Re: Clipping with arbitary planes

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Angus Dorbie (dorbie++at++bitch.reading.sgi.com)
Fri, 21 Mar 1997 01:20:21 +0000

You can call glClipPlane and glEnable from within a performer draw
callback.

This will allow you to create an arbitrary clip plane which slices
through the scene.

The other problem is then, how do you cap the end of the clipped
geometry so that it looks like you've sliced through an object.

This is a little trickier but the sort of thing you can easily implement
is disabling backface culling, ie pfCullFace(PFCF_OFF) and have a back
facing material which is black with a two sided lighting model applied.

This should give you a slice through the database.

There are a number tricks involving stencil plane operations and
multiple/separate passes on the back & front facing geometry to draw
a capping surface with texrure & lighting which you may want to
consider once you have implemented the simple clipping outlined
above.

Cheers,Angus.

On Mar 20, 2:51pm, Jukka Vaisanen wrote:
> Subject: Clipping with arbitary planes
>
>
> I am creating a model viewer with Performer which will be used by artists
> creating content for mostly entertainment applications. It is part of a
> toolset for a cross-platform 3D engine used by major game developers.
>
> What I would like to do is create a cross-section of the model, a bit like
> if I set the near clipping plane too far. But I would like to clip the
> model with arbitarily placed planes (or even better, cubes). The solidview
> demo does this. I'm kinda lost on where to start with Performer.
>
>
>
> Jukka Vaisanen
>
> Iscape Software vaizki++at++iscape.fi
> Tel: +358-9-648686 GSM: +358-40-5007978
>
> =======================================================================
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>-- End of excerpt from Jukka Vaisanen

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