Jon Parker

The way I see opacity, is that it is a rendering shortcut for materials that are assumed to have holes in them that are too small too see. The amount of opacity is inverse to the porousness of the surface / volume.

tapoh
thanks! and how this can be achieved along all three axes x,y,z?

Without testing, probably like:

I assume you need the individual curves to be known… otherwise you can grab an entire attribute efficiently using functions like this one:

http://www.sidefx.com/docs/houdini/hom/hou/Geometry.html#pointFloatAttribValuesAsString [www.sidefx.com]