Severe banding problem

[Gerry]

This is the model of the laptop I've tweaked and I'm working on animating a tutorial about pixels. This is a plain rectangular shape colored flat gray, with one light on it.

 

As you can see, I've got a pretty severe banding problem. Compounding this is 1) I wasn't having this problem yesterday, and 2) It seems to be getting worse in the course of the day. Earlier today, my renders would start with the banding, then it would smooth out by the end of 16 passes. Now, even with 25 passes it's still somewhat visible.

 

Any suggestions are welcome.

 

Gerry

[MattWBradbury]

First thing I noticed in the image is that there isn't any visible indication that you used Multipass (The edges on the side of the lap top are aliased).

 

What type of light are you using?

 

Are you using Z-Buffered shadow?

 

Is the material on the lap top?

 

The banding appears to be perpendicular to the light source, so there could be a problem with the intensity of the light. What is the Intensity of your light?

 

A choreography setup would be nice to see.

[Gerry]

Hi Matt -

Yeah, I used anywhere from 4 to 25 passes. This image was just one pass to really emphasize the effect but I can't get it to go away completely. The odd thing was that as I watched the render, some passes would smooth out the surface but the banding would be reintroduced on the next pass, fading in and out on each pass.

 

I have one rim (spot) light, white at 100%. The cone is pretty wide because of the way the scene has to be lit. It was at a fairly oblique angle for this shot and I moved it up, which helped a little. There's also a fill light behind the camera and pointing away, because I dragged it there to get it out of the way, but then I found it's filling the shadows just enough so I left it there.

 

Z-buffered shadow: Don't know. I'm at home now so I can't check but I will tomorrow.

 

No material, just a surface color, as well as ambience and specularity. The white text is a decal with an alpha channel.

 

Yeah, the banding is definitely perpendicular to the light source. I think that's a clue. Light intensity is 100%

 

I'll post a chor setup tomorrow.

 

and thanks for the look!

[John Keates]

This could be a shadow bias thing. Try raising the bias value.

[Gerry]

I think my one light source was at too oblique an angle to the surface. I shifted the light up slightly and the banding was still visible but it now vanishes with successive passes. Using 16 passes solved the problem.

 

thanks for your input gentlemen.

 

Gerry

[Gerry]

Here's a first draft of the final movie, and at 16 passes the banding is still evident in the opening closeup. I've got a little "roughness" in all the other surfaces of the laptop and didn't put it on the top surface of the cover because it was too distracting. But I may go back to that and just lower the settings.

 

John, I haven't looked at the shadow bias settings but I will now.

 

 

Edit: I'm also putting up the prj file in case you want to play around with it. Plus you get a free laptop model!

[Drakkheim]

Check to see if you have a double surface on that part of the laptop.

 

ie, 2 patches sharing the exact same space.

[Gerry]

Hm, this is interesting. The banding seems to have been a problem with the default light. No matter where I moved it I got banding perpendicular to the light source. So I deleted the light and created a new light, same settings, and the banding has completely disappeared.

[MattWBradbury]

lol, that's sad because that is what I wanted to tell you from the beginning, but I didn't know how many actions you already had for the light. Sometimes lights get it into their heads that they need to do some crazy stuff in order to look correct.

[Gerry]

Hah! I had a similar experience with a hair material last fall. It misbehaved and misbehaved until I finally deleted it altogether.

 

It was clear that the banding was perpendicular to the light but I never tested that until I'd run out of other ideas.

 

Thanks Matt!