No smooth surfaces Tweet

[davorin]

Good morning

This is odd...or I just don't know how to do it...

If I just place a simple sphere and assign no material the surface looks kinda smooth though the shadow doesn't follow the sphere but the mesh preview.
It also makes no difference when choosing smooth or flat in the tools menu:

Sphere with no material set

As soon I assign a material the smoothness is gone and I have to set it in the material node...though the shadow is still rough and doesn't follow the sphere...

Sphere with material assigned

Is Octane unable to render perfect spheres or round edges?

[dktw]

hi,
try checking "smooth" box in shader node

[davorin]

Yes...and the result is above..the orange sphere...

Pretty ugly for "smooth" (o;

Especially the shadow...

[milanm]

This is known as the "terminator problem". It's well known in cg industry. TL;DR: -> You need more polygons to better define your geometry for a raytracing/pathtracing algorithm unless you are planing to fake your shadows in compositing or adjust rayepsilon. It's normal. There was a huge discussion about this a long time ago on these forums but I am simply too tired to look for it now.

This exists in all render engines that are calculating shadows by tracing rays.

It's more pronounced for directional and really small lights. You can reduce it by increasing the 'sun size' or the size of your mesh lights (to make a 'softer' shadow) or,again ,by adding more polygons to your geometry.

Here is a reference if you want to learn why is that happening:
https://fenix.tecnico.ulisboa.pt/downloadFile/1689468335601264/Its-Really-Not-a-Rendering-Bug-You-see....pdf

Cheers
Milan

[grimm]

Adding bump or normal textures help as well.

[milanm]

grimm, you've inspired me to try another method.

I always thought this should work in theory but I never had a good reason to test it. Just tried it and it worked great -> Try adding a 0.01 amount displacement. It's enough to basically teselate the object into voxels and eliminate this problem. Any texture map will do.

Cheers
Milan

[grimm]

Ha, cool, great idea!

[J.C]

grimm, you've inspired me to try another method.

I always thought this should work in theory but I never had a good reason to test it. Just tried it and it worked great -> Try adding a 0.01 amount displacement. It's enough to basically teselate the object into voxels and eliminate this problem. Any texture map will do.

lowpolysphere.JPG

Cheers
Milan

That's awesome idea

[davorin]

Hmm..I don't see any difference adding a texture to displacement...

Beides...there is no option to enter a numeric value for displacement in Blender.

[grimm]

I took a couple of quick screenshots to show how this is done. The fist capture shows the terminal issue with displacement unconnected:

And here it is with displacement connected and I drew an arrow to the height setting, which I just left as default:

You do have to make sure you UV unwrap the sphere for it to work.

Jason