feat: add VR water shader

package/Shaders/Common/VR.hlsl

@@ -1,35 +1,58 @@
 /**
-Converts to the eye specific uv.
-In VR, texture buffers include the left and right eye in the same buffer. Flat only has a single camera for the entire width.
-This means the x value [0, .5] represents the left eye, and the y value (.5, 1] are the right eye.
-This returns the adjusted value
+Converts to the eye specific uv [0,1].
+In VR, texture buffers include the left and right eye in the same buffer. Flat
+only has a single camera for the entire width. This means the x value [0, .5]
+represents the left eye, and the x value (.5, 1] are the right eye. This returns
+the adjusted value
 @param uv - uv coords [0,1] to be encoded for VR
 @param a_eyeIndex The eyeIndex; 0 is left, 1 is right
+@param a_invertY Whether to invert the Y direction
 @returns uv with x coords adjusted for the VR texture buffer
 */
-float2 ConvertToStereoUV(float2 uv, uint a_eyeIndex)
+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 = (uv.x + (float)a_eyeIndex) / 2;
+	if (a_invertY)
+		uv.y = 1 - uv.y;
 #endif
 	return uv;
 }
 
 /**
-Converts from eye specific uv to general 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. 
-This means the x value [0, .5] represents the left eye, and the y value (.5, 1] are the right eye.
+This means the x value [0, .5] represents the left eye, and the x value (.5, 1] are the right eye.
 This returns the adjusted value
 @param uv - eye specific uv coords [0,1]; if uv.x < 0.5, it's a left eye; otherwise right
 @param a_eyeIndex The eyeIndex; 0 is left, 1 is right
+@param a_invertY Whether to invert the Y direction
 @returns uv with x coords adjusted to full range for either left or right eye
 */
-float2 ConvertFromStereoUV(float2 uv, uint a_eyeIndex)
+float2 ConvertFromStereoUV(float2 uv, uint a_eyeIndex, uint a_invertY = 0)
 {
 #ifdef VR
 	// convert [0,.5] to [0, 1] and [.5, 1] to [0,1]
 	uv.x = 2 * uv.x - (float)a_eyeIndex;
+	if (a_invertY)
+		uv.y = 1 - uv.y;
 #endif
 	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.
+This means the x value [0, resx/2] represents the left eye, and the x value (resx/2, x] are the right eye.
+This returns the adjusted value
+@param screenPosition - Screenposition coords ([0,resx], [0,resy]) to be encoded for VR
+@param a_eyeIndex The eyeIndex; 0 is left, 1 is right
+@param a_resolution The resolution of the screen
+@returns screenPosition with x coords adjusted for the VR texture buffer
+*/
+float2 ConvertToStereoSP(float2 screenPosition, uint a_eyeIndex, float2 a_resolution)
+{
+	screenPosition.x /= a_resolution.x;
+	return ConvertToStereoUV(screenPosition, a_eyeIndex) * a_resolution;
+}