Fix T97086: corrupted UVs with GPU subdivision
When multiple objects are in edit mode, UVs for the objects, except for the first one (in rendering order) appear corrupted. The corruption is because the UVs are not evaluated as the compute shader is not bound, thus we read unitialized memory. We keep track of the currently bound shader in the GPU context in order to avoid unnecessary shader switches in case the same shader is used in consecutive calls. However, the shader used by the OpenSubdiv evaluator is not part of Blender and therefore not tracked via the GPU context. When extracting UVs for multiple objects, we only ever run a single shader (FVar evaluation). However, between the compute calls, we also call the OpenSubdiv stencil evaluation shader, which uses `glUseProgram` modifying the current program, outside of our control, which then also unbinds the Blender compute shader making the compute dispatch fail ("No active compute shader"). The fact that extracting the UVs for the first rendered object works is because another (Blender) shader was bound in the GPU context prior to our binding of our evaluation shader. To fix this, we remember, in the OpenSubdiv evaluator, the current program so that it can be reset after the stencil program is done. Differential Revision: https://developer.blender.org/D15064
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Notes:
blender-bot
2023-02-14 08:06:33 +01:00
Referenced by issue #97086, GPU subdivision: UVs display wrong with multiple objects in edit mode
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@ -396,6 +396,8 @@ bool GLComputeEvaluator::EvalStencils(GLuint srcBuffer,
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if (dvvWeightsBuffer)
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glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 15, dvvWeightsBuffer);
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GLint activeProgram;
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glGetIntegerv(GL_CURRENT_PROGRAM, &activeProgram);
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glUseProgram(_stencilKernel.program);
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glUniform1i(_stencilKernel.uniformStart, start);
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@ -420,7 +422,7 @@ bool GLComputeEvaluator::EvalStencils(GLuint srcBuffer,
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DispatchCompute(count);
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glUseProgram(0);
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glUseProgram(activeProgram);
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glMemoryBarrier(GL_TEXTURE_FETCH_BARRIER_BIT);
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for (int i = 0; i < 16; ++i) {
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@ -501,6 +503,8 @@ bool GLComputeEvaluator::EvalPatches(GLuint srcBuffer,
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glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 6, patchIndexBuffer);
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glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 7, patchParamsBuffer);
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GLint activeProgram;
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glGetIntegerv(GL_CURRENT_PROGRAM, &activeProgram);
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glUseProgram(_patchKernel.program);
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glUniform1i(_patchKernel.uniformSrcOffset, srcDesc.offset);
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@ -534,7 +538,7 @@ bool GLComputeEvaluator::EvalPatches(GLuint srcBuffer,
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DispatchCompute(numPatchCoords);
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glUseProgram(0);
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glUseProgram(activeProgram);
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glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 0, 0);
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glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 1, 0);
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