Hi lorem,

> Why can't I use "Proj" intersection beetween main outline curve and solid at
> step2 to get separate volumes? It only creates some points on the solid...that's
> why i use the "ugly" extrusion method at stpe3....

You mean by using a Boolean command?

That won't work for your case because your shape is not a flat planar curve. For curves to interact with solids in the Boolean commands, the curve must be planar so that it has a well defined extrusion direction. Otherwise MoI is not able to figure out the extrusion direction.

If you use Edit / Trim it can work if your curve is pretty close to the surface - Trim will do a kind of "pull" on a non-planar curve towards the surface to be trimmed but it can get confused if the curve is not pretty close by the surface.

- Michael