Flamingo nXt

easy rendering for Rhino in Windows

Black artifacts when rendering water

Hello,

So I've been trying to render ocean water, but when I do there are black spots that show up on the surface. the spots only show up when I'm using a HDRi, but it doesn't matter what HDRi I use or what angle its set to.

 

I've created my own "ocean" material and have generated a 3D surface to represent a fully developed ocean surface. As can be seen in the attached image the dark spots seem to show up in the troughs of the waves.

 

While the black spots aren't really an issue with a still image, I am trying to render a movie and when I combine all the frames together the black spots flicker across the surface.

 

I've tried everything to make the spots go away but nothing seems to work. If any of you guys have seen this before and/or have some suggestions to solve it that would be greatly appreciated.

 

Thanks

Ian

 

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Permalink Reply by Facundo Miri on September 16, 2011 at 6:44am

Hi Ian

 

Could you post the model and the material so we can test it here?

 

Thanks


FAcundo MIri

Permalink Reply by Ian McCauley on September 16, 2011 at 7:56am

Facundo,

Here is the file.

I've switched from an HDRi to the automatic sky and the black spots are still showing up. It kind of makes me think I might have my reflection settings incorrectly set up.

As a note I have been using the latest Rhino 5 WIP (32bit) and build 32 of FlamingoNXT (32bit)

Thanks for the help.

Ian

Permalink Reply by Facundo Miri on September 16, 2011 at 9:00am

Hi Ian,

 

There was no file attached.

try changing the refraction index value.

Permalink Reply by Ian McCauley on September 16, 2011 at 9:32am

Hmm, the original file was too big.

I've killed off all but one layer and the ocean surface but still can't get the file below the 5MB limit.

Any suggestions to reduce the size more?

Thanks

Ian

Permalink Reply by Ian McCauley on September 16, 2011 at 10:05am

Aha,

Hopefully this .Zipx file will work.

 

 

 

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Permalink Reply by Facundo Miri on September 17, 2011 at 11:17am

I couldnt open the file, it gives me an error. Maybe it got corrupted.

 

I just need the water surface. use save small.

 

Facundo Miri

Permalink Reply by Ian McCauley on September 19, 2011 at 8:06am

Hmm,

Here's a dumbed down version of the surface. the mesh size is twice as large but the black spots still show up.

Thanks again for your help.

 

Ian

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Permalink Reply by Ian McCauley on September 20, 2011 at 8:25am

Facundo,

I tried messing around with the refraction index, but that didn't seem to help.

Since the black spots are happening in the troughs of waves the problem would seem to point to a reflection/refraction issue (surface is just at the right angle to not be able to reflect/refract light back to camera).

I don't know if lighting could be the problem, but I would figure that an HDRi or the automatic sky would provide enough lighting to completely light my scene.

I've run out of Ideas...

Thanks again for your help.

Ian

 

Thanks

Permalink Reply by Facundo Miri on September 20, 2011 at 8:31am
Im having a problem right now running (the last 2 days) with  Flamingo nXt, cant make it run with Rhino 5. So I cant open your file. As soon as I solve this, I will test your file first. Hope I can find any ideas about what is causing this problem.
Permalink Reply by Facundo Miri on September 20, 2011 at 10:58am

I've done some tests, the balck spots are created by the sky. I have changed the sky listh to channel 5 to test it.

See attached images, with sky intensity set to 0 there are no black spots. but the scene looks totally different.

I think i would try is to create a big box below the ocean water so you dont get any light from the bottom (trying to duplicate a real ocean water) maybe that can eliminate the black spots.

Permalink Reply by Scott Davidson on September 20, 2011 at 11:30am
Another way to address this is with transparency.  I believe that in some cases the rays are dropping through the water into the blackness under the water.  I turned the transparency to 0. To compensate for this, I ran up the highlight intensity, fresnel.  Then I made the diffuse color darker.  This is the result.
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Permalink Reply by Ian McCauley on September 20, 2011 at 12:43pm

Thanks for the input,

Enclosing a volume below the surface unfortunately does not affect the black spots.

The 0.0 transparency method does seem to give good results, however I won't know for sure until I render a short video to see if there is still noticable flickering.

I'll set up a run tonight to see how it works.

 

Thanks

Ian

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