Hi 3d visuals dude, I'm not really sure how to specify double-sided materials in an OBJ format though...

OBJ materials are specified by use of a separate .mtl file, and looking through the definition of those, I didn't see anything mentioned for that.


I'm not sure if having double-sided rendering materials would really help for your "walk" through problem - I think it is possible that a collision detection system may need the actual geometry normals to be oriented as it expects, rendering materials may not apply to that situation.

Does trueSpace have a "flip normals" or "reverse" function somewhere? That's what you would want to use in this case.

I do want to add some mechanism to view and flip the normals from within MoI, but that won't be ready for the initial V1 version.

- Michael

Hi Michael,

sorry it's been so long on a reply... I had a few non-MOI issues to square away before I had a chance to get back to this forum.

I guess I misunderstood what you meant by "double-sided materials" in that other thread here then, I thought you meant that the normals would be outward-facing in relation to both sides of an open mesh's surface.

Either way, it's not really a major issue with trueSpace's Virtual Multi-User Scene designs created in MOI until you start making some very exotic an unorthodox types of structures intended for realtime user walkthroughs... I tend to do that a lot though, letting my imagination in regard to Virtual Architecture extend well beyond what real-wrold standards would allow. As a result of that tendency I get into some unusual normals issues accordingly.

No sweat though, I've found numerous related workarounds, some in MOI, some in trueSpace, and some in 3rd party utilities.

I just thought your earlier post in regard to "double-sided materials" meant you were creating some kind of new ~dual normal~ aspect to open mesh surfaces within MOI upon OBJ export, I didn't realize it applied only to rendering.

No big deal though, I'm still "a MOI Lifer"... I love this program more and more every single day!

Thanks for the clarification,

- 3dvisuals dude

Hi 3dvisuals dude,

> I thought you meant that the normals would be outward-facing in
> relation to both sides of an open mesh's surface.

One single polygon just by its nature has a "positive" and a "negative" side to it...

To make actual normals pointing on both sides would only be possible by having duplicate polygons in the mesh, with one having a reversed point ordering from the other.

Usually it isn't done that way since that increases the size of the actual mesh data, usually there is some kind of flag that you would set so that whatever is using the mesh should treat the positive and negative sides equally instead of skipping processing stuff for the negative side...

- Michael