Avoid using the same cache variable for different passes

The cache variable LastWindowSize was used for checking whether
RenderToImage FBO needs to be updated as well as for checking
whether DepthPass FBO needs to be updated. If both the modes were
used together, the depth pass updates the cache value and never
lets RenderToImage mode update its FBO.

Rendering/VolumeOpenGL2/vtkOpenGLGPUVolumeRayCastMapper.cxx

@@ -116,7 +116,9 @@ class vtkOpenGLGPUVolumeRayCastMapper::vtkInternal
     this->TextureSize[0] = this->TextureSize[1] = this->TextureSize[2] = -1;
     this->WindowLowerLeft[0] = this->WindowLowerLeft[1] = 0;
     this->WindowSize[0] = this->WindowSize[1] = 0;
-    this->LastWindowSize[0] = this->LastWindowSize[1] = 0;
+    this->LastDepthPassWindowSize[0] = this->LastDepthPassWindowSize[1] = 0;
+    this->LastRenderToImageWindowSize[0] = 0;
+    this->LastRenderToImageWindowSize[1] = 0;
     this->ScalarsRange[0][0] = this->ScalarsRange[0][1] = 0.0;
     this->ScalarsRange[1][0] = this->ScalarsRange[1][1] = 0.0;
     this->ScalarsRange[2][0] = this->ScalarsRange[2][1] = 0.0;
@@ -382,7 +384,8 @@ class vtkOpenGLGPUVolumeRayCastMapper::vtkInternal
   int TextureSize[3];
   int WindowLowerLeft[2];
   int WindowSize[2];
-  int LastWindowSize[2];
+  int LastDepthPassWindowSize[2];
+  int LastRenderToImageWindowSize[2];
 
   double ScalarsRange[4][2];
   double LoadedBounds[6];
@@ -2214,11 +2217,11 @@ void vtkOpenGLGPUVolumeRayCastMapper::vtkInternal::SetupRenderToTexture(
 {
   if (this->Parent->RenderToImage && this->Parent->CurrentPass == RenderPass)
     {
-    if ( (this->LastWindowSize[0] != this->WindowSize[0]) ||
-         (this->LastWindowSize[1] != this->WindowSize[1]) )
+    if ( (this->LastRenderToImageWindowSize[0] != this->WindowSize[0]) ||
+         (this->LastRenderToImageWindowSize[1] != this->WindowSize[1]) )
       {
-      this->LastWindowSize[0] = this->WindowSize[0];
-      this->LastWindowSize[1] = this->WindowSize[1];
+      this->LastRenderToImageWindowSize[0] = this->WindowSize[0];
+      this->LastRenderToImageWindowSize[1] = this->WindowSize[1];
       this->ReleaseRenderToTextureGraphicsResources(ren->GetRenderWindow());
       }
 
@@ -2342,11 +2345,11 @@ void vtkOpenGLGPUVolumeRayCastMapper::vtkInternal::ExitRenderToTexture(
 void vtkOpenGLGPUVolumeRayCastMapper::vtkInternal::SetupDepthPass(
   vtkRenderer* ren)
 {
-  if ( (this->LastWindowSize[0] != this->WindowSize[0]) ||
-       (this->LastWindowSize[1] != this->WindowSize[1]) )
+  if ( (this->LastDepthPassWindowSize[0] != this->WindowSize[0]) ||
+       (this->LastDepthPassWindowSize[1] != this->WindowSize[1]) )
     {
-    this->LastWindowSize[0] = this->WindowSize[0];
-    this->LastWindowSize[1] = this->WindowSize[1];
+    this->LastDepthPassWindowSize[0] = this->WindowSize[0];
+    this->LastDepthPassWindowSize[1] = this->WindowSize[1];
     this->ReleaseDepthPassGraphicsResources(ren->GetRenderWindow());
     }