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I'm trying to render a tyre tread using displacement. Things were going well until I noticed a stepping / stripe on the vertical sides of the displaced geometry.



I am using a 32bit tiff image for the displacement which has been slightly gaussian blurred. I've also tried 8bit tiffs and 24 bit pngs, all create the same stepping. The model is pretty well subdivided; it's just a flat cylinder 12 polys across it's width and 256 polys around it's circumference. I've doubled the poly count (24x512) and it doesn't help. Smoothing is on displacement and the accuracy is set to 64.

Does anyone know what's going on?

Great start as for the stepping issue I'm not too sure whats happening there but I have to say that stepping / stripe adds a touch of realism to the tyre!

Have you tried higher precision?

It may be a problem with the map not being large enough. You see that stepping from the individual pixels in the map. Perhaps if you double it's size and gaussian blur it again it might help. If you've converted this map from 8 bit to 32bit, you need to do the gaussian blur in small steps, several times to avoid a stairstepping effect.

thanks everyone. I'll try Mihai's method. I've only applied the gaussian blur once, so I'll re-try it multiple times. I'll also double the size of the map.

I've sort-of sorted the problem. I found that if I turn on Image Filtering in the bitmaps options then the stepping goes away. The side of the displacement become very dark but because this is a tyre, that's ok. I'm under pressure for a deadline but will try other methods later..

Whilst we're on the subject - is there any way to 'fill in' the displaced part of the model? I've cut the tyre and, obviously, the displaced part has a hole. Is there any geometry way of filling this in? Or will I have to fix it in post, as I currently am.

oz42 wrote:I found that if I turn on Image Filtering in the bitmaps options then the stepping goes away.

Oh, that's a must.

For the hole part, you could make the displacement map so there is no displacement at the very edge of the geometry, just a tiny bit so the displacement doesn't start from the edge but a little bit offset from it.

Thanks Mihai, I thought that might be the only way. Currently the map is repeated around the tyre but I may have to create a unique map for the entire tyre?