View Full Version : help with "crawingl" pixels on instanced forest

01-10-2013, 09:46 AM
Hi, I'm working on a shot right now that involves a camera flying over a forest. (I usually make molecular science animations, so this is a bit outside my comfort zone :) ) I've instanced a bunch of trees, and got the render looking the way I want, but when it moves, the trees in the bg have crawling pixels (due to the high level of detail in the instances, I presume), and I'm looking for advice to clean them up. I've tried various combinations of adaptive sampling, but it doesn't seem to be getting much better. I feel like I'm flailing. If the camera were not flying, I'd replace the background trees with lower detail models, but the trees in the foreground move into the background, so that's not an option.

Can anyone with experience with a shot like this make any suggestions as to what settings to try?

Thanks in advance!


01-10-2013, 09:57 AM
Double, triple resolution, then resize back in Photoshop..

01-10-2013, 10:33 AM
Yup... its an AA issue. Either render over resolution and scale back down in post (hijacking 2D resampling)... or check this fella for optimising LW AA http://www.youtube.com/watch?v=UgNB9tZWUmM

01-10-2013, 04:11 PM
Apart from what the others have suggested you can also try to fix it in post ... NeatVideo is very good with this sort of thing but as with anything that's post it comes with its own set of issues & approaches.
Here's a test I did a while ago with LW instanced grass and no AA - then the result after running it in NeatVideo (these MOV's are quite compressed mind you)
From what I remember there's a trial you can use to test things out.
There were a few threads here that mentioned it & how to use it so hopefully you can find them. If not I'm here to lend a hand if need be.

01-10-2013, 04:44 PM

Thanks for the replies!

Sensei, I've tried increasing the render size, but the problem is still there (although to a lesser extent) The render times have gotten a bit out of hand as well, but I'll keep trying. RH, I have re-watched that video, and will probably watch it a few more times. It is very helpful! Finally, adk, your example clips are quite promising. I will check out NeatVideo asap.

I'm sure some combination of these things will get me to where I need to be. I'll let you know how I make out.


01-10-2013, 05:11 PM
If you're using floating point format for storing image data, and GI, so RGB can exceed 1.0 value per channel, try using limiting HDRI range.

01-14-2013, 07:53 AM
So I've been playing with this over the weekend, and I have to say, Neat Video is amazing! The other solutions worked, but always at the cost of longer renders. With Neat Video, I was actually able to lower all my settings, and still get clean results. Of course, now that I'm saying such good things about it, It will probably betray me... :)

01-15-2013, 04:01 PM
Considering what you put in & what you get out, yeah it does an amazing job. It does have issues tho at the frame edges at times so you might need to render larger & crop in to the desired final res. (Liberty ubercam is perfect for this)

Not sure how you're going about your settings with NeatVideo, but what I found works best in this instance is to define your region to analyze, auto profile, then trash the settings that come up.
Then in Noise filter settings set the drop down to No Filtration. I know that sounds counter intuitive but it works like a treat.

Erikals describes this technique here (around the 4min mark) ... shame that the linked forum thread doesn't work.


01-16-2013, 02:11 PM
Yeah, that's basically what I did. The interface looks a bit different, but I just went through the motions of setting up the auto profile, then turned the sliders down to zero. I think it's just the temporal filter at work now. It works well, though :)

For the benefit of anyone who stumbles int this thread later, Erikals Youtube link should be: http://www.youtube.com/watch?v=-zV7wHlPo38 which is the first in a series of three about noise and reflection blurring. You linked to the second one.
No worries tho. :) Thanks for your help.