View Full Version : Flickering during render-Solution???

12 December 2006, 03:42 AM's the scenario. I have tried every trick I know of to get rid of some flickering of light during my animation. The offending geometry are the whites of the eyes of my character and my rim light striking his face and nose and flickering when he moves.

I know Maya offers many tools to correct this and this is what I have tried:

1) Check the shading samples overide flag on the geometry...I changed it to min:3 max:32. I maxed the shading samples out on that piece of geometry to attempt to get as many samples as possible per pixel.

2) Reduced my contrast threshold settings in order to have the max shading samples setting kick in sooner.

3) Used multi-pixel filtering set to Gaussian: 3.0 in order to reduce the flickering on the edges of some other tight geomtery that I have...but I figured it might help that as well.

4) I was going to use the edge anti-aliasing over-ride setting...but seeing as how the flickering did not occur along the edge...but on the face of the geometry...I did not think that would help.

The light I am using is a spotlight with depth map shadows turned on...and 'use mid dist dmap' enabled as well as 'dmap autofocus.' and resolution set to default 512. I did not think that either one of these settings would cause flickering becase there is no change in the scene scale during the duration of the animation, and no large objects ever obstruct the view of the scene. And it's not the shadow that's's the edge of the light on the face.

Now, my render dimensions are 500 X 500 and 72 ppi. I increasted the ppi to 100 thinking I might not have enough pixels in the scene to catch the detail in the eye. But that did not seem to help either.

Any suggestions?? I have tried all that I can think of...I am tapped out!!

Thanks so much.:thumbsup:

12 December 2006, 01:17 PM
What kind of flickering u are suffering?
I myself consider there are 2 type:
- Model flickering: just good AA and a gauss filter is good
- Texture flickering: That s it, when we have small texture, small bump, tiling small texture, procedural where far from camera ... all of them cause that stupid texture flickering...

01 January 2007, 01:29 PM
I was getting flickering where the edge of my rim light was hitting the tip of my characters nose and side of his face and eye. There was a sharp contrast between the bright light of the rim light and the darker side of his face that would shimmer between frames. I"ll upload a jpeg in a little bit to show you what I'm talking about.

01 January 2007, 04:35 PM
What kind of material is on the character in the problem areas?
I'm wondering how the specular reflection is being handled.

Have you tried blurring the edge of the spotlight? There are several techniques.

01 January 2007, 06:20 PM
Hey what's up. I have the character with-in the perimeter of the spotlight cone. It's a rim light that just hits the side of his's an image to show you what I mean.

During animation...when the character turns his head...there will be a shimmering on his face. Now I know that this is usually a shading sampling I tured on the override for adaptive shading on just his face.

shading samples: 3
max shading samples: 32

I was hoping that by maxing the adaptive setting that since it was such a high contrast area that it would kick in at just that area so I didn't have to up the samples for the whole face. But perhaps I need to increase the shading samples above 3...maybe to like 8 or something? I'm just trying to avoid jacking our rendering times up too much.

There is a layered shader on his face which contains 3 nodes:

1) A Lambert for the skin color and tone.
2) A Blinn for the flat highlight of his skin which has texture maps on bump, spec, and reflected color.
3) Another Blinn for the tighter highlight.

There is no raytracing in the scene and all the lights are spots. I was thinking of using an area light instead of a spot for the rim because the area light should soften the transition between the light and dark areas and help me not have to jack the shading samples up so much.

Any ideas would be greeeeatly appreciated.


01 January 2007, 03:01 AM
Seeing this, I'm going with ghostlake114's second item - texture flickering.

Since you are using it for both bump and spec color, and looking at it from a distance, they could conspire against you here. Are you using any filtering on them?

In addition, you said you put it on reflection color. Isn't reflection color for ray traced reflections?

01 January 2007, 03:52 PM
Hey thanks much mang. This character has textures mapped to the reflection attr because he's used in other scenes where raytracing is used. But in these group of scenes I have raytracing I would think that aspect of the tex shouldn't cause any problems.

I think I finally figured it out though. And I have found no documentation which lists this as a possible problem. But what was happening was that part of the face...and another piece of light which was shining on his left nose wing was so small I did not have enoug pixels in the final image to properly resolve the issue.

I cranking my shading samples on the head object to the max: 32 for the base shading samples and 32 for max shading samples but that still did not help. But it was because I had my ppi set too only 72 ppi. There just weren't enough pixels to resolve the shading...even though I had the samples cranked. So I increased the final res. of the image to 200 ppi...and once I did that there were enough pixels in the image for the shading samples to resolve nicely.

They should include that somewhere in the troubleshooting docs...because it didn't occur to me for the longest that the ppi might be an issue...untill I tried everything else, and that seemed the only logical answer.

Thanks much for the help though everyone. Much obliged. :thumbsup:

01 January 2007, 10:30 PM
Thanks for sharing your result.
Can you tell me where to find the shading sample attributes for the geometry? thanks
never mind, i found it. its under the objects shape node, under the mental ray tab., though i am still curious where you found the dpi setting. thanks

02 February 2007, 06:36 PM
4) I was going to use the edge anti-aliasing over-ride setting...but seeing as how the flickering did not occur along the edge...but on the face of the geometry...I did not think that would help.
....I realize you've already solved your issue, but could you elaborate on where this edge anti-aliasing override setting is? I can't seem to find it anywhere, and I'd like to try it on something

02 February 2007, 01:55 PM
Hey prob. Just go to the AE for the geo and under the 'Render Stats' drop-down you will see it. Hope that helps. :)

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