Thread View: comp.sys.next.programmer
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Started by Shane G. Artis
Sun, 11 Oct 1992 22:12
Using NeXT 3D kit to dump tesselated surfaces
Author: Shane G. Artis
Date: Sun, 11 Oct 1992 22:12
Date: Sun, 11 Oct 1992 22:12
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Hi, I've found by using the 3D kit on RIB files that I can produce good wireframe views of the 3D images by choosing a wireframe model. My goal is to dump RIB primitives and composite solids into polygonal patches which I can render with a ray-tracer (instead of prman which doesn't support ray-tracing). Is there any way to get at the (x,y,z) coordinate data of the wireframe solids being drawn on the screen by methods such as renderSelf:, or using the RenderMan interface commands directly? This would make the 3DKit a high-quality surface tesselator for solids, patches, NURBS, and so on which is a useful ability. Any clues would be appreciated. My instinct is to use the convertPoints:fromSpace methods and their ilk found in the N3DShape and N3DCamera objects, but I don't see an immediate or even sneaky low-level way to get at the points. Help much appreciated! Regards, Shane
Re: Using NeXT 3D kit to dump tesselated surfaces
Author: Nate Sammons
Date: Mon, 12 Oct 1992 04:03
Date: Mon, 12 Oct 1992 04:03
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Well, If you are looking for a sneaky way to do this on a low level, the lowest I can think of is manipulating the RIB file directly, and bypassing the 3DKit. As I assume you know, RIB files are just text... so it is a simple matter to get at them... I don't want to make it sound too simple, but writing a program to parse a text file and convert the wanted parts should not be that hard. 'hope this helps. -nate ns111310@longs.lance.colostate.edu
Re: Using NeXT 3D kit to dump tesselated surfaces
Author: Shane G. Artis
Date: Mon, 12 Oct 1992 16:11
Date: Mon, 12 Oct 1992 16:11
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In article <Oct12.040326.76442@yuma.ACNS.ColoState.EDU> ns111310@longs.LANCE.ColoState.Edu (Nate Sammons) writes: >Well, > >If you are looking for a sneaky way to do this on a low level, >the lowest I can think of is manipulating the RIB file directly, >and bypassing the 3DKit. As I assume you know, RIB files are just >text... so it is a simple matter to get at them... I don't want to >make it sound too simple, but writing a program to parse a text >file and convert the wanted parts should not be that hard. > >'hope this helps. > >-nate > ns111310@longs.lance.colostate.edu Actually this is exactly what I'm trying to avoid. Tesselating surfaces given the surface paramtrization only is a huge and difficult job, especially when you're dealing with NURB patches, Constructive Solid Geometry objects, and so on. Try writing a program that dumps the subtraction of a cylinger from a sphere as a surface of polygons and you'll see what I mean. However, the 3Dkit does this all automatically so I want to get at its results. In addition, the 3Dkit knows how to maintain object hierarchies, keep track of surfaces associated with those objects, and so on. I _don't_ want to reinvent this wheel! Anyway, thanks for trying to help. Anyone have any other ideas? Shane
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