Lights are Flickering

Watch the character on the left. The shadows are flickering like mad.
I’ve tried removing duplicate vertices to no avail.

Any other ideas?

I’m using ambient occlusion, some spotlights, and some area lamps.
Should I upload the blend files? They’re big.

Are you by any chance using shape keys on fairly large areas of the body mesh? If the surface is changing rapidly in small amounts it can be very visible at the shadow terminator.

It might be useful to look at the mesh frame-by-frame very close up and see if the vertices are jumping around a bit.

Yes, I’m using lots of shape keys.

The face was rigged with shape keys, and when his spine bends forward, I need to help his stomach bulge out with a shape key.

But … there’s lots of flicker on the top of his head, and the shape keys don’t affect that area

I’m not sure I understand why shape keys would be part of the the issue.
Also, how would I fix that?

Ok, so I looked up close. The vertices aren’t jittering.

Shape keys might cause a flicker if they are used over a large area and change rapidly from frame to frame, like on the twos or threes, just as can happen with very closely spaced armature keyframes. But much depends on the values in the F-curves and the nature of the shapes themselves. It was just one place to look.

If you can strip things down to just this model and its armature and the lights (maybe via an Append to a new file) and perhaps remove any texture data, it might make a file small enough to inspect easily. If the forum won’t upload it, you could use, which will take up to 20Mb.

I might try and strip this down and post it.

I noticed that the problem goes away if I switch my main spotlight from raytracing to buffer.
I may resort to this … but I’d have to re-do all of my lighting. Raytracing just looks so nice!

That’s a big clue! Have you tried adjusting the Spot’s specs (keep the raytracing – it does look great!)? Maybe switch from Adaptive to Constant QMC (or vice versa)? Another area to look at is the Material>Shadow parameters – Ray Bias (Auto or manual) is intended to prevent problems that resemble yours.

Looking at the lighting situation “as though it really were theatrical lighting on a real stage,” I would ponder that maybe the whole situation you’re trying to achieve is more difficult than it needs to be … especially given this is computer graphics, not reality.

The thought is (pardon me, I am by trade a computer programmer…) break the problem in half. First: “part (a) of the problem is easy … making sure that both characters receive an adequate amount of three-point light.”

Then, separately: “part (b) consists of achieving a nice interplay of shadows that conveys the characters’ shape as they are moving around.”
First, deal with part (a) by seting up the simplest (area lighting, etc.) way to light the scene. Then, deal with (b) by using (buffered, if you can possibly get away with it…) shadow-only spots to generate, in a separate channel, shadowing information. Now, you have two entirely separate “tracks” of information, perfectly aligned, that can be composited in (by whatever node network you please) to modify and/or to attenuate that original lighting solution.

In this way, the lighting solution no longer has to consider the detail-conveying shadows solution at the very same time, even though the two of them join forces to produce the final effect. Having generated “first one, then the other,” you can then “season to taste.”

I can’t deny that this approach seems “more|too complicated.” But . . .

Yes, I tried switching to QMC, and fiddled with the sampling # to no avail.

But … where is this Material option?

Still stripping down the bloody thing. It’s still to big lol.

In the Material context there’s a Shadow section, where you can tweak various aspects of the materials reaction/production of shadows. One of these is Ray Bias, intended to reduce errors on raytraced (Traceable) materials at the terminator, the crossover area between lit and shadowed parts of a form. It defaults to Auto but by unchecking this you can set a value manually.

I’d suggest that you should stop trying to “strip the thing” because … if you do somehow manage to “strip the thing,” it won’t be what you started with. It won’t even particularly relate to it, anymore.

Yeah, I’ve gotten it pretty small a few times, but then the problem would go away :-S

At what point in reducing the file size does the problem go away? That may be a clue as well. For example, if you remove the Materials and the problem doesn’t appear, then it seems an interaction between the Spot & the Material is a likely suspect. If it’s an interaction between Lamps, eliminating one or more from the rendering process should fix the issue.

I think it’s when i remove some of the surroundings.

I have AO on. Could it be the AO?

I’ve not seen AO cause this but that doesn’t eliminate it as a suspect. Try turning it off and see. It’s fair to say that the root of the problem is not really guessable since it seems tied up in your Scene construction as well as rendering specs, so getting to the root will be mostly a matter of elimination of possible problem sources.

If disabling AO does remove the problem, then next try adjusting the AO specs and see if there’s some factor in those values that contributes.

Oops, nope, it’s not the surroundings.
I’ve deleted everything except the character, and the problem persists. It must be the materials because that’s all that’s left.

Okay, here’s the deal. My my animation is in a linking file and my characters are proxy mesh. I’m trying to pull out all the links from my linking file, but Blender stubbornly remembers everything I’ve linked to. I right click on proxy objects in the outliner and sometimes I get an option to make things local, and sometimes I don’t. GRRR.

Anyways, as I’ve said, I’ve stripped down my scene to just the character. I’ve somehow managed to load in a local copy of my character. The problem persists … now…
If I change filepaths of my animation file, Blender doesn’t know where my textures are … and then suddenly the problem is gone.

Ok, now I’m really confused.

I have two copies of the same .blend file.
As far as I can tell, they’re identical other than that one has broken filepaths.

The one with broken filepaths works fine. The one with intact filepaths has the flicker problem. What could it be linking to? I link to some texture files, but textures are now removed in both files. All the materials are local as far as I can tell.


No, it’s not the materials.
I started back from the original animation file, removed all materials, and the flickering still occurs. I’m at my wits end here.

At this point I think I’d start reducing the Scene to bare minimums (only the character, the Main Spot, no AO or other environmental factors) by disabling renderability icons, then put various elements back into play until the problem pops up again. Wish I could help by digging into the .blend but I understand how the project’s complexity is a roadblock.

Okay… okay… both of you are now very close to chasing-down the same problem, but you (TwirlySocrates…) just might be running into the human constraint of “needing to stop and get some sleep.” :yes:

Whatever you do, at this point, be certain that you never “save on top of …” anything at all. Every time that you “save your work,” always choose a slightly different name, such that … tomorrow is another day … you can reconstruct what all the various differences actually were, and you can compare the various files one to another.


(Or:) If “the one with the broken file paths” does not exhibit the problem, and you have confirmed by some means “that this is so…” then, on the one hand, “this obviously could be a significant finding, because it obviously is a ‘bright-line’ difference,” but it is simultaneously a fairly ‘technically complicated’ difference, which immediately causes it to be suspect. I would not advise to put the full weight of my body upon such a difference until I had first constructed some sort of test-case that did not involve external files. Just sayin’ …

Don’t worry, sundial, I’ve never overwritten my original animation file.

chipmasque, what you’re describing is essentially what I’ve already done. I have one spot, and one character. Nothing else. That, and setting shadows to buffer fixes the problem.
Then, if I move the .blend file to a different directory, the problem goes away … presumably because a linking filepath was broken. But … I’ve already removed anything that the .blend file can link to. Hence my bafflement.

Buffer shadows are beginning to look not so bad :slight_smile:
I didn’t realize you could toggle buffer shadows for different objects.
The image still doesn’t look as vibrant, but it’s not too big a difference.

I’m rendering out the problem section with buffer shadows to see if the problem really is gone.

Okay, I’m going with buffer shadows.

I can get the scene to look pretty much as good, and it’s a bit quicker to render I think.

Wish we could have cornered that problem, but I gotta move on.

Thanks everyone for all your help and consultation :slight_smile:
If I ever get a file to properly isolate the problem, I’ll be sure to post it - I can do it from drop box.