[vtkusers] Question to performance leak in multipass Rendering in VTK

[Rocco Gasteiger]

Dear VTK users,

 

I derived my own render pass class from vtkRenderPass and want to perform
two render passes in it. My scene consists of two objects A and B. For each
object, I want to store its depth values in a depth texture by using frame
buffer objects (fbo). For accomplishing this task, I call two times
"this->DelegatePass->Render(&myRenderState)" within my derived rendering
class. My delegate rendering pass is a vtkDefaultPass. For rendering A I set
opacity of B to zero and for object B I do it the same for A. Here is a
pseudo code snippet of what I have done. 

 

void vtkMyRenderPass::Render()

{

                // Perform some tests

                // .

                // Create fbo and render state

                // Get actor for object B

                actorB->SetOpacity(0.0)

 

                // Create first depth texture and assign it to fbo

                // Perform first render pass

                this->DelegatePass->Render(&newRenderState);

                

                // Reset opacity of actorB           

 

// Get actor for object A

                actorA->SetOpacity(0.0)

 

 

                // Create second depth texture and assign it to fbo

// Perform second render pass 

this->DelegatePass->Render(&newRenderState);

 

// Reset opacity of actorA           

}

 

It works fine so far. But I notice a strong performance leak during
interaction due to the second offscreen rendering. Can anybody give me a
hint what the reason for this is? My render window is 300x300 and I use a
GeForce 9800 GT. Do I have to write a separate render pass class for each
render pass and collect them in a vtkRenderPassCollection (e.g.
vtkMyRenderPassA and vtkMyRenderPassB, for object A and B)?

 

Many thanks in advance and best regards,

Rocco Gasteiger

 

 

 

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