New PostProcessRenderContext.GetScreenSpaceTemporaryRT

We need XRSettings.eyeTextureDesc to create proper single-pass temporary RTs.  But they aren't available until 2017.2.  So if there is the need to create a temporary screen space RT, there is a new function that handles the allocation.

It either uses the old explicit-argument-driven GetTemporaryRT for pre-2017.2 (monoscopic + multi-pass) or RenderTextureDescriptor 2017.2+.  There is also a 'scaler' that is applied to the texture dimensions (if needed).  I might make this more explicit in the future with explicit arguments changing the size.

Author: robbiesri

PostProcessing/Runtime/Effects/Bloom.cs

@@ -100,7 +100,7 @@ public override void Render(PostProcessRenderContext context)
 
             // Do bloom on a half-res buffer, full-res doesn't bring much and kills performances on
             // fillrate limited platforms
-            RenderTextureDescriptor pyramidDesc = context.GetDescriptor(0, context.sourceFormat);
+            var pyramidDesc = context.GetDescriptor(0, context.sourceFormat);
             pyramidDesc.width = Mathf.FloorToInt(pyramidDesc.width / (2f - rw));
             pyramidDesc.height = Mathf.FloorToInt(pyramidDesc.height / (2f - rh));
 

PostProcessing/Runtime/Effects/DepthOfField.cs

@@ -124,10 +124,10 @@ public override void Render(PostProcessRenderContext context)
                 cocFormat = SelectFormat(RenderTextureFormat.RHalf, RenderTextureFormat.Default);
             #endif
 
-            RenderTextureDescriptor colorDesc = context.GetDescriptor(0, colorFormat);
+            var colorDesc = context.GetDescriptor(0, colorFormat);
             colorDesc.width /= 2;
             colorDesc.height /= 2;
-            RenderTextureDescriptor cocDesc = context.GetDescriptor(0, cocFormat, RenderTextureReadWrite.Linear);
+            var cocDesc = context.GetDescriptor(0, cocFormat, RenderTextureReadWrite.Linear);
 
             // Material setup
             var f = settings.focalLength.value / 1000f;

PostProcessing/Runtime/PostProcessRenderContext.cs

@@ -26,14 +26,18 @@ public Camera camera
                 if (XRSettings.isDeviceActive)
                 {
 #if UNITY_2017_2_OR_NEWER
-                    RenderTextureDescriptor xrDesc = XRSettings.eyeTextureDesc;
+                    var xrDesc = XRSettings.eyeTextureDesc;
                     width = xrDesc.width;
                     height = xrDesc.height;
                     m_sourceDescriptor = xrDesc;
 #else
-                    width = XRSettings.eyeTextureWidth; // double this for single-pass when we can't query eyeTextureDesc
+                    // Single-pass is only supported with 2017.2+ because
+                    // that is when XRSettings.eyeTextureDesc is available.
+                    // Without it, we don't have a robust method of determining
+                    // if we are in single-pass.  Users can just double the width
+                    // here if they KNOW they are using single-pass.
+                    width = XRSettings.eyeTextureWidth;
                     height = XRSettings.eyeTextureHeight;
-                    // TODO: fill in m_sourceDescriptor
 #endif
 
                     if (camera.stereoActiveEye == Camera.MonoOrStereoscopicEye.Right)
@@ -47,9 +51,10 @@ public Camera camera
                     width = m_Camera.pixelWidth;
                     height = m_Camera.pixelHeight;
 
+#if UNITY_2017_2_OR_NEWER
                     m_sourceDescriptor.width = width;
                     m_sourceDescriptor.height = height;
-
+#endif
                     xrSingleEyeWidth = width;
                     xrSingleEyeHeight = height;
                 }
@@ -97,10 +102,11 @@ public Camera camera
         // Current camera height in pixels
         public int height { get; private set; }
 
+#if UNITY_2017_2_OR_NEWER
         private RenderTextureDescriptor m_sourceDescriptor;
         public RenderTextureDescriptor GetDescriptor(int depthBufferBits = 0, RenderTextureFormat colorFormat = RenderTextureFormat.Default, RenderTextureReadWrite readWrite = RenderTextureReadWrite.Default)
         {
-            RenderTextureDescriptor modifiedDesc = new RenderTextureDescriptor(m_sourceDescriptor.width, m_sourceDescriptor.height, 
+            var modifiedDesc = new RenderTextureDescriptor(m_sourceDescriptor.width, m_sourceDescriptor.height, 
                                                                                 m_sourceDescriptor.colorFormat, depthBufferBits);
             modifiedDesc.dimension = m_sourceDescriptor.dimension;
             modifiedDesc.volumeDepth = m_sourceDescriptor.volumeDepth;
@@ -120,6 +126,24 @@ public RenderTextureDescriptor GetDescriptor(int depthBufferBits = 0, RenderText
 
             return modifiedDesc;
         }
+#endif
+
+        public void GetScreenSpaceTemporaryRT(CommandBuffer cmd, int nameID, 
+                                            int depthBufferBits = 0, RenderTextureFormat colorFormat = RenderTextureFormat.Default, RenderTextureReadWrite readWrite = RenderTextureReadWrite.Default,
+                                            FilterMode filter = FilterMode.Bilinear, int dimScaler = 1)
+        {
+#if UNITY_2017_2_OR_NEWER
+            var desc = GetDescriptor(depthBufferBits, colorFormat, readWrite);
+            desc.width /= dimScaler;
+            desc.height /= dimScaler;
+            cmd.GetTemporaryRT(nameID, desc, filter);
+#else
+            int actualWidth = width / dimScaler;
+            int actualHeight = height / dimScaler;
+            cmd.GetTemporaryRT(nameID, width, height, depthBufferBits, filter, colorFormat, readWrite);
+            // TODO: How to handle MSAA for XR in older versions?  Query cam?      
+#endif
+        }
 
         // Current active rendering eye (for XR)
         public int xrActiveEye { get; private set; }
@@ -146,7 +170,9 @@ public void Reset()
             width = 0;
             height = 0;
 
+#if UNITY_2017_2_OR_NEWER
             m_sourceDescriptor = new RenderTextureDescriptor(0, 0);
+#endif
 
             xrActiveEye = (int)Camera.StereoscopicEye.Left;
             xrSingleEyeWidth = 0;