feat(VR): enable SSR (#502)

package/Shaders/Common/FrameBuffer.hlsli

@@ -1,3 +1,6 @@
+#ifndef __FRAMEBUFFER_DEPENDENCY_HLSL__
+#define __FRAMEBUFFER_DEPENDENCY_HLSL__
+
 cbuffer PerFrame : register(b12)
 {
 #if !defined(VR)
@@ -47,26 +50,39 @@ cbuffer PerFrame : register(b12)
 #endif  // !VR
 }
 
-float2 GetDynamicResolutionAdjustedScreenPosition(float2 screenPosition)
+float2 GetDynamicResolutionAdjustedScreenPosition(float2 screenPosition, uint stereo = 1)
 {
 	float2 screenPositionDR = DynamicResolutionParams1.xy * screenPosition;
 	float2 minValue = 0;
 	float2 maxValue = float2(DynamicResolutionParams2.z, DynamicResolutionParams1.y);
 #if defined(VR)
-	bool isRight = screenPosition.x >= 0.5;
-	float minFactor = isRight ? 1 : 0;
-	minValue.x = 0.5 * (DynamicResolutionParams2.z * minFactor);
-	float maxFactor = isRight ? 2 : 1;
-	maxValue.x = 0.5 * (DynamicResolutionParams2.z * maxFactor);
+	// VR sometimes will clamp to stereouv
+	if (stereo) {
+		bool isRight = screenPosition.x >= 0.5;
+		float minFactor = isRight ? 1 : 0;
+		minValue.x = 0.5 * (DynamicResolutionParams2.z * minFactor);
+		float maxFactor = isRight ? 2 : 1;
+		maxValue.x = 0.5 * (DynamicResolutionParams2.z * maxFactor);
+	}
 #endif
 	return clamp(screenPositionDR, minValue, maxValue);
 }
 
+float3 GetDynamicResolutionAdjustedScreenPosition(float3 screenPositionDR, uint stereo = 1)
+{
+	return float3(GetDynamicResolutionAdjustedScreenPosition(screenPositionDR.xy, stereo), screenPositionDR.z);
+}
+
 float2 GetDynamicResolutionUnadjustedScreenPosition(float2 screenPositionDR)
 {
 	return screenPositionDR * DynamicResolutionParams2.xy;
 }
 
+float3 GetDynamicResolutionUnadjustedScreenPosition(float3 screenPositionDR)
+{
+	return float3(GetDynamicResolutionUnadjustedScreenPosition(screenPositionDR.xy), screenPositionDR.z);
+}
+
 float2 GetPreviousDynamicResolutionAdjustedScreenPosition(float2 screenPosition)
 {
 	float2 screenPositionDR = DynamicResolutionParams1.zw * screenPosition;
@@ -99,3 +115,21 @@ float2 ViewToUV(float3 x, bool is_position = true, uint a_eyeIndex = 0)
 	float4 uv = mul(CameraProj[a_eyeIndex], newPosition);
 	return (uv.xy / uv.w) * float2(0.5f, -0.5f) + 0.5f;
 }
+
+/**
+ * @brief Checks if the UV coordinates are outside the frame, considering dynamic resolution if specified.
+ *
+ * This function is used to determine whether the provided UV coordinates lie outside the valid range of [0,1].
+ * If dynamic resolution is enabled, it adjusts the range according to dynamic resolution parameters.
+ *
+ * @param[in] uv The UV coordinates to check.
+ * @param[in] dynamicres Optional flag indicating whether dynamic resolution is applied. Default is false.
+ * @return True if the UV coordinates are outside the frame, false otherwise.
+ */
+bool isOutsideFrame(float2 uv, bool dynamicres = false)
+{
+	float2 max = dynamicres ? DynamicResolutionParams1.xy : float2(1, 1);
+	return any(uv < float2(0, 0) || uv > max.xy);
+}
+
+#endif  //__FRAMEBUFFER_DEPENDENCY_HLSL__

package/Shaders/Common/VR.hlsli

@@ -1,6 +1,10 @@
 #ifndef __VR_DEPENDENCY_HLSL__
 #define __VR_DEPENDENCY_HLSL__
 #ifdef VR
+#	ifndef COMPUTESHADER
+#		include "Common\Constants.hlsli"
+#		include "Common\FrameBuffer.hlsli"
+#	endif
 cbuffer VRValues : register(b13)
 {
 	float AlphaTestRefRS : packoffset(c0);
@@ -25,13 +29,26 @@ float2 ConvertToStereoUV(float2 uv, uint a_eyeIndex, uint a_invertY = 0)
 {
 #ifdef VR
 	// convert [0,1] to eye specific [0,.5] and [.5, 1] dependent on a_eyeIndex
+	uv.x = saturate(uv.x);
 	uv.x = (uv.x + (float)a_eyeIndex) / 2;
 	if (a_invertY)
 		uv.y = 1 - uv.y;
 #endif
 	return uv;
 }
 
+float3 ConvertToStereoUV(float3 uv, uint a_eyeIndex, uint a_invertY = 0)
+{
+	uv.xy = ConvertToStereoUV(uv.xy, a_eyeIndex, a_invertY);
+	return uv;
+}
+
+float4 ConvertToStereoUV(float4 uv, uint a_eyeIndex, uint a_invertY = 0)
+{
+	uv.xy = ConvertToStereoUV(uv.xy, a_eyeIndex, a_invertY);
+	return uv;
+}
+
 /**
 Converts from eye specific uv to general uv [0,1].
 In VR, texture buffers include the left and right eye in the same buffer. 
@@ -53,6 +70,18 @@ float2 ConvertFromStereoUV(float2 uv, uint a_eyeIndex, uint a_invertY = 0)
 	return uv;
 }
 
+float3 ConvertFromStereoUV(float3 uv, uint a_eyeIndex, uint a_invertY = 0)
+{
+	uv.xy = ConvertFromStereoUV(uv.xy, a_eyeIndex, a_invertY);
+	return uv;
+}
+
+float4 ConvertFromStereoUV(float4 uv, uint a_eyeIndex, uint a_invertY = 0)
+{
+	uv.xy = ConvertFromStereoUV(uv.xy, a_eyeIndex, a_invertY);
+	return uv;
+}
+
 /**
 Converts to the eye specific screenposition [0,Resolution].
 In VR, texture buffers include the left and right eye in the same buffer. Flat only has a single camera for the entire width.
@@ -66,7 +95,22 @@ This returns the adjusted value
 float2 ConvertToStereoSP(float2 screenPosition, uint a_eyeIndex, float2 a_resolution)
 {
 	screenPosition.x /= a_resolution.x;
-	return ConvertToStereoUV(screenPosition, a_eyeIndex) * a_resolution;
+	float2 stereoUV = ConvertToStereoUV(screenPosition, a_eyeIndex);
+	return stereoUV * a_resolution;
+}
+
+float3 ConvertToStereoSP(float3 screenPosition, uint a_eyeIndex, float2 a_resolution)
+{
+	float2 xy = screenPosition.xy / a_resolution;
+	xy = ConvertToStereoUV(xy, a_eyeIndex);
+	return float3(xy * a_resolution, screenPosition.z);
+}
+
+float4 ConvertToStereoSP(float4 screenPosition, uint a_eyeIndex, float2 a_resolution)
+{
+	float2 xy = screenPosition.xy / a_resolution;
+	xy = ConvertToStereoUV(xy, a_eyeIndex);
+	return float4(xy * a_resolution, screenPosition.zw);
 }
 
 #ifdef PSHADER
@@ -102,6 +146,182 @@ uint GetEyeIndexFromTexCoord(float2 texCoord)
 	return 0;
 }
 
+/**
+ * @brief Converts mono UV coordinates from one eye to the corresponding mono UV coordinates of the other eye.
+ *
+ * This function is used to transition UV coordinates from one eye's perspective to the other eye in a stereo rendering setup.
+ * It works by converting the mono UV to clip space, transforming it into view space, and then reprojecting it into the other eye's
+ * clip space before converting back to UV coordinates. It also supports dynamic resolution.
+ *
+ * @param[in] monoUV The UV coordinates and depth value (Z component) for the current eye, in the range [0,1].
+ * @param[in] eyeIndex Index of the source/current eye (0 or 1).
+ * @param[in] dynamicres Optional flag indicating whether dynamic resolution is applied. Default is false.
+ * @return UV coordinates adjusted to the other eye, with depth.
+ */
+float3 ConvertMonoUVToOtherEye(float3 monoUV, uint eyeIndex, bool dynamicres = false)
+{
+	// Convert from dynamic res to true UV space
+	if (dynamicres)
+		monoUV.xy *= DynamicResolutionParams2.xy;
+
+	// Step 1: Convert UV to Clip Space
+	float4 clipPos = float4(monoUV.xy * float2(2, -2) - float2(1, -1), monoUV.z, 1);
+
+	// Step 2: Convert Clip Space to View Space for the current eye
+	float4 viewPosCurrentEye = mul(CameraProjInverse[eyeIndex], clipPos);
+	viewPosCurrentEye /= viewPosCurrentEye.w;
+
+	// Step 3: Convert View Space to Clip Space for the other eye
+	float4 clipPosOtherEye = mul(CameraProj[1 - eyeIndex], viewPosCurrentEye);
+	clipPosOtherEye /= clipPosOtherEye.w;
+
+	// Step 4: Convert Clip Space to UV
+	float3 monoUVOtherEye = float3((clipPosOtherEye.xy * 0.5f) + 0.5f, clipPosOtherEye.z);
+
+	// Convert back to dynamic res space if necessary
+	if (dynamicres)
+		monoUVOtherEye.xy *= DynamicResolutionParams1.xy;
+
+	return monoUVOtherEye;
+}
+
+/**
+ * @brief Adjusts UV coordinates for VR stereo rendering when transitioning between eyes or handling boundary conditions.
+ *
+ * This function is used in raymarching to check the next UV coordinate. It checks if the current UV coordinates are outside
+ * the frame. If so, it transitions the UV coordinates to the other eye and adjusts them if they are within the frame of the other eye.
+ * If the UV coordinates are outside the frame of both eyes, it returns the adjusted UV coordinates for the current eye.
+ *
+ * The function ensures that the UV coordinates are correctly adjusted for stereo rendering, taking into account boundary conditions
+ * and preserving accurate reflections.  
+ * Based on concepts from https://cuteloong.github.io/publications/scssr24/
+ * Wu, X., Xu, Y., & Wang, L. (2024). Stereo-consistent Screen Space Reflection. Computer Graphics Forum, 43(4).
+ *
+ * We do not have a backface depth so we may be ray marching even though the ray is in an object.
+ 
+ * @param[in] monoUV Current UV coordinates with depth information, [0-1]. Must not be dynamic resolution adjusted.
+ * @param[in] eyeIndex Index of the current eye (0 or 1).
+ * @param[out] fromOtherEye Boolean indicating if the result UV coordinates are from the other eye.
+ *
+ * @return Adjusted UV coordinates for stereo rendering, [0-1]. Must be dynamic resolution adjusted later.
+ */
+float3 ConvertStereoRayMarchUV(float3 monoUV, uint eyeIndex, out bool fromOtherEye)
+{
+	fromOtherEye = false;
+	float3 resultUV = monoUV;
+#ifdef VR
+	// Check if the UV coordinates are outside the frame
+	if (isOutsideFrame(resultUV.xy, false)) {
+		// Transition to the other eye
+		float3 otherEyeUV = ConvertMonoUVToOtherEye(resultUV, eyeIndex);
+
+		// Check if the other eye's UV coordinates are within the frame
+		if (!isOutsideFrame(otherEyeUV.xy, false)) {
+			resultUV = ConvertToStereoUV(otherEyeUV, 1 - eyeIndex);
+			fromOtherEye = true;  // Indicate that the result is from the other eye
+		}
+	} else {
+		resultUV = ConvertToStereoUV(resultUV, eyeIndex);
+	}
+#endif
+	return resultUV;
+}
+
+/**
+ * @brief Converts stereo UV coordinates from one eye to the corresponding stereo UV coordinates of the other eye.
+ *
+ * This function is used to transition UV coordinates from one eye's perspective to the other eye in a stereo rendering setup.
+ * It works by converting the stereo UV to mono UV, then to clip space, transforming it into view space, and then reprojecting it into the other eye's
+ * clip space before converting back to stereo UV coordinates. It also supports dynamic resolution.
+ *
+ * @param[in] stereoUV The UV coordinates and depth value (Z component) for the current eye, in the range [0,1].
+ * @param[in] eyeIndex Index of the current eye (0 or 1).
+ * @param[in] dynamicres Optional flag indicating whether dynamic resolution is applied. Default is false.
+ * @return UV coordinates adjusted to the other eye, with depth.
+ */
+float3 ConvertStereoUVToOtherEyeStereoUV(float3 stereoUV, uint eyeIndex, bool dynamicres = false)
+{
+	// Convert from dynamic res to true UV space
+	if (dynamicres)
+		stereoUV.xy *= DynamicResolutionParams2.xy;
+
+	stereoUV.xy = ConvertFromStereoUV(stereoUV.xy, eyeIndex, true);  // for some reason, the uv.y needs to be inverted before conversion?
+	// Swap eyes
+	stereoUV.xyz = ConvertMonoUVToOtherEye(stereoUV.xyz, eyeIndex);
+
+	stereoUV.xy = ConvertToStereoUV(stereoUV.xy, 1 - eyeIndex, false);
+
+	// Convert back to dynamic res space if necessary
+	if (dynamicres)
+		stereoUV.xy *= DynamicResolutionParams1.xy;
+	return stereoUV;
+}
+
+/**
+ * @brief Checks if the color is non zero by testing if the color is greater than 0 by epsilon.
+ *
+ * This function check is a color is non black. It uses a small epsilon value to allow for 
+ * floating point imprecision.
+ *
+ * For screen-space reflection (SSR), this acts as a mask and checks for an invalid reflection by
+ * checking if the reflection color is essentially black (close to zero). 
+ *
+ * @param[in] ssrColor The color to check.
+ * @param[in] epsilon Small tolerance value used to determine if the color is close to zero.
+ * @return True if color is non zero, otherwise false.
+ */
+bool IsNonZeroColor(float4 ssrColor, float epsilon = 0.001)
+{
+	return dot(ssrColor.xyz, ssrColor.xyz) > epsilon * epsilon;
+}
+
+/**
+ * @brief Blends color data from two eyes based on their UV coordinates and validity.
+ *
+ * This function checks the validity of the colors based on their UV coordinates and
+ * alpha values. It blends the colors while ensuring proper handling of transparency.
+ *
+ * @param uv1 UV coordinates for the first eye.
+ * @param color1 Color from the first eye.
+ * @param uv2 UV coordinates for the second eye.
+ * @param color2 Color from the second eye.
+ * @param dynamicres Whether the uvs have dynamic resolution applied
+ * @return Blended color, including the maximum alpha from both inputs.
+ */
+float4 BlendEyeColors(
+	float3 uv1,
+	float4 color1,
+	float3 uv2,
+	float4 color2,
+	bool dynamicres = false)
+{
+	// Check validity for color1
+	bool validColor1 = IsNonZeroColor(color1) && !isOutsideFrame(uv1.xy, dynamicres);
+	// Check validity for color2
+	bool validColor2 = IsNonZeroColor(color2) && !isOutsideFrame(uv2.xy, dynamicres);
+
+	// Calculate alpha values
+	float alpha1 = validColor1 ? color1.a : 0.0f;
+	float alpha2 = validColor2 ? color2.a : 0.0f;
+
+	// Total alpha
+	float totalAlpha = alpha1 + alpha2;
+
+	// Blend based on higher alpha
+	float4 blendedColor = (validColor1 ? color1 * (alpha1 / max(totalAlpha, 1e-5)) : float4(0, 0, 0, 0)) +
+	                      (validColor2 ? color2 * (alpha2 / max(totalAlpha, 1e-5)) : float4(0, 0, 0, 0));
+
+	// Final alpha determination
+	blendedColor.a = max(color1.a, color2.a);
+
+	return blendedColor;
+}
+
+float4 BlendEyeColors(float2 uv1, float4 color1, float2 uv2, float4 color2, bool dynamicres = false)
+{
+	return BlendEyeColors(float3(uv1, 0), color1, float3(uv2, 0), color2, dynamicres);
+}
+
 struct VR_OUTPUT
 {
 	float4 VRPosition;