Hi there, I got a huge problem here. The thing is, I got a structure (that can be everything, from a simple cube to a technical device). For simplicty, we just assume a cube. The cube is divided into 6 surfaces which, in turn, are made of a set of faces (triangles). Now I am laying a clipplane through this cube (arbitrarily). If I take now all the points where the clipplane and the structure intersect and make a new polygon out of them, I got a new surface. That´s what the task is. So far so good. BUT the problem is, the points that I got from the intersection test don´t have a particular order. Thus I can only construct 2D-cutplanes from convex objects. If they are not convex (or if the got a hole inside) the newly constructed polygon is wrong. So for a.m. cube, this works quite nice. But for a torus this wouldn´t work. Or for a sphere, that has a hole inside shaped like a little sphere. If I´d lay a clipplane right through the middle of this object and visualized the therewith created plane, I would get a plane in the shape of a disc (without hole) :(. My question is, am I at a dead end? How can I make it work for concave objects as well, if I don´t have any additional information (only a set of intersection points)? What information would I need ? If anybody has experience with this, I would be so glad if you could help. Thanks a lot. SirTwist

Do you actually need the surface or do you just need to render it? If you only need to render it then you can you adapt the technique given in the red book. Look at this old post for an example.

Enigma

EDIT: Thanks _DarkWIng_.

[Edited by - Enigma on September 10, 2004 4:13:26 PM]

Enigma : You missed a f (href). Clicky.

Have a look at some CSG papers. It's not an easy topic, but for 2D it shouldn't be too hard. Specialy if it doesn't need to be realtime.