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hexygen
06-04-2009, 08:29 PM
Hi all,
I have a noise texture in my scene with noise type = Billow.
I want it to change and "flicker" only when the camera is moving, so in the beginning of the shot I want it to keep still.
According to the documentation, you need to animate the time attribute for the noise to change:

Time is used to animate the Noise texture. You can keyframe the Time attribute to control the rate and amount of change of the texture. Typing the expression "= time" into the edit cell will cause the texture to billow when rendered in an animation. Typing "= time * 2" will make it billow twice as fast.

However, when I render a few consecutive frames with Time = 0 (and not animated) the noise pattern still changes a bit. It doesn't happen when I use perlin noise.
I also tried removing all randomness parameters (Density, Spottyness, Size rand and Randomness are all 0) and it still happens.

Am I missing something or is there no way to keep billow noise still?

I'm probably going to solve it by using an image instead, I would just like to know if there is a way to do it using the procedural texture.

Thanks,
Yanir

strange_quark
06-04-2009, 11:35 PM
if you are seeing some of the areas in the texture pop in and out, its probably low AA settings. esp with mental ray : small details can flicker or change from one frame to the next with less than min 1 in the AA.... it sucks, cause it could be slow to render...

hexygen
06-05-2009, 07:18 PM
Thanks doug,
I tried raising AA "min sample level" to 4 and it still flickers and changes even though the Time attribute is not animated.

It seems that this is happening only when the object / camera is moving, no matter how slight the movement is. It's easy to reproduce using a plane with the noise texture. When the plane isn't animated, the render is the same for all frames. I made it move 0.05 units over 24 frames and it started flickering...

It also depends on my noise settings. I am using high frequency and low density (< 0.1).
If I change some of the parameters the flickering stops but the noise doesn't give me the look I want.

YourDaftPunk
06-05-2009, 10:05 PM
When the plane isn't animated, the render is the same for all frames.

Is it 3d noise? Because if your object is moving, but the texture space is fixed, your object will appear to be swimming through the texture. (3D noise is not based on UVs) If this is the case and the object is animated but not deforming, you could simply parent the place3DTexture node under the object. You could also create a texture reference object- check it out in the docs.

Billow should be stable though.

-shawn

hexygen
06-06-2009, 01:41 AM
This is a 2D noise texture.

Parenting a 3D noise to the object is an interesting idea, even though it seems a little redundant since I already have good uv's for the object.
I'll try it anyway, maybe it will work.

YourDaftPunk
06-06-2009, 03:41 AM
Are the UV's changing during the animation? (Projected uv?) I cannot reproduce your error. You should upload an example.

hexygen
06-06-2009, 09:24 PM
The UV's doesn't change. I'm sending an example of a scene reproducing the problem with very simple settings.
I also added renders of the 3 first frames using maya software.

When the properties of the noise are different (higher density for example) it doesn't happen. I think doug was right and it has something to do with sub-pixel anti aliasing problem.

I eventually worked it out in my original scene by using rasterizer rendering with the highest quality and reducing the noise "Depth Max" attribute to 1. It reduces the flickering so it's not very noticeable in my comped since.

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