Random Black Triangles on Animation Export

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Random Black Triangles on Animation Export

Postby Collin Alexander » Sat Dec 22, 2007 4:09 pm

I've been exporting animations for my movie. JPEG codec seems by far the best quality. Unfortunately some frames get these random black triangles on faces. In another thread Ross McIntosh said it had to do with shadows, but I'm getting the problem with shadows off or on.

I'm using Mac OSX 10.4.11 on a G4 laptop.
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Collin Alexander 
 

Re: Random Black Triangles on Animation Export

Postby Collin Alexander » Sat Dec 22, 2007 6:08 pm

With shadows off, the random triangles are still there, but they are blue and gray instead of black. This is still with JPEG animation.
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Collin Alexander 
 

Re: Random Black Triangles on Animation Export

Postby Ross Macintosh » Sat Dec 22, 2007 6:31 pm

Collin -- can you try making a very brief animation (small file size) that you can upload as an example of the problem you are seeing. It might help clarify your problem. Maybe someone will know how to help.

Regards, Ross
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Ross Macintosh 
 

Re: Random Black Triangles on Animation Export

Postby Collin Alexander » Sat Dec 22, 2007 11:33 pm

Here is an example of the problem. I originally exported this as JPEG animation, 29.97 frames /second. This is a gif of just 8 frames, 1/second.

This one was with shadows off. Notice the random triangles that appear and disappear.






-CA
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Collin Alexander 
 

Re: Random Black Triangles on Animation Export

Postby Gaieus » Sun Dec 23, 2007 8:42 am

Hi, Thanks. Looks really interesting - I have a (actually two) suspicion(s):
  • Could it be "Z-fighting"? Can you make sure there are no two faces "competing" for visibility?
  • or could it be the classical clipping phenomenon? It looks that you are in either parallel projection or two point perspective - if so, could you try to switch to perspective camera mode and try the animation again?
Ultimately, would you mind sharing the skp file as well? I have never had this problem with animations...
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Gaieus 
 

Re: Random Black Triangles on Animation Export

Postby Collin Alexander » Sun Dec 23, 2007 10:56 pm

Here is a SU model you can use to generate the problem.

http://sketchup.google.com/3dwarehouse/ ... revstart=0
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Collin Alexander 
 

Re: Random Black Triangles on Animation Export

Postby Collin Alexander » Sun Dec 23, 2007 10:57 pm

I don't think it's Z fighting, but who knows.

I was using perspective, not parallel or 2-point projections.
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Collin Alexander 
 

Re: Random Black Triangles on Animation Export

Postby Gaieus » Mon Dec 24, 2007 10:10 am

Hi Collin,

Sure I couldn't see any Z-fighting. Still it may be clipping (although I'm not sure it appears during an animation export, too) for the "physical" size of the model is rather big (I mean thousands of feet).

also I noticed that there are about a dozen of GE Terrains in your model. I don't know if this may have such an effect but I'm sure you'll have some problems if you intend to place the model in GE.

Yet another thing; you have quite a lot of back faces in your model (see the blue faces in monochrome mode). Previously GE could not handle back faces but now (afaik) when there is a photo image on them, it shows them correctly (though still having some problems with other textures/colours).
I'm almost certain about this not causing those triangles though they seem to be blue when appearing. You could give a shot though and fix this problem by reversing the faces and applying the images on the front faces again to check if it fixes it.

Still an interesting phenomenon even if you are certainly not pleased with it...
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Gaieus 
 

Re: Random Black Triangles on Animation Export

Postby Anssi » Mon Dec 24, 2007 10:45 pm

Hi Collin,

I certainly saw some z-fighting in your model, in the areas where the different imported aerial images overlapped each other. On such a large model, I wouldn't be surprised about clipping effects either, but I didn't see any of that, but what is shown on your short animation looks very much like that. Then there are the third type of aberrations, called shadow clipping, which show up when you turn on shadows, and fly through them. That is a known SU bug-search the forum for Carmac's reverse for more information.

Anssi
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Anssi 
 

Re: Random Black Triangles on Animation Export

Postby Gaieus » Mon Dec 24, 2007 11:09 pm

Yes, right, I also saw the Z fight on the terrain but did not count that for I guess he's just using them as placeholders...
:roll:
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Gaieus 
 

Re: Random Black Triangles on Animation Export

Postby Collin Alexander » Wed Dec 26, 2007 12:33 am

Thanks for the input. By the way, how can I get rid of the Google Earth terrain? I can turn off the visibility of it, but I'm unable to select and delete it.

The building models were done individually, and georeferenced. The whole model was put together from those individual models. I'm actually using a version with even more stuff in it than the one I linked.

Anyway, any input on how to solve the clipping effects?

Might the random triangles somehow be related to the z fighting (wouldn't it be y fighting ??) in the google earth terrain.
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Collin Alexander 
 

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