The software approach you describe is along the lines of what I'm looking
for- I've tried something similar to the "hardware" approach you describe,
and it results in the distortions others mentioned.

For obtaining the contour in software, wouldn't getting the points where the
distance of the vertices from the cutting plane is equal to zero essentially
leave you with gaps, where vertices don't fall on the plane?  You could
apply a fudge factor, but then you'd end up with distortions.

-Ed


-----Original Message-----
From: Raj N. Vaidya [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, October 09, 2002 8:12 AM
To: [EMAIL PROTECTED]
Subject: Re: [JAVA3D] Drawing intersection of Geometry with Cutting
Plane


Well, a couple of ways that I could think of....

In software, you can generate a contour line through the elements of
your GeometryArray - tris/quads. The contour line is the locus of points
where the signed normal distance of the vertices from the cutting plane
is equal to zero. In the case of a sphere, you will get a circle - possibly
a great circle depending upon where you cut the sphere.

In "hardware", I think you may be able to use 2 appropriately
oriented parallel ModelClip planes to achieve the effect. This would
produce a ring actually, but if the distance between the clip planes is
small enough it will look like a line contour. Haven't tried it,
but looks like it would work.


Regards

Vaidya


>On Wed, 9 Oct 2002 07:50:48 -0700, Scholl, Ed <[EMAIL PROTECTED]> wrote:

>Hello-
>Can anyone give me some pointers to draw the 2D outline obtained from the
>intersection of a cutting plane with my 3D world?  i.e. if I specify a
>cutting plane that intersects with a sphere, I want to display the
resulting
>circle.
>
>-Ed
>
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