Rendering Curves with MTOR

Rendering Maya Curves

You can render Maya curve primitives with MTOR and PRMan! Although there are several limitations, this can be quite useful for simple modeling tasks as well as with Maya soft bodies as in the modeling of hair.

The process is quite simple. First create your curves using standard Maya tools. Next, attach a special attribute to the curve which controls with cross-sectional width.

Finally, attach any RenderMan appearance to the curve and render!

MTOR Curve Rendering Attribute

The name of the special curve rendering attribute is mtorCurveWidth. Using the standard Maya attribute editor, you can attach this custom attribute to any curve primitive. Now this attribute will show up in the Maya Channels box (and other places) and you're able to control (even animate) the value from there.

Limitations of Curve Rendering

Since Maya doesn't support curve rendering directly, none of the standard rendering attributes are available on curves. This includes: castsShadows, visibleInReflections, shading engine associatations, etc.
Since the RenderMan Curves primitive doesn't support NURBS, your curve rendering may not match exactly (it's rendered as a uniform bspline). However, if you stick to simple NURBS curves with no variation of weights, you should be able to get acceptable results.
Currently we support only a constant width curves.