surface substraction

[Anonymous]

hello everyone.
I've done a surface with archiforma coons surface tool. And now I need to substract with upwards extrusion some elements below this surface. But the problem is that my sutface doesn't work as an operator within boolean operation palette. I can use it only as a target.
I tried to make my surface "solid" by its extrusion in Zoom Gdl, but even extruded this surface is empty inside and I can't do anything with it.

Can somebody help me, plzzz

[Aussie John]

I suspect it is like the mesh when used just as a surface, that is, it doesnt act as an operator. As there is no mass it cant do the operation.
Some prisms are similar if the masking is set to just show only some surfaces

[Anonymous]

I've figured out the name of my problem! It is AC 9!
And the answer is AC 8.1!

I tried to do the same in previous version (8.1) and my surface began "to work" as an operator. But the name of the operation I needed is not the substraction with upwards extrusion! It is intersection!!?
In my case intersection works the same way as it works with a mesh when you try to cut something with a mesh. But you can use this command even for surface meshes in AC 81!!! and only for solid ones in AC 9

So, the decision of my problem lies on the surface (heh...) in previous version of ArchiCAD!!!
Is it the right way you going, Graphisoft?