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starbase1
10-02-2009, 03:07 AM
I am getting an odd effect where some areas render black.

The object is a simple hoop, 100m radius, with the lowest part touching the origin. (For those who know it, I am doing Niven's Ringworld).

The attached image, problem.jpg, shows the issue.

A couple of other odd things:


The polygons go right across the hoop, so it is only affecting part of a polygon.
I tried different camera types, with the same result.
I tried different light types with the same result.
If I crank up luminous on the surface, it starts to appear in the dark areas (which suggests a shading issue?)


The only odd thing I can see that might be a more definite clue is that when I look in modeller, the positions of the normal indicators are not consistent. (See wire.png).

All polys are quads, there are no non planar polys.

Anyone got any ideas?
Nick

biliousfrog
10-02-2009, 05:02 AM
no attached images ;)

Otterman
10-02-2009, 05:04 AM
No image attached Nick. I may be way off here butf rom my experience-black polys are a result of twisted geometry. Triple sometimes fixes it!

Nangleator
10-02-2009, 06:29 AM
Jeez, Ringworld. I modeled it to scale once. The numbers are insane.

Texturing was another thing altogether. It screams out for a good procedural terrain texture, which is as much science fiction as the ring itself.

starbase1
10-02-2009, 06:47 AM
Whoops! Images now attached.

starbase1
10-02-2009, 06:51 AM
No image attached Nick. I may be way off here butf rom my experience-black polys are a result of twisted geometry. Triple sometimes fixes it!

I tired triple, and also checked for non planar.
I did find some doubled uppolys while re-examining, but that did not fix the problem?!?!

Nick

starbase1
10-02-2009, 07:12 AM
Jeez, Ringworld. I modeled it to scale once. The numbers are insane.

Texturing was another thing altogether. It screams out for a good procedural terrain texture, which is as much science fiction as the ring itself.

You are correct!

The scale is why I kept part close to the origin, I figure that numerical errors will be reduced if I do that.

I am considering using a procedural mask to mix between various image maps - which should hide the repetition well.

I already have textures on the base, and also shadow squares - I know this does not match the book, but featureless looks awful.

Nick

starbase1
10-02-2009, 11:11 AM
OK, thanks to those who chipped in, I found it, though it was a new one on me...

It did not like the way the inner surface was in the same positionas the outer, even though both were single sided. I had not seen this before.

I scaled the inner surface by 99.999% and it fixed things.

In case anyone is interested, here are a couple of stills, and a QTVR. I'm still working on this, but I think I am getting there.

Nick