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serge
11-14-2006, 01:43 PM
I'll be making an animation of a town with cobblestone streets and squares. The camera will fly through the town. I did a very simple test cloning a stone 10000 times and made a testrender. In OpenGL you can clearly see the artifacts where the stones are far away. Unfortunately they also show up in the render.

Pic 1: Screenshot
Pic 2: render 3 x AA
Pic 3: render 9 x AA

Higher antialiasing makes the artifacts less obvious, but it's still there.

Does anyone know what's causing this? And more important, how to get rid of it without setting the AA to extreme levels?

iggy21
11-14-2006, 01:56 PM
other than some type of Post production blurring, I think you might be stuck increasing AA.

StereoMike
11-14-2006, 02:54 PM
If you have access to the beta forum, you could ask there...

Extent
11-14-2006, 04:01 PM
I don't really see this as being related to a beta at all, it seems a fairly classic example of what you use AA for. As the details get farther away the sample rate is too small to accuarately render them and you get a morie pattern, the two ways you can fix that (without changing the model) are turning up the number of AA passes or rendering at a larger resolution.

We were given extreme AA for a reason :p don't be afraid to use it for your final render. You may be able to better results faster by rendering at 2x resolution and lower AA, then resizing to your final output size, but with how small those stones get in the distance you'll still need to use more than low AA I would imagine.

serge
11-14-2006, 06:04 PM
I don't really see this as being related to a beta at all, it seems a fairly classic example of what you use AA for. As the details get farther away the sample rate is too small to accuarately render them and you get a morie pattern, the two ways you can fix that (without changing the model) are turning up the number of AA passes or rendering at a larger resolution.

We were given extreme AA for a reason :p don't be afraid to use it for your final render. You may be able to better results faster by rendering at 2x resolution and lower AA, then resizing to your final output size, but with how small those stones get in the distance you'll still need to use more than low AA I would imagine.
Great! 2 x resolution did the trick. The pattern is almost completely gone. It's good enough for me. Thank you very much!

Actually, upping AA can't solve this pattern-problem. I did a 35-pass render and the pattern is still there. Rendering double-sized (or more) seems to be the only way to get rid of it.

serge
11-14-2006, 06:06 PM
If you have access to the beta forum, you could ask there...
I know there are some interesting AA discussions going on in the beta forums, but yeah, it didn't seem beta related.

Extent
11-14-2006, 08:03 PM
There are other options you can hit to increase the quality of the AA, like turning off adaptive sampleing, using enhanced AA, maybe using PLD? not so sure on that last one, I've heard a lot of people are unhappy w/ the new mode, I use Fprime now so I never deal with it anymore. Increasing the resolution is basically the brute force method of what AA does.

Think of it as a multiplier. You have one stone that takes up one pixel of space on the screen and use 32x AA, that stone will get 32 passes to make it appear correctly. If you double the resolution (4x the pixel count) that stone now takes up 4 pixels of screen space, and each pixel gets 32 passes, effectively AA 128 passes for that single stone, except faster. That's not quite how it works but it gives the idea of how much you can improve things at higher res.

serge
11-15-2006, 06:14 AM
Well, I had tried about every AA combination and quality. I tried different reconstruction filters, adaptive sampling I didn't use (makes the pattern much more ugly), I tried 35 PLD, Enhanced-High, all without luck. Doubling resolution with low AA, and resizing it later on gives a very nice render, and keeps rendertime reasonably low.

BTW, after I rendered the double-sized picture I opened it in Photoshop and reduced the view to 50%: the pattern is still there. Only physically reducing the size by 50% got rid of the pattern. So, if I understand correctly, when I only reduce the 'view', also Photoshop-viewer is not able to render these small objects correctly due to object-detail per pixel.

serge
11-15-2006, 08:06 AM
BTW, I've opened a thread in the beta-forums regarding rendering at higher resolutions.

For the interested that have access: http://www.newtek.com/forums/showthread.php?t=59155

Extent
11-15-2006, 06:38 PM
I'm pretty sure that photoshop just uses a nearest-neighbor filter when zooming the view, that's why you get jaggies when using odd zoomlevels (like 33%) So when you zoom out to 50% it just discards every other pixel, rather than blending them together, which is what gives you the more accurate representation.

Exception
11-15-2006, 09:19 PM
The best AA you can get is using the old Enhanced modes in conjunction with the classic reconstruction filter. You will get triangulated filtering which is close to PS's Bicubic filters. The PLD modes are all similar to bilinear.

StereoMike
11-24-2006, 03:35 AM
sorry, wasn't meant like "This is nda related".
I wanted to say, that the new aa methods of the beta could help you (and after some tests with a similar object I would say, yes it helps.

Mike

Captain Obvious
11-24-2006, 04:40 PM
Depth-of-field can work wonders for moiré patterns like this.