Surface Normals Flipped

[kraken]

Hi,

I have some sort of issues with the surface normal, even on simple primatives (like a cube or cylinder) . I've tried flipping the faces and it just doesn't resolve the issue.
Look at the surface of the rectangle. If I make a cube it has these strange radial markings (like anistropic textures). Is there any work around? I'm in the middle of a project.

Thanks

Notice the odd shading due to bad normals

[grimm]

We need more information to investigate this, either post the .blend or give us the details of the render. We need information about the versions you are running, your system details, what kernel you are rendering with, etc.

[kraken]

latest release.
Win 7 64b
3x GTX-690
latest drivers

The problem occurs if the material created has the "Smooth" check box ticked. If its turned off the renderings look right, but faceted.
I have other problems with now. Hangs on rendering animation. Writing a new bug report.

[grimm]

Ah, sounds like you have a normals problem, you should check them. The other issue just could be that you don't have enough geometry for the smoothing to work right.

[kraken]

Sure. User error.

Make a cylinder 32 sides. Add a material with nodes. Looks like junk. I'm sure its my fault.

Thanks for the help.

[grimm]

Sure. User error.

Make a cylinder 32 sides. Add a material with nodes. Looks like junk. I'm sure its my fault.

Thanks for the help.

Hmm, ok. Yes, it is your fault.

So I created a cylinder and rendered it with Octane:

It looks like junk. Now I bevel the edges to the cylinder like so:

Now when I render it, it looks better but still could use some more geometry.

The problem is not with Octane or any renderer, it's because the surface normals are being interpolated from one vertex to another. There are limitations to this technique and you have found them. If you want to understand better read up on Phong shading like here or other sites that talk about it.

https://en.wikipedia.org/wiki/Phong_shading

Now you can get shadow terminator errors which causes the edges of the shadows to be blocky. Octane 3 handles this better than version 2 so it will look better when the Blender plugin is updated.

[grimm]

Thinking about it some more, I thought of another possible fix, but I would need to test it more because I can't remember if Octane supports it or not. I think it does but I don't use this technique as much as I probably should. That would be to set an edge on the top and bottom of the cylinder. What this does is to split the normals across the edge so they don't get interpolated when the smoothing is calculated. This works really well if you want to keep the object low poly.

[kraken]

Thanks for verifying that I'm not insane.

I don't recall having this problem with other plug-ins. I have it for Daz and it works like a charm (well that is as long as Daz doesn't crash). I create objects in Blender and in Rhino and import them into Octane SA, no problems. I'm just an end user not a developer. I took a class at Berkley for computer graphics and ray tracing but didn't cover anything about normal or how to resolve this problem. I've found more problems so I'm starting to think the plug-in has issues. Like maybe the translation algorithm got transposed and flips half the normal around. I've tried manually flipping them edge by edge and it still looks like junk.

Why do these issues always occur right in the middle of a project!!!

James

[kraken]

So is this as far as it goes??? "Houston we have a problem"..."yeah so what, live with it."
I don't know about that. This is the best I can render with the plug-in. It has facets and if I use the "smooth" setting on the material it looks really bad. Nothing will make the facets smooth. Its not a blender problem. I'll settle for a work around if anyone has one.

Thanks.

[grimm]

If you can share the .blend file I can take a look at it for you.