I seem to run into this issue a lot.

I create a line of points, and then use the sort $TX-$TX2 .. trick to get all the normals pointing down the line (which is never a straight line down an axis . The heading and pitch are fine, but the “bank” is very often not what I want. Which is obvious when I begin to copy geo to those points and things are rolling some arbitrary amount.

I have tried using things like polyframe, and even blending normals from two sources with a vop sop without much success.

Is there some sort of “up vector” trick I don't know of. I seem to always be able to only get 2 of the 3 orientations of the normal how I want.

Thanks for any suggestions.

Hi

Check out some of my notes http://www.circusmonkey.com.au/circusmonkey/Sops.html [circusmonkey.com.au]

Rob

Thanks, lots of good info there.

I'm still not really getting what I want thought.

Basically what I want to do is have the normals flow down the mesh. I know of a trick using a vop sop and two cross-products, but again.. some work some don't.

Maybe its a stamping issue. I'm just doing a vanilla copy.. so perhaps I need to find a way to have each copy orient itself since a one size fits all transform on the mesh I am copying can only ever have some of the geo oriented properly.. ie. the chest is good, the arms are not in this example.

Any ideas?

You are aware that to have a complete description of orientation you need at least a normal and an up vector. The normal should point along the curve and the up vector defines the direction perpendicular to the curve in this case.
Looky here: http://www.sidefx.com/docs/houdini14.0/copy/instanceattrs [sidefx.com]

The easy way is to abuse a sweep sop, I attached an example. It also is not hard to implement a moving frame in a python sop, but that takes a bit more figuring out. Here is some nice information:

http://research.microsoft.com/en-us/um/people/yangliu/publication/computation%20of%20rotation%20minimizing%20frames.pdf
[research.microsoft.com]

Hope that helps,

koen

Thanks for the scene. I'll take a look and try and read up.