[vtkusers] Separating actors for different render passes

[Ken Martin]

With the render passes you can setup as many passes as you want in whatever
order you want. This shows an example where the render process is all
driven by passes.

https://gitlab.kitware.com/vtk/vtk/blob/master/Rendering/OpenGL2/Testing/Cxx/TestSobelGradientMagnitudePass.cxx

As an example for shadow maps when needed we use nested opaque passes to
render the scene from the view of the light sources which we then use in
another opaque pass to compute lighting from the view of the camera.

Render passes also have hooks that mappers call so that passes can modify
the mapper shader code etc while executing.

Passes can also use information properties on actors to filter them in
other passes.  For example an outer render pass can add information on
actors that causes some of them to not be rendered (or to be rendered
differently) by other passes ala

//
----------------------------------------------------------------------------
// Description:
// Opaque pass with key checking.
// \pre s_exists: s!=0
void vtkDefaultPass::RenderFilteredOpaqueGeometry(const vtkRenderState *s)
{
  assert("pre: s_exists" && s!=0);

  int c=s->GetPropArrayCount();
  int i=0;
  while(i<c)
  {
    vtkProp *p=s->GetPropArray()[i];
    if(p->HasKeys(s->GetRequiredKeys()))
    {
      int rendered=

p->RenderFilteredOpaqueGeometry(s->GetRenderer(),s->GetRequiredKeys());
      this->NumberOfRenderedProps+=rendered;
    }
    ++i;
  }
}




On Thu, Jul 6, 2017 at 3:30 PM, Milef, Nicholas Boris <milefn at rpi.edu>
wrote:

> Is there currently a way to separate actors into custom render passes? If
> I'm not mistaken, opaque objects currently get rendered before translucent
> objects, but is there a way to add additional geometry passes (or before
> opaque geometry, or between translucent and opaque geometry, etc.)?
>
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-- 
Ken Martin PhD
Distinguished Engineer
Kitware Inc.
28 Corporate Drive
Clifton Park NY 12065

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