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[Fix] (Tessellation): bound the pass-through control-stage cache and stop baking "draw nothing" for levels GL clamps

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This commit is contained in:
Swung0x48
2026-08-27 03:18:14 -04:00
parent 2635fe84b6
commit 31252cf0da
7 changed files with 104 additions and 52 deletions
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MobileGL/MG_Backend/DirectVulkan/Renderer/ProgramFactory.cpp
+22 -15
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@@ -3597,19 +3597,6 @@ namespace MobileGL::MG_Backend::DirectVulkan {
}
}
namespace {
// A GLSL float literal for a tessellation level. Always spelled with a decimal point,
// because an integral value written without one is an INT literal and
// `gl_TessLevelOuter[0] = 1;` does not compile. A non-finite value is baked as 0.0:
// glPatchParameterfv accepts any float, and a level that is not a positive number
// discards the patch - which is what a NaN level does in GL too - whereas emitting "nan"
// would make the synthesized stage fail to compile and take the whole program down.
String TessLevelLiteral(Float value) {
if (!std::isfinite(value)) return "0.0";
return std::format("{:.6f}", value);
}
} // namespace
Uint64 ProgramFactory::ComputePassthroughTessControlKey(Uint32 patchVertices,
const FloatVec4& defaultOuterLevel,
const FloatVec2& defaultInnerLevel) {
@@ -3683,11 +3670,11 @@ namespace MobileGL::MG_Backend::DirectVulkan {
source += " gl_out[gl_InvocationID].gl_Position = gl_in[gl_InvocationID].gl_Position;\n";
for (Uint32 i = 0; i < 4; ++i) {
source += " gl_TessLevelOuter[" + std::to_string(i) +
"] = " + TessLevelLiteral(defaultOuterLevel[i]) + ";\n";
"] = " + MG_Util::ShaderTranspiler::TessellationLevelLiteral(defaultOuterLevel[i]) + ";\n";
}
for (Uint32 i = 0; i < 2; ++i) {
source += " gl_TessLevelInner[" + std::to_string(i) +
"] = " + TessLevelLiteral(defaultInnerLevel[i]) + ";\n";
"] = " + MG_Util::ShaderTranspiler::TessellationLevelLiteral(defaultInnerLevel[i]) + ";\n";
}
source += "}\n";
return source;
@@ -3707,6 +3694,26 @@ namespace MobileGL::MG_Backend::DirectVulkan {
return cached->second;
}
// The key stopped being bounded when the levels joined it: patchVertices alone could only
// take 32 values, but six unclamped application floats can take any number, and an
// application that ramps a level per frame would retain one VkShaderModule per frame for
// the lifetime of the device. Flushed wholesale rather than aged: a module is not
// referenced by the pipelines built from it (Vulkan copies what it needs at
// vkCreateGraphicsPipelines), everything here runs on the GL thread, and an application
// that can overflow this cap is already recompiling every frame - so the flush costs it
// nothing it was not paying anyway.
if (m_passthroughTessControlStages.size() >= kMaxPassthroughTessControlStages) {
MGLOG_D("ProgramFactory: flushing %zu pass-through tessellation control stages; the application has "
"used more than %zu distinct (patch size, default level) combinations",
m_passthroughTessControlStages.size(), kMaxPassthroughTessControlStages);
for (auto& entry : m_passthroughTessControlStages) {
if (entry.second.module != VK_NULL_HANDLE) {
vkDestroyShaderModule(m_device, entry.second.module, nullptr);
}
}
m_passthroughTessControlStages.clear();
}
VkPipelineShaderStageCreateInfo stage{VK_STRUCTURE_TYPE_PIPELINE_SHADER_STAGE_CREATE_INFO};
stage.stage = VK_SHADER_STAGE_TESSELLATION_CONTROL_BIT;
stage.module = VK_NULL_HANDLE;