Needed:
Model program and export plugin for xfile output.
Blender, milkshape 3D, fragmotion, wings 3d for a few of the cheaper or free ones. There is Maya and Max. they are expensive and over kill for what you need to accomplish.
Import a wall segment into the model program. Its size is
8'4" x 8'4" x 2.5". Once you have that wou can add meshes to it to make it as you like. draw wall profile and extrude them. Make a mesh and do a booleen operation to add or subtract geometry from that mesh.
Have a great texture and a lot of detail is not needed. you will need a texture anyway to do UV mapping for the mesh.
Things to make you life easier in the game when using.
Low segments or full walled segments:
Have any extrusions coming out of the wall to be not more then 5 - 10" from the wall or you will have no roon for the player to walk thru. Keep the ceiling trim ones above the players head.
Circular segments: Keep low deatail on bottom part and arch it towards the top. Watch were the corners come together and see how the collision works.
Mid or upper segements: or anywhere that their is plenty of room to get around, you can do what you like.
For custom wall segment parts other then the floor use polygon collision. Floor and ceilings use box collision.
Sketch out segment walls for straight, 45 degree walls and curved walls. to see how the edges are going to fit together when painted in the map editor.
Test, Test, Test for collision issues in tight places. (1 x 1 segment area or hall, corners)
If these are going to be small levels with maybe 36 - 50 segments in it you can do as you feel in detail. But watch the poly count in a test game to determine if you have gone over board.
That should get you going.
