From 721731a24f808e9405abc89281ed77e5dc1f3152 Mon Sep 17 00:00:00 2001
From: doodlum <15017472+doodlum@users.noreply.github.com>
Date: Sun, 13 Oct 2024 15:39:59 +0100
Subject: [PATCH] fix: sky motion vectors (#638)
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* fix: sky motion vectors

* style: 🎨 apply clang-format changes

---------

Co-authored-by: doodlum <doodlum@users.noreply.github.com>
---
 package/Shaders/Sky.hlsl | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/package/Shaders/Sky.hlsl b/package/Shaders/Sky.hlsl
index 7805c84a2..a0be92e28 100644
--- a/package/Shaders/Sky.hlsl
+++ b/package/Shaders/Sky.hlsl
@@ -241,7 +241,15 @@ PS_OUTPUT main(PS_INPUT input)
 	psout.Color = float4(0, 0, 0, 1.0);
 #	endif  // OCCLUSION
 
-	float2 screenMotionVector = GetSSMotionVector(input.WorldPosition, input.PreviousWorldPosition, eyeIndex);
+	float3 viewPosition = mul(CameraView[eyeIndex], float4(input.WorldPosition.xyz, 1)).xyz;
+	float2 screenUV = FrameBuffer::ViewToUV(viewPosition, true, eyeIndex);
+
+	float4 positionWS = half4(2 * half2(screenUV.x, -screenUV.y + 1) - 1, 1.0, 1);
+	positionWS = mul(CameraViewProjInverse[eyeIndex], positionWS);
+	positionWS.xyz = positionWS.xyz / positionWS.w;
+	positionWS.w = 1;
+
+	float2 screenMotionVector = GetSSMotionVector(positionWS, positionWS, eyeIndex);
 
 	psout.MotionVectors = float4(screenMotionVector, 0, psout.Color.w);
 	psout.Normal = float4(0.5, 0.5, 0, psout.Color.w);