artifacts with Transp-ray Shadows! =/

Hi,
Got this rendering here: How to avoid the artifacts in the shadow?

http://img224.imageshack.us/img224/796/output11ol.th.jpg

(86kb, sorry!)

Regards,
Chris

not sure, I know I had something similar happen, but I can’t remember how I fixed it… Are your glass objects single sided or double sided?

Oh, maybe open each object in edit mode, select all polys and remove doubles… maybe that was how I fixed the problem in my render.

they consist of cubes and got no double vertices…

Regards,
Chris

Could you post the blend so we can play with it?

Sure.

Look for it here:

http://chris.mega-backup.de/LightingTest4.blend

Regards,
Chris

I’m not really sure why that’s happening, it only seems to be a problem with the one window. I did notice you have a lot of backwards facing polys and what seemed like WAY too many polys in the window itself. I was unable to fix the problem by simply changing some settings, but maybe you could try to rebuild the windows with fewer polys and see if that helps…

Sorry I couldn’t help more…

anyone else got ANY idea? =)

Not sure why this worked, but I subdivided the glass really really highly and then added a subsurface of 1 and it fixed the problem… I’ve linked to the updated .blend

http://www.monsoonstudios.com/Blender/LightingTest4.blend

Not sure why this worked, but I subdivided the glass really really highly and then added a subsurface of 1 and it fixed the problem…

Don’t go with this solution.

Take a look at this image. It’s the corner of one of the windowframes:

It is far too complex. In fact, it’s more like erroneous than complex. This complexity in combination with the IOR of the glass makes for some strange shadows. You need to simplify the window frame.

uhm…ok, thanks! Didnt recognize this geometry fault.
Thanks.

Regards,
Chris

I tested this scene extensively… the problem still existed with only the glass present and the frames moved to a different layer. That is why I came up with the solution that I did. The frames are not at fault. It is the glass.

I tested this scene extensively… the problem still existed with only the glass present and the frames moved to a different layer. That is why I came up with the solution that I did. The frames are not at fault. It is the glass.

This it what it looks like here when I move the frames to another layer:

I also tried setting the IOR to 0 (without moving the frames to another layer), which also removes the artifacts.

BTW, I thought it was the topic starter who found the subdiv solution himself. It may appear rude what I said knowing that it was you… Sorry

That’s ok… I gave the glass a bit of transparancy fresnel and found that the glass was causing the errors on it’s own… if you render with just the window frames you won’t get the error… also if you render with only one frame of glass and the other empty… led me to believe that it was the glass causeing the problem… since you said reducing the IOR also removed the problem this really makes me think it was the glass causing the errors… I still think it is weird that subdividing the glass fixed it. Maybe it upped the calculations on the rays helping remove the error (i.e. smaller area of calculation)