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<div class=Section1>
<p class=MsoNormal>Dear VTK-Users,<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span lang=EN-US>in a previous post (<a
href="http://www.vtk.org/pipermail/vtkusers/2009-December/104490.html">http://www.vtk.org/pipermail/vtkusers/2009-December/104490.html</a>)
I reported a strong performance leak during rendering twice of my object with
the new multipass framework of VTK. Especially, if my object consist of many
triangles. Now, I figured out what the problem was by examine the source code
of the vtkOpenGLMapper and want to shade these information with the
VTK-community, especially these users which have not yet a deep understanding
of the rendering pipeline of VTK, like me.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>In the render-routine of my derived
vtkRenderPass-class I changed some actor properties, e.g., surface rendering
style (wireframe or surface) or opacity via “actor->GetProperty()->SetOpacity(…)”
in each pass. This occurred a deletion and new creation of the display lists of
the corresponding polydata-object in the mapper. Because this happened every
frame, the performance leak occurred.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>To resolve it, I use the property key
capability of the frame work by orientation to vtkShadowMappPass. Like in my previous
approach, I create different actors of my object based on the same vtkPolyData
object. After this, I set the properties of each actor in that way I want to
use it in the corresponding pass (e.g. wireframe). Additionally I set different
vtkInformation-objects with special keys as property keys to the actors. In my
render-routine of my derived vtkRenderingPass I set the required keys to my
render state object and only these actor(s) with the same key is (are) rendered.
Now I can call <o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'>this->DelegatePass->Render(&newRenderState);
multiple times with setting the correct key property and without performace
leak.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'>Here
is a (pseudo-)code snippet which illustrate what I have done. For
simplification I distinguish between my main-routine (definition of the
vtkPolyData, vtkRenderer and so on) and my derived vtkRenderPass-class
vtkMyRenderPass.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>///////////////<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>Main-routine:<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>///////////////<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>// 1. Setup actors with corresponding key
properties<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New";
color:#010001'>mySurfaceMapper->SetInput(myVtkPolyData);<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New";
color:#010001'>mySurfaceActor->SetMapper(mySurfaceMapper);<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New";
color:#010001'>myWireframeSurfaceActor->SetMapper(mySurfaceMapper);<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span lang=EN-US
style='font-size:10.0pt;font-family:"Courier New";color:#010001'>vtkSmartPointer</span><span
lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'><<span
style='color:#010001'>vtkInformation</span>><span style='color:#010001'>surfacePropKey</span>
= <span style='color:#010001'>vtkSmartPointer</span><<span style='color:
#010001'>vtkInformation</span>>::<span style='color:#010001'>New</span>();<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span lang=EN-US
style='font-size:10.0pt;font-family:"Courier New";color:#010001'>surfacePropKey</span><span
lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> -><span
style='color:#010001'>Set</span>(<span style='color:#010001'>vtkMyRenderPass</span>::<span
style='color:#010001'>SURFACE</span>(), 0);<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span lang=EN-US
style='font-size:10.0pt;font-family:"Courier New";color:#010001'>surfaceActor</span><span
lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'>-><span
style='color:#010001'>SetPropertyKeys</span>(<span style='color:#010001'>surfacePropKey</span>);<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span lang=EN-US
style='font-size:10.0pt;font-family:"Courier New";color:#010001'>vtkSmartPointer</span><span
lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'><<span
style='color:#010001'>vtkInformation</span>>wirfeframe<span
style='color:#010001'>PropKey</span> = <span style='color:#010001'>vtkSmartPointer</span><<span
style='color:#010001'>vtkInformation</span>>::<span style='color:#010001'>New</span>();<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span lang=EN-US
style='font-size:10.0pt;font-family:"Courier New"'>wirfeframe<span
style='color:#010001'>PropKey</span> -><span style='color:#010001'>Set</span>(<span
style='color:#010001'>vtkMyRenderPass</span>::WIREFRAME(), 0);<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span lang=EN-US
style='font-size:10.0pt;font-family:"Courier New";color:#010001'>myWireframeSurfaceActor->SetPropertyKeys</span><span
lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'>(wirfeframe<span
style='color:#010001'>PropKey</span>);<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>// 2. Create all necessary passes (vtkLightsPass,
vtkOpaquePass, vtkTranslucentPass, and so on), collect them<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>// in a vtkRenderPassCollection, pass it into
a vtkSequencePass and delegate it to a vtkCameraPass.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>// 3. Create vtkMyRenderPass and set its delegate
pass to the vtkCameraPass.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New";
color:#010001'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>////////////////////</span><span
lang=EN-US style='font-size:10.0pt;font-family:"Courier New";color:#010001'><o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New";
color:#010001'>vtkMyRenderPass<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>////////////////////<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>// 1. Setup pass like other rendering
passes e.g. vtkShadowMappPass (e.g. frame buffers, texture objects, shaders, …)<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>// 2. Define the property keys in the
header file …<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New";
color:#010001'>static vtkInformationIntegerKey *SURFACE();<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New";
color:#010001'>static vtkInformationIntegerKey *WIREFRAME ();<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>// …and the corresponding macros in
the c++-file<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New";
color:#010001'>vtkInformationKeyMacro</span><span style='font-size:10.0pt;
font-family:"Courier New"'>(</span><span lang=EN-US style='font-size:10.0pt;
font-family:"Courier New";color:#010001'>vtkMyRenderPass</span><span
style='font-size:10.0pt;font-family:"Courier New"'>,<span style='color:#010001'>SURFACE</span>,<span
style='color:#010001'>Integer</span>);<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New";
color:#010001'>vtkInformationKeyMacro</span><span style='font-size:10.0pt;
font-family:"Courier New"'>(</span><span lang=EN-US style='font-size:10.0pt;
font-family:"Courier New";color:#010001'>vtkMyRenderPass</span><span
style='font-size:10.0pt;font-family:"Courier New"'>,</span><span
style='font-size:10.0pt;font-family:"Courier New"'> <span lang=EN-US>WIREFRAME</span></span><span
style='font-size:10.0pt;font-family:"Courier New"'>,<span style='color:#010001'>Integer</span>);<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>// 3. Create vtkInformation-object which
holds the current required keys<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span lang=EN-US
style='font-size:10.0pt;font-family:"Courier New";color:#010001'>if (this->requiredKeys
== 0) this->requiredKeys = vtkSmartPointer<vtkInformation>::New();<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New";
color:#010001'>this->requiredKeys</span><span lang=EN-US style='font-size:
10.0pt;font-family:"Courier New"'>-><span style='color:#010001'>Set</span>(<span
style='color:#010001'>vtkMyRenderPass</span>::<span style='color:#010001'>SURFACE</span>(),0);<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New";
color:#010001'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>// 4. Create vtkRenderState object, set
key-object, framebuffers and so on<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span lang=EN-US
style='font-size:10.0pt;font-family:"Courier New";color:#010001'>vtkRenderState</span><span
lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'> <span
style='color:#010001'>newRenderState</span>(<span style='color:#010001'>renderer</span>);<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span lang=EN-US
style='font-size:10.0pt;font-family:"Courier New";color:#010001'>newRenderState</span><span
lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'>.<span
style='color:#010001'>SetPropArrayAndCount</span>(<span style='color:#010001'>renderState</span>-><span
style='color:#010001'>GetPropArray</span>(), <span style='color:#010001'>renderState</span>-><span
style='color:#010001'>GetPropArrayCount</span>());<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New";
color:#010001'>newRenderState</span><span lang=EN-US style='font-size:10.0pt;
font-family:"Courier New"'>.<span style='color:#010001'>SetRequiredKeys</span>(<span
style='color:#010001'>requiredKeys</span>);<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New";
color:#010001'>newRenderState.SetFrameBuffer(this->FrameBufferObject);<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>// 5. Render first pass<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New";
color:#010001'>this->DelegatePass->Render(renderState);<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New";
color:#010001'>this->NumberOfRenderedProps += this->DelegatePass->GetNumberOfRenderedProps();<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>// 6. Remove key SURFACE and set key
WIREFRAME <o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span lang=EN-US
style='font-size:10.0pt;font-family:"Courier New";color:#010001'>requiredKeys</span><span
lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'>-><span
style='color:#010001'>Remove</span>(<span style='color:#010001'>vtkHiddenLineDesignerPass</span>::<span
style='color:#010001'>SURFACE_SEMI</span>());<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New";
color:#010001'>requiredKeys</span><span lang=EN-US style='font-size:10.0pt;
font-family:"Courier New"'>-><span style='color:#010001'>Set</span>(<span
style='color:#010001'>vtkMyRenderPass</span>::WIREFRAME(),0);<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span lang=EN-US
style='font-size:10.0pt;font-family:"Courier New";color:#010001'>newRenderState</span><span
lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'>.<span
style='color:#010001'>SetRequiredKeys</span>(<span style='color:#010001'>requiredKeys</span>);<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span lang=EN-US
style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>// 7. Render second pass<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New";
color:#010001'>this->DelegatePass->Render(renderState);<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New";
color:#010001'>this->NumberOfRenderedProps += this->DelegatePass->GetNumberOfRenderedProps();<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>// 8. Remove key WIREFRAME to have a “clean”
key-property object for a new call of the render-routine<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New";
color:#010001'>requiredKeys</span><span lang=EN-US style='font-size:10.0pt;
font-family:"Courier New"'>-><span style='color:#010001'>Remove</span>(<span
style='color:#010001'>vtkMyRenderPass</span>:: WIREFRAME());<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New";
color:#010001'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>I hope this small example helps somebody by
implementing its on multipass algorithms. The capability of the key property
object is a very flexible and good design decision . Thanks to </span><span
lang=EN-US>François Bertel for designing and implementing this framework!<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>Best regards, Rocco</span><span lang=EN-US><o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
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