vtkOpenGLProjectedTetrahedraMapper: move shader binding

Move binding of the shader program needed for the projected
tetrahedra rendering algorithm closer to where it is needed.
This makes it less likely to interfere with other shader
programs that may be used in the algorithm.

Rendering/VolumeOpenGL2/vtkOpenGLProjectedTetrahedraMapper.cxx

@@ -338,32 +338,6 @@ void vtkOpenGLProjectedTetrahedraMapper::Render(vtkRenderer* renderer, vtkVolume
   vtkUnstructuredGridBase* input = this->GetInput();
   vtkVolumeProperty* property = volume->GetProperty();
 
-  // has something changed that would require us to recreate the shader?
-  if (!this->Tris.Program)
-  {
-    // build the shader source code
-    std::string VSSource = vtkglProjectedTetrahedraVS;
-    std::string FSSource = vtkglProjectedTetrahedraFS;
-    std::string GSSource;
-
-    // compile and bind it if needed
-    vtkShaderProgram* newShader = renWin->GetShaderCache()->ReadyShaderProgram(
-      VSSource.c_str(), FSSource.c_str(), GSSource.c_str());
-
-    // if the shader changed reinitialize the VAO
-    if (newShader != this->Tris.Program)
-    {
-      this->Tris.Program = newShader;
-      this->Tris.VAO->ShaderProgramChanged(); // reset the VAO as the shader has changed
-    }
-
-    this->Tris.ShaderSourceTime.Modified();
-  }
-  else
-  {
-    renWin->GetShaderCache()->ReadyShaderProgram(this->Tris.Program);
-  }
-
   // Check to see if input changed.
   if ((this->InputAnalyzedTime < this->MTime) || (this->InputAnalyzedTime < input->GetMTime()))
   {
@@ -548,6 +522,32 @@ void vtkOpenGLProjectedTetrahedraMapper::ProjectTetrahedra(
     vtkOpenGLCheckErrorMacro("failed at glBlitFramebuffer");
   }
 
+  // has something changed that would require us to recreate the shader?
+  if (!this->Tris.Program)
+  {
+    // build the shader source code
+    std::string VSSource = vtkglProjectedTetrahedraVS;
+    std::string FSSource = vtkglProjectedTetrahedraFS;
+    std::string GSSource;
+
+    // compile and bind it if needed
+    vtkShaderProgram* newShader = window->GetShaderCache()->ReadyShaderProgram(
+      VSSource.c_str(), FSSource.c_str(), GSSource.c_str());
+
+    // if the shader changed reinitialize the VAO
+    if (newShader != this->Tris.Program)
+    {
+      this->Tris.Program = newShader;
+      this->Tris.VAO->ShaderProgramChanged(); // reset the VAO as the shader has changed
+    }
+
+    this->Tris.ShaderSourceTime.Modified();
+  }
+  else
+  {
+    window->GetShaderCache()->ReadyShaderProgram(this->Tris.Program);
+  }
+
   // TODO:
   // There are some caching optimizations that could be used
   // here to skip various expensive operations (eg sorting