> From: osg-users-boun...@lists.openscenegraph.org
> [mailto:osg-users-boun...@lists.openscenegraph.org] On Behalf Of Tueller,
> Shayne R Civ USAF AFMC 519 SMXS/MXDEC
> Sent: Tuesday, August 02, 2011 4:49 PM
> To: osg-users@lists.openscenegraph.org
> Subject: Re: [osg-users] intersection with quad mesh: only 3 verticesreturned
>
> It is true that QUAD is an OpenGL primitive but the GL driver tessellates it
> into two triangles
> underneath the hood.
>
Most (all?) cards today do break them into 2 tris, but nothing in the OpenGL
spec
says that they have to, or specifies exactly how they should do it. The reason
is
that the original SGI geometry engine did not split them. It drew quads
directly
with an odd algorithm for interpolating values across the interior. Quad lives
on
as a historical quirk, like the panda's thumb.
-Mike Garrity
-The MathWorks
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