Hi Michael,

In post # 798.19 here you stated the following and I too think it's a great idea:

[quote]
If you export a closed solid from MoI, MoI will do some work to automatically orient normals towards the "outside" direction of the solid. But if you export open surfaces, there won't be any automatic orientation. Due to the Modo flipping bug, you won't be able to flip it properly in Modo so to render it properly you will need to turn on double-sided rendering for the render material.

I think I will tune this up so that open meshes will get a double-sided material set on them by default on export from MoI.
[/quote]

I often create MOI models for use in trueSpace as actual Virtual Environments, where via trueSpace they can be used to create fully interactive 3D Scenes, which when afterward are placed in Caligari's multi-user online servers, can be accessed via Caligari's "truePlay" program (which available to anyone free by the way) and people can walk around in these environments, meet others from all over the world, interact with the objects in these scenes, and even use directional sound and voice with other users in them.

The problem I've had in the past with making some of these environments in MOI is the issue you stated above, in that when I export these models from MOI as OBJ models and then load them into truePlace to attach interactive scripts and such, the surfaces of some of these models cannot be "walked on" as an Avatar inside the scenes or one falls right through them.

As a workaround I've used two methods all along, one being format converters which allow me to reverse normals on a per-triangle basis, and the other workaround has been using "shell" in MOI during the creation process to add a double-sided aspect to open meshes. These methods usually worked fine for me, and since my issues with this were probably unique I didn't even bother you with them.

This "double-sided material" "tune up" you mentioned in another thread here would resolve these issues for trueSpace users permanently though, and I just wanted you to know that it would be welcomed by trueSpace users as well as Modo users.

Thanks,

- 3dvisuals dude

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