Points from strands example for Arnold instancing etc.

This isn’t an earth-shattering ground-breaking post, just a simple example of a workaround which came up on the SItoA mailing list…

In Mental Ray rendering out a copy of a Softimage ICE particle’s shape per strand point is easy, just disable the “stranddeform” attribute (when using “generate strand trails” it’s the “loft shape along strand” checkbox.) Now instead of rendering a continuous, lofted result the strand is depicted as a series of particle shapes or instances. Easy enough, and is described as a basic workflow in the softimage documentation.

But when using Arnold as a renderer, particle shapes are lofted no matter what. So how do you get a result where shapes are repeated along a strand? This is the question which came up on the mailing list, and Stefano Jannuzzo and Mathieu Leclaire posted a simple and direct solution: clone (or add manually) a point for each strandPosition on a new cloud. When using add points instead of cloning, you also need to carry over relevant information such as orientation and velocity.

This is a pretty common kind of technique for this sort of thing and is worth putting on the record where people can search for it, so I’ve implemented their suggestion in a compound and example scene here. Enjoy.