[vtk-developers] vtkOpenGLPolyDataMapper::RenderPiece

[Miller, James V (CRD)]

I believe all the MakeCurrent calls query to see if the current context matches the render window.
If it matches, then glMakeCurrent is not called. We are assuming here that determining which context
is current is lightweight in comparison to actually switching the context. From your test results,
however, it looks as though just querying which context is current takes 50% longer than all the call
lists (?), i.e. asking what the current context is is a pretty heavyweight call.

Sounds like the only solution is to keep a global on what context is current and mutex around it (in
case multiple threads are active). I wonder if VTK should have a "thread" object that gets pushed
through the rendering system.  Then the rendering system could query the thread object as to what the
current context for the that thread is.



-----Original Message-----
From: Mark Beall [mailto:mbeall2 at simmetrix.com]
Sent: Tuesday, May 29, 2001 11:42 AM
To: vtkdev
Subject: Re: [vtk-developers] vtkOpenGLPolyDataMapper::RenderPiece


Hi Lisa,
This is important with respect to our little quest to get good
rendering speed with a large number of actors. In our test all
these calls to MakeCurrent take 50% longer than all the calls
to glCallList, so we would like to eliminate them. 

mark

On 5/29/01 9:50 AM Lisa S. Avila (lisa.avila at kitware.com) wrote:

>Hi Bob,
>
>MakeCurrent must be called any time the window may have become uncurrent 
>(for want of a better term!) This can happen unexpectedly - and I actually 
>spent many hours on several problems tracking it down to an uncurrent window.
>
>During the rendering process a prop may update, causing its mapper to 
>update. The mapper may get data that is pulled from another window - 
>causing that other window to become current. Or, a start / end method on 
>some filter may have a render call into another window (as is done with the 
>pipeline viewer)
>
>If you think this is a serious issue, we can start keeping "global" state 
>information in the render window. You'll still make the 120,000 calls, but 
>they will simply check the current state and return if no MakeCurrent is 
>actually necessary.
>
>Lisa
>
>
>At 02:55 PM 5/25/2001, obara wrote:
>>Hi Folks,
>>
>>Doesn't vtkOpenGlRenderWindow::MakeCurrent() only have to be called once
>>when rendering the window?  We were rendering a simple scene 120x's and
>>found this function being called 120,000 because
>>vtkOpenGLPolyDataMapper::RenderPiece() calls
>>vtkOpenGlRenderWindow::MakeCurrent().
>>
>>At least I didn't ask anything about indentation or where to put braces.
>>
>>Thanks in advance,
>>
>>Bob
>>
>>Robert M. O'Bara
>>Senior Software Engineer
>>Simmetrix Inc.
>>1223 Peoples Ave.
>>Troy, NY 12180
>>
>>Lab: (518) 276-2867
>>Main Office: (518) 276-2729
>>
>>
>>
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>
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