No worries - I've had that, and it drove me nuts. Someone else had it at work, it drove them nuts and took me ages to suggest that it could be the problem.
I must remember to get it put into our tech documentation.
The fix would be this: Apparently max can tell facing direction based on the W factor of the UVW modifier. It's how a game engine knows to alter the normals of the mirrored faces to display properly. If when baking, max would ignore all faces with a negative W value, we would be A ok. As it is, I use unwrap tools to move all the mirrored chunks over 1 unit in the U direction, and then use it to move it back after rendering.
I always thought W was a positional unit, rather than a directional one. In my mind's eye I imagine UVW to be like XYZ, three axes to place UVW coords into.
I can really see it when messing with a 3d texture like a procedural, where moving through W is basically moving on a vector perpendicular to UV.
So as I understand it, merely moving a XYplane into -Z territory wouldn't be the same as mirroring the plane across X or Y, since in the former case the "normal" is still facing out, while in the latter the normal is facing in.
The way I hear it, coders find out the normals (mirrored or not) of the UV triangles by examining the face-winding... the order the vertices were created. Like when you manually create a triangle by clicking verts in a certain order.
Well I guess this is kind of esoteric, but I'm interested in learning about it anyway.
Hey poop...
Y'know, esoteric is good. Try explaining transform distortion caused by stack modifying vertices below the transform to first years. They go all gooey and if you poke them they fall over.
You can cut away the mirrored faces using an edit poly modifier to temporarily clean them away while you do your render to texture.
The problem with that dave, is that it kills your normals. You want the normals to stay the same on the edge as they will be in the game. REally it's best/easiest (those are hardly every the same thing, but in this case it is) to just select all the mirrored faces, and using unwrap tools, move them over 1.0 in the U direction. This will keep max from trying to overlap during the bake, but the engine and max will still apply your final texture to the correct faces. It's a great way to take care of the mirroring.
So with the discard strips is the idea to first add an Edit Poly mod and delete away the mirrored polys, second extrude the open edges a bit, third cast your rays, then fourth delete the mod?
Replies
I must remember to get it put into our tech documentation.
I can really see it when messing with a 3d texture like a procedural, where moving through W is basically moving on a vector perpendicular to UV.
So as I understand it, merely moving a XYplane into -Z territory wouldn't be the same as mirroring the plane across X or Y, since in the former case the "normal" is still facing out, while in the latter the normal is facing in.
The way I hear it, coders find out the normals (mirrored or not) of the UV triangles by examining the face-winding... the order the vertices were created. Like when you manually create a triangle by clicking verts in a certain order.
Well I guess this is kind of esoteric, but I'm interested in learning about it anyway.
Y'know, esoteric is good. Try explaining transform distortion caused by stack modifying vertices below the transform to first years. They go all gooey and if you poke them they fall over.
You can cut away the mirrored faces using an edit poly modifier to temporarily clean them away while you do your render to texture.
Your way is cool also.