Flickering test log

Decided to start a log for tackling the Final Gathering flicker problem.


Aug 5
So I found more areas of flickering yesterday as I played my animation to potential employers (noooes!) lol. I am beginning to think it's how I set my SSS - will look into this.


July 31
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TAKE 6 | NGF_s002_q001_s001 (skeletal hand) 

Render settings: Freeze FG map (built based on every 10 frames)

No other changes (except SSS samples 256).

Rendering using Batch Render

Render time per frame: ~2 min
Results: Flickers.


TAKE 5 | NGF_s002_q001_s001 (skeletal hand)
Render settings: Freeze FG map (based only on frame 1)
Increased shadow rays from 12 --> 64 (but this was still flickering using command line)
Rendering using Batch Render

Render time per frame: ~2 min
Results: NO FLICKERING!! But less accurate FG. Ah well, worthy compromise!

Oh...em...gee. If this is what was wrong imma cry.

I'm using Maya Batch Render instead of command line rendering right now and there seems to be no flickering in the first 20 frames that have rendered. I noticed the FG map seemed to be recalculated for every frame despite having set it to Freeze under the render settings in the command line rendering feedback. Could this be it?!!!!!!11111 After days of throwing out renders?!!

If this works, I'll try plugging in the FG map I built every 10 frames for greater FG accuracy (instead of only using the first frame which might be sketchy). But I need to read more about FG - if I'm rebuilding every 10 frames, won't that show the flickering? Will have to test...

Still doesn't solve my problems for NGF_s002_q002_s001 though - I might try to build a map based on every 10 frames and see how that goes.

I got a bit sloppy with my testing though and changed too many variables at once, will have to go back and try to isolate the problem!

TAKE 4 | NGF_s002_q001_s001 (skeletal hand)

Result = still flickers just as much as the original...

Hmm. I am stuck........

July 30, 2011
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TAKE 4 | NGF_s002_q001_s001 (skeletal hand)
Render settings:

Ok well I've deduced it's the combo of FG and SSS (surprise) because there is no flickering when I render SSS without FG. I did intend to compromise but it really doesn't look nearly as nice without FG.

TAKE 2 | NGF_s002_q002_s001 (cellular)
Render settings:

Render time per frame: 8 minutes

Result: Lambert doesn't flicker anymore but SSS still does. Increased SSS samples to 256 but still flickers.

TAKE 1 | NGF_s002_q002_s001
Render settings: No change except I replaced the Blinn with a Lambert
Render time: ~3 minutes per frame
Result: It flickers in a completely new way! :( It looks fine when the camera is not moving, but once the camera moves, there is a ton of flickering... I mistakenly thought that swapping the shaders would fix it, as there is no flickering in NGF_s002_q002_s004. But I just realized that although that shot uses the same environment, there is also no camera movement.

Back to the drawing board. :(


NGF_s002_q001_s001
Turning off FG seems to have removed the flickering. Compromising time. :(

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July 29, 2011
TAKE 3 | NGF_s002_s001_s001 (skeletal hand)
Render settings: Freeze FG map, Set Optimize for Animation, Max/Min radius to 3/0
Result: Still flickers despite having a frozen FG map.

I am so confused... perhaps it's not the final gather?! Testing this now by turning off final gather altogether. I used a SSS shader like all of my other shots though, so not sure why this one is acting up so much. Wonder if it has to do with the Displacement...  Nevermind, SSS flickers in every shot... just varies in terms of how noticeable it is.

Next steps:
- remove displacement
- change SSS to lambert

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Sometime in June...

TAKE 2 | NGF_s002_s001_s001

Render settings: Increased FG Accuracy from 80 --> 200 (FG rebuild ON)
Result:  Still flickers, did not notice a difference.

TAKE 1 | NGF_s002_s001_s001

Render settings: Set to Optimize for Animation, Max/Min radius to 6/0.6 (FG rebuild ON)

Result:  Still flickers, did not notice a difference.

Will try to freeze the map next...

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RESOURCES

This guy's nightmare sounds all too familiar...

http://forum.mentalimages.com/archive/index.php/t-5325.html

But his solution in the end re: shadows probably isn't what I have. Will give it a shot if necessary.

Freezing final gather maps

Tips

Calculating min/max radius

Unsolved threads :(
http://forums.cgsociety.org/archive/index.php/t-506421.html

Try changing filter type
http://www.digitaltutors.com/forum/showthread.php?18801-SSS-Flickering-please-help-!

Support for my suspicion regarding scale conversion or radius:
http://forums.cgsociety.org/archive/index.php/t-684211.html

Particle depth

The linstep method of creating a depth map for nParticles doesn't seem to work for cached nParticles. The black-white shows up when you first enter in the expression, but once you change the frames it disappears! I guess it makes sense though because I'm plugging the rgbPP linstep stuff into the Runtime Expression, and if the particles are cached, then it's not really "running" anymore??

Anyway, Marc (my hero) came up with a different method of generating a depth map.
1. Create a depth render layer to generate the Set Range node.
2. Connect the Set Range node OutValueX (only x because only want one value?) to npCloudVolume - incandescence r,g,b

This works well with using the Measure tool to set up the Set Range oldMinX and oldMaxX.
I used Mentalray to render and used a UseBackground shader on the other objects.

Goodbye Hardware Render Buffer! :(

I should start creating a blog tag called "Marc is magical" or something. :)

Membrane deformation mask

Creating a mask to separate intra- and extracellular portions (a la Marc):

This is a problem I've been thinking about for a while, but only came up with very convoluted answers. Here is Marc's simple and effective solution:
1. Create a cube and position it so that it intersects with the undulating membrane
2. Select the cube, select the membrane > Create a wrap deformer
The cube should deform the same way as the membrane.
3. Render out the cube completely white and the membrane black - bring the mask into AE for tinting, yay!

This way I can also use the mask to tint the objects without having to mess with the light colours!

Degranulating mast cell animation technique

Marc's method of creating a cell with nParticles that emits nParticles. Gotta write this down before I forget! This will be used for my mast cell degranulation and also nociceptor releasing CGRP and substance P.

1. Create volume emitter, place inside cell
2. Add radial field in the centre to push nParticles out
3. Set initial state and delete emitter when have enough nParticles
4. Make sphere/cell a collide
5. Select nParticle,  particle collision event editor
6. Type: check off Emit, set number of particles, spread to 0.5 (90 degrees), turn off inherent velocity, Event actions > check off original particle dies
7. Add radial field (only connect to new nParticles created) to make up for lack of inherent velocity.
8. nFactor node > Change collide width scale to -0.5 so will show up a bit on the surface before dying
9. Apply surface shader to both vesicle nParticle and cell
10. Render out vesicle nParticle to get spots where it collides.

EDIT:
I kept Collide on for nFactor, but created an Exclude Collide Pairs (under nConstraint) for the mast cell so the nParticles can escape. I set the inherit velocity to 1 for Event Type, seems to work ok.

I am so excited... I love nParticles!!!! Must get this to work in my scene now. :)

Note to self: wobble settings
STR 0.75
Time freq 0.2