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[Fix] (DirectGLES, MG_Util): keep 16-bit SNORM precision through the widening

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GL_RGB16_SNORM widened to GL_RGBA16F to stay renderable as multisample storage, and
a half float's 11-bit mantissa cannot hold a 16-bit signed-normalized channel:
KHR-GL33.texture_swizzle's blue channel came back several units of 32767 away from
the value the reference computes, well outside its one-unit tolerance.

GL_EXT_render_snorm makes the signed-normalized formats colour-renderable on ES, so
widen to GL_RGBA16_SNORM instead wherever it and EXT_texture_norm16 are both
present, and only fall back to the half float otherwise. Threaded through as its own
normalize option so the capability probe and the runtime pick the same format, the
way every other driver-dependent substitution here is decided.
This commit is contained in:
BZLZHH
2026-08-02 04:24:23 -04:00
parent a687873d32
commit e45f7ae5d4
6 changed files with 40 additions and 7 deletions
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MobileGL/MG_Util/Texture/TextureFormatProcessor.cpp
+8 -1
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@@ -36,6 +36,9 @@ namespace MobileGL::MG_Util::TextureFormatProcessor {
applicableOptions |= options & PixelFormatNormalizeOptionBit::NoNorm16;
applicableOptions |= options & PixelFormatNormalizeOptionBit::NoSnorm16;
applicableOptions |= options & PixelFormatNormalizeOptionBit::NoThreeChannelRenderTarget;
if (options & PixelFormatNormalizeOptionBit::NoThreeChannelRenderTarget) {
applicableOptions |= options & PixelFormatNormalizeOptionBit::NoSnorm16RenderTarget;
}
break;
case GL_RGBA16_SNORM:
case GL_RG16_SNORM:
@@ -130,7 +133,11 @@ namespace MobileGL::MG_Util::TextureFormatProcessor {
break;
case GL_RGB16_SNORM:
if (options & PixelFormatNormalizeOptionBit::NoThreeChannelRenderTarget) {
*outInternalFormat = GL_RGBA16F;
// A half float loses the low bits of a 16-bit SNORM channel, so keep the
// signed-normalized encoding whenever the driver can render to it.
*outInternalFormat = (options & PixelFormatNormalizeOptionBit::NoSnorm16RenderTarget)
? GL_RGBA16F
: GL_RGBA16_SNORM;
break;
}
if ((options & PixelFormatNormalizeOptionBit::NoNorm16) ||