By: DaveA
[email protected]

As you may or may not know, polygons have two distinct sides. You can prove this to yourself by flying around in the 3d view in the editor, and watch as you move from one side of a polygon to another. The side you can see is the good one.

There may be times when you need to turn one around. If you are doing Zone Portals, this is likely to happen to you. Zone Portals are generally 'sheets' which are just simple polygons (not part of a polyhedron, or 3d brush, as such). These are easy to turn by hand.

Pick a view where the sheet is edge-on to you (looks like a line). Vertex edit: let's say you have a rectangle, vertices A,B,C,D, and A & B are overlapped, as are C & D.

Drag vertex A out, which gives you a triangle.

Drag the one that was under A, namely B, out of the way too.

Now, drag the other end's vertices (C and D) to the spot where the first ones were, A & B's original position.

C and D overlapping again.

Then, drag A & B to where C & D were originally.

You now have the polygon reversed. Vertex editing ruins any surface alignment, so select the surface and hit F5 to fix it.

If anyone knows an easier way to do this, let me know.

If you want to turn a polygon around which is part of a brush, export the brush or level to t3d format. Find the polygon. You can try flipping the signs on all the components of the Normal. You could also try reversing the order the vertices are defined. I'm not really sure it that would override the normals.