On Wed, 9 Oct 2002 09:29:22 -0700, Scholl, Ed <[EMAIL PROTECTED]> wrote:
>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 No, it will not. This is because you need to actually interpolate along the edges to find out where the distance goes to zero. Your candidate edges are those at whose endpoints the distance has opposite signs. For example, if one end of your edge has a value -5 and the other end 3,then you interpolate along the edge to find out where exactly the value goes to zero. This gets you the intersection point. And if you join all of them you get the outline contour. Vaidya > > >-----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 >> >> ========================================================================== >>To unsubscribe, send email to [EMAIL PROTECTED] and include in the body >>of the message "signoff JAVA3D-INTEREST". For general help, send email to >>[EMAIL PROTECTED] and include in the body of the message "help". > > ========================================================================== >To unsubscribe, send email to [EMAIL PROTECTED] and include in the body >of the message "signoff JAVA3D-INTEREST". For general help, send email to >[EMAIL PROTECTED] and include in the body of the message "help". > > ========================================================================== >To unsubscribe, send email to [EMAIL PROTECTED] and include in the body >of the message "signoff JAVA3D-INTEREST". For general help, send email to >[EMAIL PROTECTED] and include in the body of the message "help". =========================================================================== To unsubscribe, send email to [EMAIL PROTECTED] and include in the body of the message "signoff JAVA3D-INTEREST". For general help, send email to [EMAIL PROTECTED] and include in the body of the message "help".
