Need Prim Parameterization Cheat Sheet

Hello,

I was wondering of a kind soul could point me to a parameterization cheat sheet for the prims? Specifically the torus and cone. For context, I make heavy use of RenderMan primitives in a 3D application I've built and quite enjoy them.

For example, a RenderMan torus uses an inner radius for control of hole size I'm scratching my head for how that maps to the SL torus controls. Same for cone.

Cheers,
Doug

Not sure I can really help, but I can get you a step closer.
Try a search on 'PRIM TORTURE' in the old wiki.
<I say 'old wiki' because i saw it there, and haven't had a chance to look at the new one. >
Here's a URL:
http://rpgstats.com/wiki/index.php?title=LibraryPrimTorture

"Hole Size" for SL torii/tubes/rings is a misnomer. Those numbers directly relate to the size of the cross-section being extruded, of which only the Y value directly affects the hole size (at least with no twist applied.) A Y hole size of .5 means the Y dimension of the cross section is 50% of the overall Y scale. Without any twist, the hole size will be 1 minus twice the Y Hole Size, for torii and tubes, anyway. Rings are a little different, because the width/height of triangles doesn't directly correspond to the X and Y scales.

A cone is just a tapered cylinder, which itself is just a circle extruded along a straight path.

Put simply, there are really only 7 classes of SL prims. Box, Cylinder, Prism, Tube, Torus, Ring and Sphere. And those can basically be divided into 2 subgroups, those that extrude a flat shape (square, circle or triangle) along a straight path, and those which extrude one of those three shapes along a circular path. Box/Tube extrude a square, Cylinder/Torus extrude a circle, and Prism/Ring extrude a triangle. Spheres extrude a Half- (or less) Circle around a circular path. (If you could give a Torus a Y Hole Size of 1, it would be virtually identical to a sphere, if apparently a little pointy at the poles)

Cones are tapered cylinders. Pyramids are tapered boxes (4-sided) or prisms (3-sided). The Half-sphere button creates a sphere with a 50% path cut, though personally, I think a lot of things using this shape would texture better if rotated 90 and dimpled 50% instead.

Anyhow, that may be enough to get you started on understanding how the numbers affect things. One tip: for the circular extruders, do a 50% Path Cut, and then look at how changing any of the other numbers affect the cross-section end-on. I was mystified by a lot of those options til I stumbed on that little trick, then it started making a whole lot more sense.

Very cool Deanna Trollop. Thanks for the cross section tip. Got it, prims are "extrusion-centric" beasties. I'll get on it.

Cheers,
Doug