OTOY Forums

Attached project renders this black square mess on the polygon surface.

It only appears at this particular camera angle
The square changes size depending on the displacement resolution
The black square changes strength depending on displacement depth
Octane 2021.1.4
C4D R25.117

Affects multiple systems, gpus, drivers

Hi,
the object is quite small, so you need to reduce the Ray Epsilon value (precision of the rays) in Kernel panel: Please note that the image used for displacement is only ~1000x1000 pixels, so it makes no sense to increase the quality to 2048.
And always better to use 32bit Linear images for Texture displacement.

Here is the modified scene: ciao,
Beppe

The 2048 displacement resolution was just there from experimenting to see what caused it and changed it.
32bit wont make any difference on such a shallow 0.1mm displacement compared to an 8 bit image.
Do you really consider a 300mm wide object to be so small that the default epsilon cannot handle it? I've never had such issues on an object this large, the default normally only fails on <1mm sized objects. also consider my scene scale is set to 1mm, not 1cm. So in terms of data sent to the render engine this is like having a 3 meter wide model as far as app decimal places go.

I can see that changing the ray epsilon fixes it, but by my understanding of the setting it makes no sense. Ray epsilon changes how small surfaces close to one another behave as they meet/intersect. Why does this effect happen in the middle of the model where no other surface comes close to the mesh?

Hi,
if you change C4D scale from centimeters to millimeters, you need to correct the Ray Epsilon accordingly.
It is the same if you change the scale to kilometers or whatever.

ciao,
Beppe