From 780240e6979b198e7bd10feaad5399b8b4b63762 Mon Sep 17 00:00:00 2001
From: Wollnashorn <Wollnashorn@users.noreply.github.com>
Date: Wed, 5 Apr 2023 01:29:46 +0200
Subject: shader_recompiler: Add subpixel offset for correct rounding at
`ImageGather` On AMD a subpixel offset of 1/512 of the texel size is applied
to the texture coordinates at a ImageGather call to ensure the rounding at
the texel centers is done the same way as in Maxwell or other Nvidia
architectures. See
https://www.reedbeta.com/blog/texture-gathers-and-coordinate-precision/ for
more details why this might be necessary.
This should fix shadow artifacts at object edges in Zelda: Breath of the Wild (#9957, #6956).
---
.../backend/glsl/emit_glsl_image.cpp | 29 ++++++++++++++++++++++
1 file changed, 29 insertions(+)
(limited to 'src/shader_recompiler/backend/glsl/emit_glsl_image.cpp')
diff --git a/src/shader_recompiler/backend/glsl/emit_glsl_image.cpp b/src/shader_recompiler/backend/glsl/emit_glsl_image.cpp
index f335c8af04..418505475e 100644
--- a/src/shader_recompiler/backend/glsl/emit_glsl_image.cpp
+++ b/src/shader_recompiler/backend/glsl/emit_glsl_image.cpp
@@ -143,6 +143,21 @@ IR::Inst* PrepareSparse(IR::Inst& inst) {
}
return sparse_inst;
}
+
+std::string ImageGatherSubpixelOffset(const IR::TextureInstInfo& info, std::string_view texture,
+ std::string_view coords) {
+ switch (info.type) {
+ case TextureType::Color2D:
+ case TextureType::Color2DRect:
+ return fmt::format("{}+vec2(0.001953125)/vec2(textureSize({}, 0))", coords, texture);
+ case TextureType::ColorArray2D:
+ case TextureType::ColorCube:
+ return fmt::format("vec3({0}.xy+vec2(0.001953125)/vec2(textureSize({1}, 0)),{0}.z)", coords,
+ texture);
+ default:
+ return std::string{coords};
+ }
+}
} // Anonymous namespace
void EmitImageSampleImplicitLod(EmitContext& ctx, IR::Inst& inst, const IR::Value& index,
@@ -340,6 +355,13 @@ void EmitImageGather(EmitContext& ctx, IR::Inst& inst, const IR::Value& index,
LOG_WARNING(Shader_GLSL, "Device does not support sparse texture queries. STUBBING");
ctx.AddU1("{}=true;", *sparse_inst);
}
+ std::string coords_with_subpixel_offset;
+ if (ctx.profile.need_gather_subpixel_offset) {
+ // Apply a subpixel offset of 1/512 the texel size of the texture to ensure same rounding on
+ // AMD hardware as on Maxwell or other Nvidia architectures.
+ coords_with_subpixel_offset = ImageGatherSubpixelOffset(info, texture, coords);
+ coords = coords_with_subpixel_offset;
+ }
if (!sparse_inst || !supports_sparse) {
if (offset.IsEmpty()) {
ctx.Add("{}=textureGather({},{},int({}));", texel, texture, coords,
@@ -387,6 +409,13 @@ void EmitImageGatherDref(EmitContext& ctx, IR::Inst& inst, const IR::Value& inde
LOG_WARNING(Shader_GLSL, "Device does not support sparse texture queries. STUBBING");
ctx.AddU1("{}=true;", *sparse_inst);
}
+ std::string coords_with_subpixel_offset;
+ if (ctx.profile.need_gather_subpixel_offset) {
+ // Apply a subpixel offset of 1/512 the texel size of the texture to ensure same rounding on
+ // AMD hardware as on Maxwell or other Nvidia architectures.
+ coords_with_subpixel_offset = ImageGatherSubpixelOffset(info, texture, coords);
+ coords = coords_with_subpixel_offset;
+ }
if (!sparse_inst || !supports_sparse) {
if (offset.IsEmpty()) {
ctx.Add("{}=textureGather({},{},{});", texel, texture, coords, dref);
--
cgit v1.2.3-70-g09d2