Ray Epsilon Tweet

[pryzm]

Seems I'm at an impasse with Ray epsilon. No matte what I do, I can't make the self shadowing diminish. It just moves across the model. I've tried even smaller, and even larger to no avail. Any thoughts?
.25 0.125 .1mil (respectively) The shadowing is on the left in the first image, moves right in the second image, is on the right in the third image. It's also on the center popup in the first image.

This shadowing just moves around whichever setting.

[juanjgon]

But what's the scale of this scene? I'm not sure if this is a ray epsilon issue. If you are working in meters (1 unit = 1 meter), usually the default small epsilon value works fine. Are you sure that you don't have overlapped polygons?

Thanks,
-Juanjo

[pryzm]

Thanks Juanjo, yeah the scale is in feet (1 unit = 1 foot) and I don't have any overlapped polys. This doesn't happen with smaller houses/buildings I've done (and nothing changes because I always start from the same scene file), but it seems to rear it's ugly head for these larger projects (where the buildings are 80'x100'). I move the camera and the "shadows" move as well (when distance/rotation from camera changes).

My understanding of ray epsilon comes from this post:

viewtopic.php?f=9&t=48425#p241445

so I don't know if I'm on the right track...the shadows change when I adjust the epsilon numbers. Too high/low and I start seeing shadows of the triangularized polys.

thanks!

[juanjgon]

And what happens if you set a small value, for example, 0.0001 or 0.00001?

Thanks,
-Juanjo

[pryzm]

0.0001 is .1 mil (so I've tried that) and 0.00001 gives the same result as 0.0001. I re-rendered those two settings (top image is 0.0001 and bottom is 0.00001 with red circles) and added the images below. Doesn't seem to change much as I go any lower than 0.0001

thanks for helping me get to the bottom of this.

[juanjgon]

Can you please send me the scene with the main object? I wonder if it could be far of the world origin or something like that.

Thanks,
-Juanjo

[pryzm]

Yeah, I will. The origin is right in the middle of the building

Thanks for looking at it.

[juanjgon]

I think that the problem comes from the displacement. You are using a highly contrasted displacement texture with very small details that probably is reaching the precision limits of the Octane kernels. I'm not sure how to resolve something like that, but probably you need a less detailed displacement map, or even better, to get the kind of subtle detail that you are looking for the walls, the bump mapping (or even a normal map) can be enough and a lot faster to render.

Hope it helps,
-Juanjo

[pryzm]

Thanks Juanjo. I could never get what I wanted from a bump map (looked fake), so I reverted to displacement. I think you're right though, if I move the camera toward the building or change the image to a less contrasting version the problem goes away. It doesn't happen on the other smaller buildings I do because the camera isn't as far away to have such small detail.

You've done it once again, thanks for the help!