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fix(TAA): restore VR per-eye reprojection and opaque alpha #84

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Merged
alandtse merged 2 commits into from
Jun 3, 2026
Merged

fix(TAA): restore VR per-eye reprojection and opaque alpha #84

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2e32ec2
fix(TAA): restore VR per-eye reprojection and opaque alpha
alandtse Jun 3, 2026
882b9d8
docs(TAA): tighten VR fix comments to repo standard
alandtse Jun 3, 2026
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27 changes: 21 additions & 6 deletions package/Shaders/ISTemporalAA.hlsl
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@
#include "Common/DisplayMapping.hlsli"
#include "Common/DummyVSTexCoord.hlsl"
#include "Common/FrameBuffer.hlsli"
#include "Common/VR.hlsli"

typedef VS_OUTPUT PS_INPUT;

Expand Down Expand Up @@ -264,9 +265,20 @@ PS_OUTPUT main(PS_INPUT input)
// --- motion vector and history sample ---
history.xy = drMax;
motionReject.xy = velocityTex.Sample(velocitySampler, ClampScreenUV(motionReject.xy, history.xy)).xy;
# ifdef VR
// Both eyes share one render target in VR, so reprojection must stay within the current
// eye: Stereo::ApplyVelocityToUV converts to mono, applies velocity, clamps per-eye, and
// maps back. Plain texCoord+velocity (the SE path) lets a pixel near the x=0.5 seam sample
// the other eye's history (cross-eye ghosting). GetPreviousDynamicResolutionAdjustedScreen-
// Position keeps the DR history clamp per-eye too; prevUVOutOfBounds drives rejection below.
bool prevUVOutOfBounds;
float2 prevUV = Stereo::ApplyVelocityToUV(texCoord.xy, motionReject.xy, prevUVOutOfBounds);
tapMin.xy = FrameBuffer::GetPreviousDynamicResolutionAdjustedScreenPosition(prevUV);
# else
motionReject.zw = texCoord.xy + motionReject.xy;
motionReject.x = sqrt(dot(motionReject.xy, motionReject.xy));
tapMin.xy = ClampHistoryUV(motionReject.zw);
# endif
motionReject.x = sqrt(dot(motionReject.xy, motionReject.xy));
history.xyw = historyTex.Sample(historySampler, tapMin.xy).xyz;
# ifdef HDR_OUTPUT
// history.x is stored as game-gamma luma (see EncodeFeedbackLuma on write).
Expand Down Expand Up @@ -418,12 +430,18 @@ PS_OUTPUT main(PS_INPUT input)
corner.xyz = history.yyy * corner.xyz + tapMin.xyz;

// --- disocclusion / mask rejection ---
// motionReject.zw still holds reprojected UV from motion pass; motionReject.x = motion length
// motionReject.x = motion length (motionReject.zw held the reprojected UV on the SE path).
# ifdef VR
// Out-of-bounds was already resolved per-eye in mono space (Stereo::ApplyVelocityToUV); the
// stereo-space [0,1] test used on the SE path would miss the x=0.5 eye seam.
motionReject.z = prevUVOutOfBounds ? 1 : 0;
# else
sampleUV.w = min(motionReject.z, motionReject.w);
motionReject.zw = cmp(motionReject.zw >= float2(1, 1));
sampleUV.w = cmp(0 >= sampleUV.w);
motionReject.z = (int)motionReject.z | (int)sampleUV.w;
motionReject.z = (int)motionReject.w | (int)motionReject.z;
# endif
history.yz = maskTex.Sample(maskSampler, sampleUV.xy).xy;
motionReject.w = AlphaCoverageMask(sampleUV.xy);
sampleUV.x = cmp(ThresholdParams.w < history.z);
Expand Down Expand Up @@ -513,11 +531,8 @@ PS_OUTPUT main(PS_INPUT input)
# else
feedbackOut.x = saturate(sampleUV.x * motionReject.z);
# endif
# if defined(VR)
colorOut.w = motionReject.x ? 1 : 0;
# else
// Vanilla writes opaque alpha unconditionally on both SE and VR (decompile o0.w = 1).
colorOut.w = 1;
# endif
feedbackOut.w = 1;

# ifdef HDR_OUTPUT
Expand Down
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