[vtkusers] drawing very quickly in an overlay (tracking mouse with a line)

[Malcolm Drummond]

Hi John

Thanks very much for the advice. Unfortunately I can't rely on decent texture mapping. Many of the users have machines that can only be described as a form of punishment. I've had to keep the visualization pretty basic, but all that is required anyway is to choose parts of a broken up surface to be fitted to planes so they can run a simplified model.

I tried your idea anyway, even just using an image actor (no textures) comes out all wrong on their machines - though it looks right on mine. I know many of the users have old ATI chips, which I've had problems with before. Ironically on the machines that could handle your trick, the straightforward rendering is pretty quick anyway.

In the worst case I could continue to do all the transformations with VTK and then paint on my own canvas, do a bitblt and draw the latest polygon segment with XOR.

Any other suggestions?

Thanks
Malcolm 
  ----- Original Message ----- 
  From: John Biddiscombe 
  To: Malcolm Drummond ; vtkusers 
  Sent: Wednesday, September 24, 2003 11:26 AM
  Subject: RE: [vtkusers] drawing very quickly in an overlay (tracking mouse with a line)


  You'll have to actually capture the back buffer and redisplay it, turning on and off backing store won't circumvent the pipeline re-execution which is your trouble.

  Nifty tip : Try capturing the original window using renderwindow->image, then generate a texture from it. then display the texture as the full image in your polygon window and overlay your polylines on that. Quick updates, no trouble.

  JB

    -----Original Message-----
    From: Malcolm Drummond [mailto:malcolm at geovision.co.za]
    Sent: 24 September 2003 08:31
    To: vtkusers
    Subject: [vtkusers] drawing very quickly in an overlay (tracking mouse with a line)


    Hi

    Can anyone offer advice on drawing very quickly in an overlay?

    I have a companion '2D' window which basically renders a 3D parallel projection that has been transformed by the camera matrix from the main '3D' window. In the second window the user creates fence polygons around regions of interest with a mouse - after which I do point-in-polygon stuff etc. So far so good - however on large datasets the rendering of the polygon segment lags way behind the mouse position.

    I draw the most recent segment of the fence polygon (ie. the one that is tracking the mouse) in an overlay layer in the hope that I could use backing store on the background renderer, but I'm not seeing any real difference in performance. Maybe I'm not using backing store correctly - I switch backing store on when I start catching mouse events for the polygons, switch off when I have the whole polygon, but all the rendering in-between seems to be refreshing both renderers.

    Has anyone experience with this?  

    Thanks
    Malcolm Drummond
    GeoVision cc
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