Thread: CSG Editing...
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Old 26th March 2004, 12:00 AM   #7
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Default Re: CSG Editing...

So, you'd be doing the overall layout with the normals facing out, so that the CSG operations can perform properly.. but when it comes to actually prep'ing it for conversion or import into a 3D game editor, you would turn them in so that the walls are facing the player.
Not usually. Unless you perform some editing operations that directly affect normals, they should transport from your finished AC3D model to most other 3D apps/games without problems.

Any/all surfaces in AC3D can be designated as 1 or 2 sided. Two sided faces can be seen from either side, but 1 sided faces can only be seen if the normal is not facing away from the camera. If you make sure all of your objects/faces are 1 sided, then if your model/level looks good in AC3D, it should look good in your export.

I doubt you'll ever have to mess with normals for game map editing.

As for the stress on normals here: AC3D offers model types that would be illegal in a pure CSG editor (standalone faces, lines, open ngons, etc), so the "outward facing normals" rule is necessary so the makers don't get questions like "why doesn't my mobius strip model Union properly with my cube". Essentially, if you stick with primitive types like boxes, pyramids, cylinders, etc (convex objects), CSG should never give you any problems.

As for the Union CSG operation.. is that what would allow a hallway to be attached to a room simply by placing the hallway mesh flush up against the room mesh and then selecting "union"? Or.. as I've seen happen in other editors, would that leave a face "closing off" the hallway from the room?
I'm assuming you mean to "cut" a hallway opening into the room? You could definitely do that using your suggested method - and yes, you would have a face blocking the hallway, but that could be easily removed or subtracted out.

The boolean plugin in AC3D has a neat feature that allows you to keep or discard either object from the original geometry from any operation. So, in this example, you may find it easier to subtract a hole for the hall without deleting the original hallway.

Also, I'm assuming that the room in your example is composed of walls with thickness. i.e., the room is composed of boxes/blocks rather than flat rectangles. If it's composed of flat (non-convex) rectangles, the CSG operations may not work properly. I'm not aware of any 3D editors that guarantee proper handling of CSG operations on non-convex objects (although I'm not familiar with Unreal's editor).

Hope that helps
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