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[Fix, Test] (DirectGLES, DirectVulkan): narrow GL_DOUBLE vertex arrays to float32 instead of dropping them

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swung0x48
2026-08-20 23:54:49 -04:00
parent 1b5a39473e
commit 7aa91e8024
8 changed files with 436 additions and 62 deletions
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MobileGL/MG_Impl/GLImpl/VertexArray/GL_VertexArray.cpp
+14 -12
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@@ -514,15 +514,17 @@ namespace MobileGL::MG_Impl::GLImpl {
// recorded DataType is always Float64 - what IsLong adds is that this is the *unconverted* form,
// as opposed to VertexAttribFormat(GL_DOUBLE), which asks for a float conversion.
//
// Whether the backend can FEED it is detected, not assumed: DirectVulkan needs shaderFloat64,
// and DirectGLES can never have it at all. What that costs is the ARRAY, not the call: GL 4.6
// core 10.3.2 defines no error for a well-formed glVertexAttribLFormat, and a GL 4.3 context
// has 64-bit attributes in core, so declining the call would be non-conformant and would make
// the four pure state queries (VERTEX_ATTRIB_ARRAY_SIZE / _TYPE / _LONG / _RELATIVE_OFFSET)
// unanswerable (KHR-GL43.vertex_attrib_binding.basic-state1/3). The format is therefore
// RECORDED here and the enabled array is dropped at draw instead - loudly, once, naming the
// reason. The matching startup POST row is in MG_Util/SelfTest/DriverPost.cpp; the draw-side
// drop is DirectGLES/Managers.cpp and, on DirectVulkan, VertexInputStateFactory's Float64 case.
// Whether the backend can FEED it at full precision is detected, not assumed: DirectVulkan
// needs shaderFloat64, and DirectGLES can never have it at all. What that costs is PRECISION,
// not the call and no longer the array: GL 4.6 core 10.3.2 defines no error for a well-formed
// glVertexAttribLFormat, and a GL 4.3 context has 64-bit attributes in core, so declining the
// call would be non-conformant and would make the four pure state queries
// (VERTEX_ATTRIB_ARRAY_SIZE / _TYPE / _LONG / _RELATIVE_OFFSET) unanswerable
// (KHR-GL43.vertex_attrib_binding.basic-state1/3). The format is therefore RECORDED here and
// the array is NARROWED to float32 at draw, matching the fp64 demotion every shader already
// gets (DemoteFloat64Pass) - loudly, once, naming the cost. The matching startup POST row is in
// MG_Util/SelfTest/DriverPost.cpp; the draw-side narrowing is DirectGLES/Managers.cpp and, on
// DirectVulkan, VertexInputStateFactory's Float64 case.
static void VertexAttribLFormatSeparate_State(const SharedPtr<MG_State::GLState::VertexArrayObject>& vao,
GLuint attribindex, GLint size, GLenum type,
GLuint relativeoffset) {
@@ -534,9 +536,9 @@ namespace MobileGL::MG_Impl::GLImpl {
!MG_Backend::pActiveBackendObject->GetDynamicParameters().SupportsFloat64VertexAttributes) {
MGLOG_W_ONCE("VertexAttribLFormat: attribute %u asked for a 64-bit (GL_DOUBLE) format, but this "
"backend has no double-precision vertex attribute support - the format is recorded "
"and queryable, but the array will be DROPPED at draw and the attribute will read "
"its generic current value; see the \"64-bit vertex attributes\" / \"shaderFloat64\" "
"POST row for what that costs",
"and queryable, and the array is FETCHED AT FLOAT32 PRECISION at draw (the same "
"narrowing the shader's dvec inputs already get); see the \"64-bit vertex "
"attributes\" / \"shaderFloat64\" POST row for what that costs",
attribindex);
}