Re: Virtual cliptexture problems

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Jan Barglowski (jan++at++archimedes.vislab.navy.mil)
Mon, 4 May 1998 11:48:59 -0700 (PDT)


Jonas Andersson wrote:
> I am using the pfdloader to load a geometry which geostate I then switch
> to a new one containing a cliptexture. This works fine.
>
> Problem 1:
> Is it possible to save scene-graphs containing cliptextures to any format?
> My attempts to save the created scenegraph fails; the .pfb
> file is created but it do not contain neither geometry or cliptexture.
> When saving I get the following warning:

Unfortunately, cliptextures can't be saved to a .pfb file. I think
(not sure) it may have something to do with the texgen matrix. Hopefully
this can be implemented in the next version of Performer?
  
> Problem 2:
> How can I get rid of the following effect?
> When using cliptextures larger then 32768*32768, e.g. virtual
> cliptextures, the cliptexture gets distorted. It looks like only a fourth
> of the cliptexture (centered around the clipcenter as it changes) can
> be displayed correctly. The rest of the cliptexture looks like when
> trying to repeat a texture with CLAMPING OFF.

> The same cliptexture looks OK when viewed using the .ct-loader.

Of course, you know that if you're using larger than 32k cliptextures,
you must manage the LODOffset yourself! The .ct loader automatically
deals with virtual cliptextures by adjusting the LODOffset for each
concentric "ring" of geometry (turn on wireframe and see). To see if
this is your problem, turn on the "Offset" button from Auto to "="
and you should see some serious smearing on the cliptexture.

For a good explanation of how to manage virtual cliptexture, see the
Performer manual, plus virtcliptexture.c and the .ct loader. I
have developed a technique for using .flt terrains and virtual
cliptextures if you need it.

jan

-- 
Jan Anthony Barglowski	              jan++at++chinalake.navy.mil
Real-time Computer Graphics           http://www1.ridgecrest.ca.us/~jan
Naval Air Warfare Center, China Lake  (760) 927-1057
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