CompuServe Messages

<< I _said_ about spline patches in GENERAL! Am I supposed to believe you're not beta-ing r4 (at least the patches), though?<g> >> No, I'm not testing anything for R4 – honestly. If I was, you asked, and I couldn't comment – I'd just say "I can't comment". But in this case, I can honestly say I don't know as much as most of you here – 'cause I didn't go to SIGGRAPH, and I'm really not testing any R4 stuff. If there's something specific anyone would like to know about Patch Modeling, I'll try to answer it. But in general: The Bezier patch is just a net or matrix using Bezier curves as boundary curves to define the patch. The advantages of using them in model construction can best be described with an illustration. Take a 3X3 polygon grid…if you wanted to model this into a flying carpet-looking thing, first you'd need a much higher resolution grid mesh to begin with – and thus a lot more vertices to deal with. Then, to approximate the gracefully sweeping contours, you'd have to perform tedious multiple vertex selections, and apply rotations to form the graceful contours…..a pain. If you displaced a single vertex in a 3×3 polygon mesh, you'd get a sharp spike, and likely get shading problems. With the patch, displace a CV and you get a graceful contour, which would take a much higher-res polymesh and a lot of work, as I said. You could model your flying carpet with a few selections/displacements. Also, the patch modeler has to deal with maintaining tangency & continuity at the intersection of patches "sewn together" – initially & dynamically, as the composite is deformed. Again, this would be very difficult & tedious if attempted with several polymeshes manually. Finally, you (or the program) has the ability to variably subdivide the mesh at render time, and this can be used to perform the adaptive tessellation based on proximity to the camera, as implied in the PR. Also, interpolation of the normals generally should provided a smoother shading than working with polymeshes, or the curved surface could even be rendered as a surface, rather than a bunch of triangles. So with a decent system, you can see the curves as you model and can control the UV density for visulaization purposes, are only working with a minimum number of CV's at a time which produce similar results to many polygon vertices & manipulations, and since you're working with curves, there should be more powerful deformation tools to help quickly "mold" the patches as desired. The system takes care of the normals, patch subdivision, and maintaining surface continuity – or you can override the system. Finally, texture mapping can be automatic, causing the map to conform to the contours of the patch mesh. I personally like working freeform with NURBS curves/surfaces, but a good patch modeler can be a very powerful addition in the right hands, and should be a most welcome addition to 3DS. BILL