Part of an obj won't render?

[trailgirl]

I'm not sure if this is a Terragen question or a Cheetah3D issue, I have searched both forums but haven't figured this one out. I created an object in Cheetah3d (Explorer 1 satellite) and exported as .obj + .mtl and placed it in Terragen in orbit above the planet (I love the copy/paste coordinates btw!). When I render, there is a part that does not render at all. It does render in Cheetah3d. The part (a cone) has the same material as another part that renders fine (a cylinder). I thought maybe there's an issue with two parts sharing the same material so I created a material just for the cone and tried that. It still doesn't appear. I also tried selecting "Flip Normals" and also deselected "Double sided surface". I went back to Cheetah3d and deleted the polygons that don't actually appear (the bottom of the cone), but no luck.

[neuspadrin]

Can you try running it through poseray? A lot of obj issues often can get fixed by putting it through pose ray and then exporting it from there.

[Mandrake]

Check the normals.

[rcallicotte]

Mandrake is probably right.  PoseRay is helpful, like neuspardin mentioned.  If it looks good in PoseRay, it should be good for TG2. 

It's also possible you need to check your textures are in the right place for TG2, per object breakdown in your model.

[trailgirl]

Thanks, it's working now. I didn't try Poseray but that gave me the idea to try Blender since I already had it installed. I imported the .obj file and then exported right back out. This time it worked in Terragen except the colors were in the wrong places, so I re-exported the .mtl file from Cheetah3d and now everything's rendering correctly. Not sure what the problem is with the Cheetah export, it usually works. I looked at the Cheetah .obj file with Textedit when Mandrake mentioned the normals and it seems to have exported the normals for the nose cone but maybe something was wrong with them.

[gregsandor]

The first thing I check when parts of a model do not render is whether there are any 5-sided polygons.  (always causes a problem)
http://forums.planetside.co.uk/index.php?topic=4449.0

Also TG has a clipping problem when the camera intersects the bounding box of a model.  (doesn't always cause a problem)
http://forums.planetside.co.uk/index.php?topic=5012.msg67011#msg67011

[Mandrake]

Trail girl

Are you a new modeler?

Greg is right when he says that n-gons are a bad thing. But they are not always a bad thing.
In the logo below, I have tons of ngons in the black areas.
I could spend time to correct the geometry in these areas but it is totally unnecessary, they render fine.
If on the other hand I creep up to the lower right hand corner and try to look down the edge...
It will not render in TG2 IF TG2 aspects are applied. Chrome settings will make the black disappear. The orange will remain.
Regular black.. no problem, renders correctly no matter how close I get.

The reason I suggested Poseray is the you can inspect your model very closely, in preview mode, if you see holes in your model, they WILL be there in TG2.
I'm not familiar with you modeling programs, so I can't go any further..

If you download models and try to import them to TG2 by running them through PoseRay, you run risks of failure! NO Two ways about it.
This model that I've made in C4d, Took quiet a bit of Scrutiney!
http://www.terragen.org/gallery/displayimage.php?pos=-5908
And it's still a wip.. There are a number of ngons on the crew compartment, just checked 11 ngons, I could do away with them but it's moot..