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[Fix] (DirectVulkan): clamp fixed-point ReadPixels to [0,1]

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glReadPixels final conversion honors GL_CLAMP_READ_COLOR (default
GL_FIXED_ONLY): fixed-point normalized color buffers clamp to [0,1] on
read - visible for SNORM attachments, whose negative values previously
leaked through (texture_size_promotion SNORM cases). True float formats
stay unclamped unless the mode is GL_TRUE; GetTexImage is unaffected.
This commit is contained in:
BZLZHH
2026-08-01 01:15:57 -04:00
parent 95547ab9ce
commit 9ebbb76df1
1 changed files with 38 additions and 3 deletions
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MobileGL/MG_Backend/DirectVulkan/Renderer/VulkanRenderer.cpp
+38 -3
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@@ -2357,9 +2357,29 @@ void main() {
return true;
}
// True floating-point color formats are exempt from GL_FIXED_ONLY read clamping.
static Bool IsFloatingPointReadbackFormat(VkFormat format) {
switch (format) {
case VK_FORMAT_R16_SFLOAT:
case VK_FORMAT_R16G16_SFLOAT:
case VK_FORMAT_R16G16B16_SFLOAT:
case VK_FORMAT_R16G16B16A16_SFLOAT:
case VK_FORMAT_R32_SFLOAT:
case VK_FORMAT_R32G32_SFLOAT:
case VK_FORMAT_R32G32B32_SFLOAT:
case VK_FORMAT_R32G32B32A32_SFLOAT:
case VK_FORMAT_B10G11R11_UFLOAT_PACK32:
case VK_FORMAT_E5B9G9R9_UFLOAT_PACK32:
return true;
default:
return false;
}
}
static Bool PackReadbackToClientOrPbo(const Uint8* srcPixels, VkFormat srcFormat, GLsizei width,
GLsizei sliceHeight, GLsizei sliceCount, GLenum format, GLenum type,
void* pixels, Bool applyPackImageParams) {
void* pixels, Bool applyPackImageParams,
Bool applyReadColorClamp = false) {
if (width <= 0 || sliceHeight <= 0 || sliceCount <= 0) {
return true;
}
@@ -2380,6 +2400,21 @@ void main() {
return false;
}
// glReadPixels final conversion: GL_CLAMP_READ_COLOR defaults to GL_FIXED_ONLY,
// clamping fixed-point (normalized) buffers to [0,1] - visible for SNORM reads.
if (applyReadColorClamp && wideType == GL_FLOAT) {
const GLenum clampMode = MG_State::pGLContext->GetClampReadColor();
const Bool clamp = clampMode == GL_TRUE ||
(clampMode == GL_FIXED_ONLY && !IsFloatingPointReadbackFormat(srcFormat));
if (clamp) {
Float* values = reinterpret_cast<Float*>(wide.data());
const SizeT count = wide.size() / sizeof(Float);
for (SizeT i = 0; i < count; ++i) {
values[i] = std::min(std::max(values[i], 0.0f), 1.0f);
}
}
}
const Bool sourceIsInteger = wideType == GL_INT || wideType == GL_UNSIGNED_INT;
if (sourceIsInteger != mapping.isInteger) {
MGLOG_E("DirectVulkan readback skipped: integerness mismatch (format=0x%x source=%d)",
@@ -6937,7 +6972,7 @@ void main() {
sourceTexelSize,
remapped.data())) {
PackReadbackToClientOrPbo(remapped.data(), srcFormat, width, height, 1, format, type, pixels,
/*applyPackImageParams=*/false);
/*applyPackImageParams=*/false, /*applyReadColorClamp=*/true);
return;
}
}
@@ -6947,7 +6982,7 @@ void main() {
static_cast<Int>(preTransform));
}
PackReadbackToClientOrPbo(mapped, srcFormat, width, height, 1, format, type, pixels,
/*applyPackImageParams=*/false);
/*applyPackImageParams=*/false, /*applyReadColorClamp=*/true);
}
void VulkanRenderer::ReadDepthStencilPixels(MG_State::GLState::FramebufferObject& readFbo, GLint x, GLint y,