RE: [Algorithms] Polygon clipping

[Brian M. <bma...@ra...>]

	Different from the normal. I was assuming that the fan was for a convex
polygon. DOH! For a convex polygon the vertices are in fan order anyway and
remain so after clipping. This example is not convex so I guess you could
use more general polygon clipping. Sutherland-Hodgham will clip concave
polygons, in this case giving 2 polygons out, or a degenerate triangle (zero
area) connecting the 2 fragments. There is some info on this in FvD etc.
	If your generating the strips/fans offline it may be worthwhile only
allowing convex fans - you'd have to time the benefits of bigger fans
against more complex clipping code.

-Brian.

> -----Original Message-----
> From: gda...@li...
> [mailto:gda...@li...]On Behalf Of Klaus
> Hartmann
> Sent: Wednesday, July 26, 2000 1:25 PM
> To: gda...@li...
> Subject: Re: [Algorithms] Polygon clipping
>
>
> Tom, and Brian.... thanks for your help.
>
> I realize now, that this becomes API-specific, so I'm going to move this
> thread over to some D3D group, because I still have some questions.
>
> There's just one thing I'd like to mention here...
>
> ----- Original Message -----
> From: Tom Forsyth <to...@mu...>
> To: <gda...@li...>
>
> > Fans remain fans (though it may be knarly to find the ordering), strips
> > don't - they can become multiple strips (think about a U-shaped strip
> where
> > the bottom of the U is off-screen).
>
> Your U-shape example, tells me, that I can also get multiple fans. Have a
> look at the following image that shows a V-shaped fan:
> http://www.thecore.de/TheCore/fan.jpg
>
>
> Thanks,
> Niki
>
>
>
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