Hello

I have intersting problem.

I need to create comething like moving tree year rings.

So my setup should be

1, maya animation of some guy, then render sequence of frames with only surface shader or use only alpha
2, in houdini use trace sop, offset curve from trace and skin it so I have little peace of surface which will moving with sequence of pictures.
3, mapping year ring texture. then offset again curves resample it, less details and repeat this step many time, so I have offseting moving year rings.

Problems:
first problem is with offseting curve,curve could be very zigzag. I cant find any tool for that. I found peak, but there is problem with normals. How could I fix it?
another problem is with mapping. I leave skin surface uncheck convert ot poly, so surface is nurbs? so I could map textures by S and T right? But number of points will be different every frame, texture will shake? another thing, will I have acces to tile texture if i use S and T?

Any ideas how to easy and quick solve this interesting example? Sorry for that stupid questions but still much much thing to learn in houdini. Thanks a lot BC

I use the Extrude SOP to offset curves. Yes I know. Yet another instance where the name of the sop has nothing to do what it can do. Part of mastering Houdini.

As for the uv's, yes if you have a NURBs surface skinned from NURBs curves then you can use the UV Texture SOP set to either Uniform, Arc Length or Average and see which one is the most stable. As for where the uv starts, well that's trial and error to see if it swims on you out of the Trace SOP.

The Trace SOP itself can generate uv's that allow you to map back on the image that generated the curves. I don't know if that set of uv's is of any use but useful to know they exist.

See the attached example file.

perfect, it works, thanks a lot…BC…