View Full Version : Flickering or rather noise in render.
04 April 2009, 01:40 PM
I have exhausted nearly every possible tutorial, thread and video I have on trying to solve this with no luck.
I am rendering out a scene, with a tarmac floor, when I playback the rendered frames, there is a very evident noise coming from the floor. Only the camera is moving, everything else is still in the scene. I have the following settings and was wondering if anyone could shine some light on this. Would really appreciate some light on what could be causing this.
Physical Sun setup with no extra lights, but I am using envblur with an HDR for reflections so I am using an advanced rayswitch in the MR environment slot with the envblur (with a spherical lookup for the HDR) in the default slot and the physicalsky in the FG slot.
Adaptive Sampling: 0/2
Filter: Mitchell 4/4
Jitter and Sample Lock on
Framebuffer: (In 2009 this has really confused me, I have it set to 16bit short, if I change it to 32bit Float I get loads of flicker and the whole scene is much darker??)
Gamma: 0.455 with simple lens shader connected with gamma at 1.
Accuracy: 800 (This seems high already)
Point Density: 1
Point Interpolation: 40
Secondary Bounces: 0
FG Map: rebuild for the moment.
FG Quality: 1
The asphalt texture uses a filter type of MipMap with a filter setting of 0.1
Video example.. the noise is mainly in the back of the image, the best place to see the noise in question is to the left and right sides around the Torus.
LINK (11MB Right-Click Save Target As) (http://www.cgfolio.co.uk/cgtalk/flickr_1.mov)
Here's the sample scene too if anyone wants to have a look. You will need to reconnect the texture files and the HDR in the envblur section.
LINK (http://www.cgfolio.co.uk/CGTALK/noise_scene.rar) (33MB Maya 09 file)
I'm 99% sure that this is a shader issue. I am currently trying to improve the grainy/noisy effect by adjusting the reflection samples and then also comparing the result to adding interpolation in the shader attributes... the interesting thing is that, the areas of the texture map that seem noisy also show the same effect when I scrub through the animation in the camera view.. which leads me to ask, is it possible that the texture noise level in areas is too much for Maya to compute?
04 April 2009, 03:26 PM
Hi vfx, as you guessed, FG quality 800 at density 1 is way too much. I would say 64/0.4/32 should be more than enough for your scene. As for the noise, I believe it's because of the very low MipMap filtering value (0.1). Try Quadratic 0.5-0.8, or MipMap with elliptical filtering.
all the best
04 April 2009, 03:41 PM
Hey kostaz, Yeah those settings were used just to proove this wasn't related to poor FG settings :) Thanks for the tips, I have come across those pointers before, and I believe the issue with using other filters is that I loose detail.. I'll give it another shot and post back.
Update: Strange thing happens when I use Elliptical Filtering.. the texture gets way over exposed and looks very washed out... very white. Anyone know why this might be?
04 April 2009, 10:20 PM
I have found an answer, but its not very sensible.
If I change the Render Global filter from Mitchell to Lancozs, and reduce the AA contrast from .050 to .030 I remove all noise.. BUT, this isn't exactly sensible as this means that the same settings will be applied to all other elements in the scene increasing render times ten fold.
I can't use Elliptical filtering cos it turns the shader a faded white, and I can't use Quadratic filtering as it takes away all the detail.
I would really appreciate it if someone could tell me how I could fix this on the texture side not in the Render Globals.
04 April 2009, 10:06 AM
Should be good to set the Contrast on a per object (or per texture) base, but I don't seem to find there in the overrides. You could make a layer for the object with this override instead.
04 April 2009, 07:16 PM
Have you tried switching off filter type for the texture map?
04 April 2009, 11:34 AM
I would never go with Mitchell filtering (it looks nice and sharp in a still image but not in the animation) rather use Box or even Gauss (which softens the image which can be sometimes desirable). min 0 max 2 with contrast 0.1 or 0.05 if needed
You have several options for removing the flickering:
1) mipmap texture filtering + eliptical filtering on (easy set up in Maya 2009, or custom shader network needed for older maya versions)
2) double the size of the image (render bigger res and downsize then in compositing app)
Its pretty natural in real footage that details are gone with distance / camera or object movement so its not uncommon that one need to soft the renders anyway...regarding antialiasing algorithms
04 April 2009, 11:34 AM
This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.