIANGLES;
glDisable(GL_PRIMITIVE_RESTART);
break;
}
case TopologyMode::TriangleStrips: {
mode = GL_TRIANGLE_STRIP;
glPrimitiveRestartIndex(0xFFFF);
glEnable(GL_PRIMITIVE_RESTART);
break;
}
}
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