Problems with normals and tori

[eburacum45]

I think someone else had this problem too;

Ihave made a simple model of a Stanford Torus (a rotating habitat design), using Anim8tor; but when I import it into Celestia, the inward facing face of the torus disappears.
Here is an image
http://tinypic.com/1p86jq

Is this just my system, or is there a way of fixing it? Anim8tor has functions called fix normals/flip normals, but they don't seem to acheive very much.
Is the CMOD format any help? (to be honest I have the converter program but I don't know how to use it.)

[selden]

Current versions of Celestia (v1.3.2 & 1.4.0pre#) have a bug related to how partially transparent surfaces are handled. Is the surface texture a PNG or DDS image that includes "windows" perhaps?

Alternatively, can you make a copy of your model available so it can be tested on other systems?

[eburacum45]

Yes, that is probably part of the problem; the window faces inwards on the Stanford torus, toward a conical mirror; this window is drawn as if the whole torus were transparent at that point, instead of revealing the floor of the torus behind.
The conical mirror is also shown; it is itself only half displayed (by rights it should be bathed in bright sunlight from the mirror surface- but that is not possible).

Hmmm; what would be really nice would be if these models couls display emmissive areas...

[chris]

The problem here is not Celestia's limitation with rendering partially transparent geometry. Rather it's that your torus doesn't have any backfaces. Most meshes are generated with one-sided triangles, i.e. the triangles are visible only from the outside of the model. This isn't ordinarly a problem, but in the case of your torus, the transparent window allows the outer shell of the your model to be viewed from the inside as well as the outside. You need to duplicate the outer shell geometry and reverse the orientation of the triangles in it so that it's visible from the inside. I'm afraid that I don't know how to do this in Anim8tor.

--Chris

[eburacum45]

Thank you;
I wondered if that might solve the problem. I'll try something along those lines.
I'll have to make a simplified version as well for our Freehauler spacetrader simulator; that can't handle these big, smooth, doublefaced models.

[Beowulf01]

Ohh hell, this is the problem i hve been expreiancing with my model of a L-5 habitat.
so far its been VERY slow going.

add to tht i seem to be reaching the limit of the amout of polys that teh 3DS file type can handel...
drat.
Ill try tihis, Thanks to both eburacum45 and Chris.

[TERRIER]

.....You need to duplicate the outer shell geometry and reverse the orientation of the triangles in it so that it's visible from the inside. I'm afraid that I don't know how to do this in Anim8tor.

--Chris

Have you tried the "shell" mode ? It allows you to add thickness to the walls of an object. Thus resulting in both sides of the wall having surface normals facing the correct way.

The latest version of anim8or v0.9 (dated 29-1-05) includes this feature.

To have the correct surface normals on both faces of the Stanford Torus model, you can quite easily do it as follows;

Build an open ended cylinder to the required dimensions.
Change it to a mesh.
Go into Point Edit mode and select the Shell icon from the side toolbar. (The shell mode icon looks like one 'U' inside another)
Select a point and drag your mouse to give the wall the desired thickness.

Et Viola !

Hope this helps ?

TERRIER

[eburacum45]

Thank you, TERRIER; I'll try that next time.
This time I have fixed it by making a three dimensional floor of parkland inside the torus; this also gives the inhabitants somehere to stand.
I've added radiators , a nuclear generator and solar panels as per the original design as well.

http://tinypic.com/1pjn0g