fine details not rendering correctly

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  03 March 2013
fine details not rendering correctly

I have a coil of small tightly wrapped wire and I have no idea how get maya (2013) to render it out nicely in mental ray. I don't even know what to call this problem to google search a solution. I attempted anti aliasing, but the render times get much longer and not actually solved, just a little better than before.

what I am trying to render:

What it renders out as:

anyone know of a tutorial I can look at to find the solution to this?
  03 March 2013
Set it to Production render at 1920*1280 and use Lanzcos?
  03 March 2013
What you're seeing are called "Moire'" patterns. At the resolution you're rendering, you won't possibly be able to approach the level of detail in your larger example. But this is a filtering issue, so you should be able to get a lot closer anyway.

Try rendering it with Triangle, Gaussian, Mitchell, then Lanzcos? Alternatively, you can leave your antialiasing low in the main Render Settings and just use the shape-node override for that object to have it antialias more, thus saving a little rendertime.
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  03 March 2013
thanks for the replies

The following renders were done in 1080p and with the camera at the distance the render will be taken from, cropped and not re-sized. These were the results:





Lanzcos with anti aliasing at 4

Lanzcos with aa at 5 and shading at 32 - 20 samples

lanzcos looks the best, until I put an aa on it beyond the default production setting but still has that moire pattern issue. My internet searches come up with very little information on moire patterns when it comes to objects.
  03 March 2013
You’re probably better off to create that sort of tiny detail with a bump/normal map and use elliptical filtering on the texture. You’ll end up with a lighter scene file and no need for crazy AA settings or Laczos/Mitchell filtering, which can introduce other artifacts as a trade-off to their perceived sharpness. I wouldn’t be surprised if the moire was less offensive too.
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  03 March 2013
you could try unified sampling... Brenton Rayner has a good write-up about it here:

then you don't have to worry about the filter methods.
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  03 March 2013
tswalk is correct, use Unified Sampling and raytracing.

And stick to gaussian 2.0 2.0
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  03 March 2013
I finally got around to trying out unified sampling. It removed all the terrible noise, but it didn't bring in detail. (maybe I did it wrong?)

^cropped from 1080p^

I am going to try a normal map instead when I got time and see how it goes.
  03 March 2013
OP seem to make use of ambient occlusion, perhaps his issue stems from incorrect settings for the ambient occlusion effect?
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  03 March 2013
I don't think you'll get much detail at that resolution. You simply don't have enough pixel for it. I'd increase the filter size even more and use something like Gause to prevent flickering if it moves around.
  03 March 2013
Originally Posted by Panupat: I don't think you'll get much detail at that resolution. You simply don't have enough pixel for it.

it should be enough... I mean the loose wires that are on the shafts show up, why not the coils? They are no thinner or thicker, just spun much, much tighter.
  03 March 2013
Those loose wire are visible because their shapes are being defined by occlusion/drop shadow which spans more than 1 pixel. Those fine details on the other hand, each lines are only a fraction of a pixel. Trying to get sharp details on those will only create moire effects.

Imagine you draw a bunch of lines with 1 pixel width in photoshop. Then, scale them all down.

What you should aim for with anti aliasing filter in this sort of details, is to reduce moire and prevent flickering.
  03 March 2013
To test what Pan said, use your current render settings, but zoom in close to the objects giving you the moire patterns. If there is a large change (shadow to illumination for instance) over the distance of 1 pixel or less, you're going to get poor results. Antialiasing may get it to work at the desired size, but at the same time it may reduce the detail you can see quite a bit. Notice the example images used in this article are at quite different sizes, it should be more enlightening. It's possible that using bump or normal maps would help, but the problem of cramming too much detail into a single pixel would still exist I think.
  05 May 2013
weeell, I finally got around to taking care of the problem after all the things I've tried and procrastinating on it while doing other projects. Making the wires larger, though I was against the idea because I liked them smaller, was the optimal solution to get rid of the pattern.

here is a final render of it.

Last edited by Muzan : 05 May 2013 at 07:58 PM.
  05 May 2013
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