Add WorldPosition to postfx material scene textures for world-space position sampling at uv

Content/Editor/MaterialTemplates/PostProcess.shader

@@ -18,6 +18,7 @@ float TimeParam;
 float4 ViewInfo;
 float4 ScreenSize;
 float4 TemporalAAJitter;
+float4x4 InverseViewProjectionMatrix;
 @1META_CB_END
 
 // Shader resources
@@ -62,6 +63,14 @@ MaterialInput GetMaterialInput(PixelInput input)
 	return result;
 }
 
+// Gets world space position at given pixel coordinate with given device depth
+float3 GetWorldPos(float2 uv, float deviceDepth)
+{
+	float4 clipPos = float4(uv * float2(2.0, -2.0) + float2(-1.0, 1.0), deviceDepth, 1.0);
+	float4 wsPos = mul(clipPos, InverseViewProjectionMatrix);
+	return wsPos.xyz / wsPos.w;
+}
+
 // Transforms a vector from tangent space to world space
 float3 TransformTangentVectorToWorld(MaterialInput input, float3 tangentVector)
 {