Black pixels in HDR rendering

[odimann]

When I am rendering my scene with mr and HDRi using a IBL in Maya6 I always got some black sqaures in my image. Cause they never appear at the same place, although I do the same rendering, it seems that there must be any error on my scene setup or some problems with memory buffer. The scene takes 1.2GB to render and I have only 512MB. I could not find any reason in my scene. But if any object is connected to default Lambert material i got very "white" pixels in my HDR (they have a value about 2mio?) and it seems also they are randomly placed into scene. Did anyone know about this problem and has a solution?
Thanks

[frey]

Hi,

I got the same problem, and I am not rendering HDRI, just using a Final gathering dome. Did you use imported geometry? and did you find any solution to this problem?

Morten.

[odimann]

hi frey,
sorry I did not find any solution for this problem. But I am using imported geometry with predefined normals. What I am going to do at the moment is to render to images as long as I get one without black regions or merge two images, cause the black regions are "never" the same :-/
So, this is no solution, but it works...
please let me know, if you find something about that issue.

thanx

[frey]

Hi again and thanks for the tip

Are you using imported CAD Geometry? My geometry is originally created in Catia, then exported as a wrl file. From wrl to Polytrans and then on, from polytrans to Maya. It seems as the Black spots only changes if I change the antialiasing settings. If I find a solution I will let you know.

Morten.

[odimann]

But I wish I would have a better tip...
The geometry is also from CATIA, exported to iv and imported direct into Maya. I had a similar problem with white spots, which appear when I use the default Lambert1 Material shader. But it only appears when using final gathering, unfortunetly it produces the best results...At the moment I try to render without FG but set the environment to emit light. rendering takes longer, but I did not get the black regions. but it depends on your env if it is suitable.

odimann

[joojaa]

Vour polygons probably arent connected (this is a REALY common export/import issue, and it can teake VEEEERY long time to fix for the computer so it wa<nt to be sure you absolutely NEED it before it goes ahead and does it), you cant realy se this in the viewports by default but it dfoes affect the FG algorithm. Also your normals might not realy be cossitent because of this so the fg will get e bit arbitrary values depending on where it samples (wich fg does anyway tough but not as dramatica

[frey]

I gues you mean, that the vertices is not connected? but you are probably right about that, as my geometry consist of
multiple polygons that i have merged toghether into single objects.

[frey]

Hmm,,, today I rendered the same scene on Maya for MAC OSX, it seems to help, no black pixels anymore. Both the Mac and the windows version of maya 6.0.1 uses MR v 3.3.1

[frey]

Hi, I found a workaround that works for me, I turned off the Scanline option in render panel, and the black pixels was gone, please tell me if it works for you as well

[odimann]

hi. I have also tested to turn scanline off, but it changed nothing. But I'm not rendering with final gather, I have tried to implement something like a pathtracing and it works; But it also produces some black pixels and I don't know why...but the regions are very small (about 4 pixels) so I can fix it with photoshop, *g

[frey]

Hmmm, strange after setting up a new scene the problem with the Black spots came back (((((, and this time it doesn't help to turn Scanline off.

[sawasawa]

random black pixels might be due to a final gather sample quirk or bug. Do you have any negative lights/light energy in your scene or do you have any other "dark" areas of your scene that the pixel may be oversampling form? Try a test where your pump up the final gather sample to a large number such as 20,000 and see if it still occurs.

[frey]

I actually have a point light in my scene, set to zero. Might be the problem? have to checkt it out.