Just to add a little more to Paul Pantera's e-mail.... The Triangulator in Java3D is a Polygon Triangulator - a specific case of general purpose Triangulators based on Delaunay, advancing front etc. If you feed in an n-sided polygon to the Triangulator, it will generate n-2 triangles AND will do so WITHOUT generating any new verticies in the interior or on the boundary. Thus, the grid density is automatically predefined by the input polygon.
Even a simple quad is in general not guaranteed to be planar. If a non -planar quad is fed to the Triangulator it will ( as above ) produce just 2 triangles and these may not be hugging the quad surface at all. To get a high-fidelity triangulation of such a quad, you could subdivide the quad into a few more quads and feed them all together as a quad array to the Triangulator. Raj Vaidya On Wed, 17 Oct 2001 12:19:42 -0700, Paul Pantera <[EMAIL PROTECTED]> wrote: >The triangulator is designed to work on planar polygons. If >your polygon isn't planar, it's projected onto a plane. It's >not designed to work on a half cylindrical surface made up of >a single curved polygon. It simply turns polygons into >triangles. > >-Paul > > >> Delivered-To: [EMAIL PROTECTED] >> MIME-Version: 1.0 >> Date: Wed, 17 Oct 2001 11:30:08 -0700 >> From: Rajamiyer Ravichandran <[EMAIL PROTECTED]> >> Subject: Re: [JAVA3D] Possible to control trianglulator? >> To: [EMAIL PROTECTED] >> >> My experience with Triangulator has been disappointing >> particularly for the curved surfaces. For example, I >> have a half cylindrical surface with a hole in it. >> Since there is no way to control the triangle density, >> I see a triangle fan. Also many triangles are not >> exactly on the cylindrical surface. Some of the edges >> of the triangles form a chord along the cylindrical >> edge. There could be a serious falw in the >> triangulator algorithm. >> >> Now from the GeometryInfo object I create a "Delaunay >> Triangulation" myself instead of relying on the >> Triangulator class. I wish they provide the sourec >> code of the class. >> >> Ravi >> >> >> >> --- "Dvorak, Daniel J." >> <[EMAIL PROTECTED]> wrote: >> > In looking at the coordinates contained in a >> > GeometryArray, I just >> > discovered that the Triangulator is dividing a >> > simple 4-sided polygon into >> > what looks like a triangle fan with 14 triangles. I >> > believe this is causing >> > my application to take much more memory than it >> > should, as I'm drawing a lot >> > of 4-sided polygons. >> > >> > I use GeometryInfo to load my geometry. Is there >> > some way to specify the >> > triangle density that the triangulator generates? >> > In my application, two >> > triangles would be sufficient for a 4-sided polygon, >> > and would probably >> > conserve memory. >> > >> > Daniel Dvorak >> > >> >> >> __________________________________________________ >> Do You Yahoo!? >> Make a great connection at Yahoo! Personals. >> http://personals.yahoo.com >> >> =========================================================================== >> 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".
