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Author Topic: problems with flickering  (Read 19728 times)

Kai

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problems with flickering
« on: September 28, 2011, 12:00:09 AM »
I have been using billboard trees with forest pro but would like to make the change to 3d trees. In my initial tests I've been having a lot of trouble. Fist of all, backburner consistently crashes on every other frame. Thankfully it keeps restarting and the render eventually gets done.

My main concern is how to eliminate flickering. I'm using 3dsmax 2012 with mental ray and Forest Pro 3.6. I'm using forest color to create variation on the leaves. I've followed the guidlines on the best practices chapter of the reference manual. Are there other recommended settings in mental ray to avoid flickering?

Thanks,
Kai

iToo

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Re: problems with flickering
« Reply #1 on: September 28, 2011, 12:08:18 AM »
Carlos Quintero
iToo Software

jonavark

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Re: problems with flickering
« Reply #2 on: October 02, 2011, 06:02:15 PM »
If you will post your Mental Ray settings I think I may be able to help. I use MR and have conquered the flicker problem. Once under control it is a very nice render engine.

Kai

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Re: problems with flickering
« Reply #3 on: October 03, 2011, 10:55:31 PM »
hey, thanks for jumping in, I was pretty sure I'm not the only one to run into this problem. I've been playing around with the sampling and final gather settings but there must be something I'm missing. I attached an image with my mental ray settings.

I'm rendering a forest with just one 3d tree model created in onyx and converted to an editable mesh. I'm using arch and design materials on the tree and forest color in the diffuse channel of the leaves.

The surface terrain is using a mr matte/shadow/reflection material.

I appreciate any advice you may offer.

jonavark

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Re: problems with flickering
« Reply #4 on: October 04, 2011, 05:11:05 AM »
hmmm.. first thoughts..

You have soft shadows precision multiplier at 8. That's gotta hurt your render time and may be overkill.
I get great results with it set at 1.0

Sample setting of 4-64 might be a bit high as well. I get good results with 4/16. 64 is the highest I would usually go.

Instead of Triangle I use the Mitchell filter.

In "Project Points form Camera Position" the FG points actually move along the geometry as the camera moves. Think of it as a spray paint can moving across objects. Paint particles fall on whatever the camera is pointing to.

In "Project Points along camera path" the points are kind of stuck to the geometry at specific sections along the camera path. this works much better for animated cameras but

Moving trees, or other animated objects will flicker because Mental Ray is only projecting points for "n" segments in your camera move (9 is the default). You can increase that value if you are rendering a lot of frames but if your camera moves a lot it isn't necessarily true that FG points will fall on the geometry at the right places.

If you are rendering a complex scene it is helpful to render the environment and objects that are not moving with the "Project points along camera path" method and render the animation passes with "Project points form camera position". Then, in order to reduce flicker you have a few options, like interpolating between "n" frames from pre-calculated FG map files, which you can do using the "Reuse" rollout of the render setup | Indirect Illumination dialog.

If you want to get a better idea of what I am saying here google for Master Zap's Mental Ray tutorials. There is a set of videos that he has created available at some of those links that will really help.

Happy to try and answer any more questions you might have.

jona

Kai

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Re: problems with flickering
« Reply #5 on: October 10, 2011, 07:35:07 PM »
Thanks for these great suggestions. Unfortunately I'm still getting flickering problems.

I'm trying to isolate the problem so I have disabled final gather and shadow casting. The flickering seems to be related to sampling. It looks like animated grain. How do people render animations of 3d trees without running into this same problem?

attached is a frame from the animation. you can see that the camera is at a high elevation and the detail of the trees is pretty small. If anyone has experience rendering aerial views of 3d trees such as this with mental ray, how exactly did you do it without flickering?

jonavark

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Re: problems with flickering
« Reply #6 on: October 10, 2011, 09:13:07 PM »
The only way to deal with that is high sample rates or blurring in post. I routinely have two issues when I render fields of plants. Final gather flicker and noise like what you have described here. Only solution is sample rate. That is.. if you aren't using geometry with lots of sharp edges or triangular polys. I was working with a custom object at one point, a wheat field, and it had a lot of triangular polys on the tip of the plant. I had to change that geometry to get it to work right. And then, I had to use a high sample rate to minimize grain.

You may be able to have some effect on it with the contrast controls but I think sample settings and filter type are the main controls that can affect grain.


Sometimes you have to minimize the grain on a pass the best you can and then add some grain to the entire composite to compensate.

Kai

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Re: problems with flickering
« Reply #7 on: October 24, 2011, 07:47:33 PM »
I am finally getting good results with Thorsten Hartman's render optimizer script:
http://www.infinity-vision.de/blog/render_optimizer

I used unified sampling with settings of:
min: 4
max: 256
quality: 3.0
cutoff: .05

If you try this, be sure to embed the settings in the file under the settings tab. Otherwise network rendering will not work.

My rendering time is still too long, (20-30 mintes/frame on my 6 core xeon workstation vs 40-70 minutes/frame on my older quad core xeon rendering machines) but at least it doesn't flicker any more.

I haven't played around too much with final gather yet. What has been working for me is using "from camera position" method, 1 file/frame, interpolate for 2 frames.

I will put it up on you tube today and provide a link. It would be nice to get some feedback from forum members on how to improve the rendering or even optimize it further to render faster. For now I am including the first frame of the animation.
« Last Edit: October 24, 2011, 07:55:38 PM by Kai »

Kai

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Re: problems with flickering
« Reply #8 on: October 24, 2011, 10:32:33 PM »
I posted the animation on you tube: interchange animation

There's definitely a lot of room for improvement, but trust me, it's come a long way. I'm curious what methods other people use for lighting a large outdoor scene. I'm basically just using a mr sun and sky.

I would love to hear any suggestions for improvement or even methodoligies of how to set up a rendering task such as this.

Kai


jonavark

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Re: problems with flickering
« Reply #9 on: October 26, 2011, 01:24:44 AM »
Looked good Kai. Very good. The little flicker in the lower right trees area must drive you mad! Some of the flicker on the pavement texture might be helped with contrast settings in mental ray.

I would love to know how you set this one up.
How much of it is 3D? How much Ram it used to render etc..

Kai

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Re: problems with flickering
« Reply #10 on: October 27, 2011, 05:29:36 PM »
Hey Jona, thanks for the compliment and suggestion. I usually leave the contrast at the default setting but I will try to tweak it and see what happens. I'm still pretty new to mental ray and have a lot to learn.

This rendering is part of a larger project. This particular camera view has 3000 frames (The you tube video is only 2300, I posted it before the animation had finished rendering). The rendering is divided up into layers that I render separately and composite in combustion. The 3d tree layer is the one I've had the most trouble with. It took a full week to render on 19 rendering machines. I really need to optimize it more! It uses 9.6 GB of physical memory and about the same amount of virtual memory. Pretty much everything is 3d aside from some of the details in the aerial photo and some some billboard plants.

I organize my layers as follows from top to bottom:
3d trees and ponds
striping
cars and buildings
road and bridge model
docks in the river water
dtm (digital terrain model)
river water

I've been rendering out to rpf files so that I can do some color correction by object and material id.
I'm curious if other people use this kind of a layered approach or would you just render everything together?
« Last Edit: October 27, 2011, 08:31:22 PM by Kai »

jonavark

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Re: problems with flickering
« Reply #11 on: October 27, 2011, 07:03:32 PM »
You are approaching it the best way. The only way to do it actually.

Some scenes are hard to split into layers. Those are the nasty ones.

1 week on 19 machines sounds about right. Don't feel bad about how hard it is. ALL renderers induce flicker from GI/FG calcs. It is the Holy Grail of rendering as far as I am concerned. I have even lost a few jobs because I simply could not get rid of the flicker in the time I had to deliver animations.

With your 19 machines you probably only spent a couple hundred dollars on power. A commercial render farm would have cost anywhere from $1500 to $4000. Imagine paying for THAT and then seeing flicker.

What I wouldn't give for a render engine that rendered animations exactly as I see them in stills. I am not alone in that wish.

I thought your render looked very good otherwise.

UR4208

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Re: problems with flickering
« Reply #12 on: April 20, 2013, 08:48:10 AM »
Hello Kai. I have a similar scene with both animated objects and moving cameras. My forest is flickering when animated. I'm using 3ds max design 2013 with mentalray and Hq plants 1 and 2 with color tint. Which mentalray render settings should I use. My resolution output shall be 1920×1080. I've also installed Thorsten Hartman's render optimizer with the same settings as yours.

Jørn

Kai

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Re: problems with flickering
« Reply #13 on: April 22, 2013, 03:39:40 PM »
If you have determined that the trees are flickering because of undersampling and not final gather, then use unified sampling at the highest settings you can manage. I've gotten good results with
min: 4
max: 256
quality: 3
cutoff: .025

This usually works for me at the expense of very long render times. I've also been experimenting more with a render pass/compositing workflow. You can minimize flickering with some blurring or rendering shadows separately and compositing on top of a diffuse rendering.

You also need to consider your final output. I usually output animations to windows media and you tube at no higher than 720p. video compression will hide some of the flickering that sticks out like a sore thumb in RAM player.

Kai