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Fix half pixel screwing up SSAA samples #361

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Merged
IsaacMarovitz merged 1 commit into from
Nov 8, 2026
+16 −20
Merged

Fix half pixel screwing up SSAA samples #361

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18 changes: 8 additions & 10 deletions MarathonRecomp/gpu/shader/hlsl/downsample_ps.hlsl
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Original file line number Diff line number Diff line change
Expand Up @@ -3,12 +3,14 @@
#ifdef __spirv__

#define s0_Texture2DDescriptorIndex vk::RawBufferLoad<uint>(g_PushConstants.SharedConstants + 0)
#define s0_SamplerDescriptorIndex vk::RawBufferLoad<uint>(g_PushConstants.SharedConstants + 192)

#else

cbuffer SharedConstants : register(b2, space4)
{
uint s0_Texture2DDescriptorIndex : packoffset(c0.x);
uint s0_SamplerDescriptorIndex : packoffset(c12.x);
DEFINE_SHARED_CONSTANTS();
};

Expand All @@ -19,17 +21,13 @@ float4 shaderMain(
in float4 oTexCoord0 : TEXCOORD0) : SV_Target
{
Texture2D<float4> texture = g_Texture2DDescriptorHeap[s0_Texture2DDescriptorIndex];
SamplerState samplerState = g_SamplerDescriptorHeap[s0_SamplerDescriptorIndex];

float2 pixelCoord = oTexCoord0.xy * float2(getTexture2DDimensions(texture));
float2 step = float2(ddx(pixelCoord.x), ddy(pixelCoord.y)) / 2.0;
float2 dimensions = float2(getTexture2DDimensions(texture));
float2 pixelCoord = oTexCoord0.xy * dimensions;
float2 texelsPerPixel = float2(ddx(pixelCoord.x), ddy(pixelCoord.y));

float4 color = 0.0;
pixelCoord += (texelsPerPixel - 1.0) * 0.5;

for (int y = 0; y < 2; y++)
{
for (int x = 0; x < 2; x++)
color += texture.Load(int3(int2(pixelCoord + (float2(x, y) - 0.5) * step), 0));
}

return color / 4.0;
return texture.Sample(samplerState, pixelCoord / dimensions);
}
18 changes: 8 additions & 10 deletions MarathonRecomp/gpu/shader/msl/downsample_ps.metal
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
#include "../../../../tools/XenosRecomp/XenosRecomp/shader_common.h"

#define s0_TextureDescriptorIndex (*(reinterpret_cast<device int*>(g_PushConstants.SharedConstants + 0)))
#define s0_SamplerDescriptorIndex (*(reinterpret_cast<device uint*>(g_PushConstants.SharedConstants + 192)))

struct Interpolators
{
Expand All @@ -11,20 +12,17 @@ struct Interpolators
[[fragment]]
float4 shaderMain(Interpolators input [[stage_in]],
constant Texture2DDescriptorHeap* g_Texture2DDescriptorHeap [[buffer(0)]],
constant SamplerDescriptorHeap* g_SamplerDescriptorHeap [[buffer(3)]],
constant PushConstants& g_PushConstants [[buffer(8)]])
{
texture2d<float> texture = g_Texture2DDescriptorHeap[s0_TextureDescriptorIndex].tex;
sampler samp = g_SamplerDescriptorHeap[s0_SamplerDescriptorIndex].samp;

float2 pixelCoord = input.oTexCoord0.xy * float2(getTexture2DDimensions(texture));
float2 step = float2(dfdx(pixelCoord.x), dfdy(pixelCoord.y)) / 2.0;
float2 dimensions = float2(getTexture2DDimensions(texture));
float2 pixelCoord = input.oTexCoord0.xy * dimensions;
float2 texelsPerPixel = float2(dfdx(pixelCoord.x), dfdy(pixelCoord.y));

float4 color = 0.0;
pixelCoord += (texelsPerPixel - 1.0) * 0.5;

for (int y = 0; y < 2; y++)
{
for (int x = 0; x < 2; x++)
color += texture.read(uint2(pixelCoord + (float2(x, y) - 0.5) * step));
}

return color / 4.0;
return texture.sample(samp, pixelCoord / dimensions);
}
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