Hi Guys!
I am working on a promo that will go on DVD and I am using the Non-Photorealistic Renderer for an animated walkthrough of a casino that has to be build in the future.
Because I will layer it with other material (stills with Global Illumination and video) I just use the outlines. When I render the image some frames render half or whole with broad grey lines from top to bottom.

I am rerendering it right now as sequenced tiffs, so I can try to adjust the individual frames. So I do not have an example at hand.

But has anybody seen this before?

I first thought I was crossing a bulb, in my animation.
The other thought is that I might be right on the same location as one of the lines, but maybe some of you have fixed this before I go all trial and error and get angry (Don't fear, I will not grow and get green, but I just don't like being angry).

Anybody?

I have no idea what this is. But I thought I'd reply so that at least you know someone has read your message. :-

I don't know what it is, either. But the banding effect almost looks like a toon artifact, where it's trying to assign 4 discrete colors to a gradient, as if there's some transparent surface or atmospheric effect between camera and the scene.

I could only conclude (from looking from the 'top' position, that I was exactly on a lie that I saw in the line preview mode. In the walkthrough, I ended up in the cellar of the building and then a couple of times only the hole from the stairs went black for one frame. It is strange. I editeted out most of this artefacts and multiplied the animation with a VectorStyle flash-version of the same animation. Layering video and rendered stills makes it a nice piece of video after all. But I hope Eovia will spend some time with the NPR to solve this things. I do not have enough time te experiment right now. Thanks for reading and giving it some thought folks!