GI flickering issues

[deathuman]

Hi,
I'm trying to render 3 scenes that use the Environment Fog and i'm unable to render in any way and "mode" a good GI for a scene that has the environment background and the animated character.

The only thing that has worked so far and that work well with scenes that doesn't use the Environment Fog was saving a Fly-throught at about 6000 subdiv and an Irradiance Map in Multiframe incremental mode every 5 frames. This work for a static background that hasn't animated characters or objects in scene but if i want to render the attached scene all-in-one there are big sploaches everywhere that feel like someone is doing some photographs...

I tried rendering with the Light Cache as secondary bounces every frame and didn't worked, i tried using Brute Force as sec. bounces and same result and for the Primary i tried every possible technique for a good GI in animation, like Multiframe incremental, Animation (prepass) all with "camera path", "time dependent" and "world scale" parameters enabled everywhere.

All of this has been tried with the DMC Image Sampler with different settings (first bad and then better for that type of image sampler bad i'm rather unsure...): First with the Nederhorst (sorry for mispelling if I do...) settings and so every subdiv at 1 and the quality based on the noise produced by the "adaptive threshold" parameter and the min DMC at 1 and max at 128 that produced the lowest render time. After that i realized that wasn't right to use the Nederhorst settings with the adaptive DMC so i changed the max at 50 and every subdiv of reflections, refractions and lights subdiv at something like 50 to max 150 and that produced a small better quality with lesser rendering time but in doing all this the GI was ALWAYS wrong.
I tried with the Irradiance Map at 30 subdiv and 120 interpolation samples and also for the DMC, 150 subdiv and 100 interpolation samples, the two with the Very Low preset.

I'm interested in knowing if there is a solution that doesn't involve making the character on a different "render pass/layer" as i'm doing know (but don't know really of to composite correctly the Atmosphere pass) also because splitting the 2 things produce a fine GI that doesn't flicker for the background but the issue is only limited to the character that will continue to flicker but in an acceptable way (also because we have to deliver this tesis on the 28th of this month so there's no room for improvement).

For the sake of knowledge i will attach (because the internet connection at school doesn't seem to collaborate) the scene with the GI issue and one video of the beauty and one of the rawGI pass.

Again, sorry if I mispelled something.

Regards,
Andrea Molino

-----
BEAUTY VIDEO
http://youtu.be/PKJkiz56-v4

[joconnell]

For character stuff, especially in an outdoor environment (where you have no roof or enclosed room for light to bounce around) it can often be easier to use brute force for primary, and light cache for secondary. you'll get a grainy result rather than a flickery one so it's just a case of turning up the brute force subdivs until you get a clean result.

[deathuman]

Tried but can't have long render times and that solution seems to increase too much my render times per frame.

[griml0ck]

I would render the bg separate if the cam is not moving. Then use a z-depth pass in comp to get the fog. You can mix it with some noise/smoke layers to get some breakup.

For GI settings i use these in 9/10 times:
irrMap for primary with medium animation preset, change it back to custom and change color and normal thresh to .1.
LC for secondary with 2500 subdivs for HD frames, you can use less for smaller res. Check "use LC for glossyrays".
The DMC will only control your AA unless your using BF, then you need higher dmc settings to get less noise in the GI.
If it still flickers with above settings you can use BF for secondary.
Remember to uncheck reflective/refractive caustics if you don't have any glass materials in the scene, that can help reduce noise.

If you still have flicker after this I would think it's something wrong with your light setup. Try looking at hdrlabs.com and use sIBL GUI/edit to get a light setup for vray from sIBL. That is the correct way to setup a scene, and with those settings above you should not get any flicker. Only thing you need to remember is to connect the input in the reflection slot to the refraction slot also in the environment settings. sIBL seems to not do that for you, and then you get black refractions.
If your trying to use 2k HDR images for GI it's going to flicker no matter what settings you are using. sIBL edit can help you create a small blurred version of your HDR for the GI and still use the high res for reflections/refractions.

Cheers J

[Dariusz Makowski (Dadal)]

Nothing is moving there except for the guy... Do it on 3 passes.

1 frame still for BG
animation of fog
animation for the guy.

Easy way to do it is to copy master 3x
set up

1 master as still BG
1 master as FOG with BG being a black surface shader, and the guy that walks is black surface shader - that give u FOG pass...
1 master as animation - create floor with shadow material to get shadows, hide primary visibility for BG and leave just the guy - hide fog.

After u do this u comp it like that

guy - normal mode
Fog - screen mode
BG - normal mode

Job done. should take u like 1-2h to render it...

GL.

[deathuman]

Nothing is moving there except for the guy... Do it on 3 passes.

1 frame still for BG
animation of fog
animation for the guy.

Easy way to do it is to copy master 3x
set up

1 master as still BG
1 master as FOG with BG being a black surface shader, and the guy that walks is black surface shader - that give u FOG pass...
1 master as animation - create floor with shadow material to get shadows, hide primary visibility for BG and leave just the guy - hide fog.

After u do this u comp it like that

guy - normal mode
Fog - screen mode
BG - normal mode

Job done. should take u like 1-2h to render it...

GL.

That's the solution that i'm going after, something a little easier so i'm rendering a pass of BG with FOG with Multiframe incremental pre-rendered (because this seem the only mode for not getting flickering) and a pass with the animated character also with FOG but with everything hidden except for the ground that is a Wrapper mtl and at last a pass with all hidden but the character and an override with a simple lambert material only for the Alpha of the character.

With this setup (that i know isn't completely correct) i lose only 2h for prerendering every five frames the IR and 2h for the LC Flythrought but then i have about 20-30min per frame for the BG and then 10-15min for the character.

But the question is: How is possible that there's no solution to such an issue? If i have an animated background how can i solve the GI flickering? There's no other solution better than split every animated objects from the BG layer? It's a lot of compositing working like this...
With these settings i've solved the GI flickering on the BG but my character is flickering and i don't know how to solve this issue so the thing is that i'm pleasing myself with this result but it's not what i wanted as a product of quality...

[Dariusz Makowski (Dadal)]

Hey

Ur sollution will not work and u just render 2x fog for no reason. The alpha u get from lambert material wont have FOG in it so its useless... Also use Surface Shader with black or vrayLight with black and 0 power since it renders faster...

Why do you want BG with FOG with incrementals? nothing is moving on animation as far as I can tell just render 1 frame of it... U dont need to separate ur character and the third pass to get alpha for him - just set up mask layer so it renders at the same time in settings...

There are sollutions for ur problems but u have more than 1 problem here and it would take time to render properly - remember rendering does not start and end on you clicking render and then magic happens u have to properly set it up and break apart...

are we talking about this video btw? BEAUTY VIDEO
http://youtu.be/PKJkiz56-v4

Thanks, bye.

[super gnu]

why not try my method using the "use irradiance map" checkbox in the vray material? actually dont know if this has an equivalent in maya....

just hide your character/moving objects and calculate flythrough lightcache/multiframe imap for the overall scene.


then unhide your animated geometry, and make sure you go through all the materials on your animated geometry, turning off "use irradiance map"

now set the imap and lightcache to "from file" and specify your saved files.


when you now render, the bg and static objects will use the saved imap, but the objects with "use irradiance map" unticked in their materials will use brute force GI, based on the static lighcache covering the surrounding geometry.

you get solid static gi on your scene and perframe brute force gi only on the moving elements.

you can control the quality of the brute force gi by either adjusting the imap hsph. subdivs ( which dont affect the precalculated imap) or using the gi subdivs multiplier in the object properties of your moving objects.

i apologise if the terminology doesnt match entirely, im a max user.

the only downsides are a) no gi effect from the moving object on the background and related to this, b) no nice gi contact shadow under your characters feet. this can be resolved by using ambient occlusion, either in the gi settings globally, or as a seperate pass.

[deathuman]

Hey

Ur sollution will not work and u just render 2x fog for no reason. The alpha u get from lambert material wont have FOG in it so its useless... Also use Surface Shader with black or vrayLight with black and 0 power since it renders faster...

Why do you want BG with FOG with incrementals? nothing is moving on animation as far as I can tell just render 1 frame of it... U dont need to separate ur character and the third pass to get alpha for him - just set up mask layer so it renders at the same time in settings...

There are sollutions for ur problems but u have more than 1 problem here and it would take time to render properly - remember rendering does not start and end on you clicking render and then magic happens u have to properly set it up and break apart...

are we talking about this video btw? BEAUTY VIDEO
http://youtu.be/PKJkiz56-v4

Thanks, bye.

Yes we are talking about that video. I'm rendering 2x fog because i have to deliver my tesis the 26th and im in a group with other 3 people working on this and really don't have the time to make more tests so i went for the easy to render and "to get the job done" way but i'd like to understand if there are other options like what you have suggested.

By the way, I don't understand what you mean by "lambert material wont have FOG" because i'm rendering the beauty of the character with textures and same lighting of the BG. I need the character to be lighted by the same light of the BG so i can't simply put them off.

In the last place i tried to use only a Still for that particular render but there was a mismatch of "moving grain" over different shots that have moving cameras and at last i had rendered the Alpha that way because it was not only fast but because i had Hair on the character that only get out that way: there wasn't any way for attaching a material ID to a vray Hair shader but putting a lambert over the Vray Hair Shader slot worked so far.

By the way i'm interested in understanding the "flickering GI" issue and your suggestion are appreciated but don't answer my questions.

[deathuman]

why not try my method using the "use irradiance map" checkbox in the vray material? actually dont know if this has an equivalent in maya....

just hide your character/moving objects and calculate flythrough lightcache/multiframe imap for the overall scene.


then unhide your animated geometry, and make sure you go through all the materials on your animated geometry, turning off "use irradiance map"

now set the imap and lightcache to "from file" and specify your saved files.


when you now render, the bg and static objects will use the saved imap, but the objects with "use irradiance map" unticked in their materials will use brute force GI, based on the static lighcache covering the surrounding geometry.

you get solid static gi on your scene and perframe brute force gi only on the moving elements.

you can control the quality of the brute force gi by either adjusting the imap hsph. subdivs ( which dont affect the precalculated imap) or using the gi subdivs multiplier in the object properties of your moving objects.

i apologise if the terminology doesnt match entirely, im a max user.

the only downsides are a) no gi effect from the moving object on the background and related to this, b) no nice gi contact shadow under your characters feet. this can be resolved by using ambient occlusion, either in the gi settings globally, or as a seperate pass.

This is really interesting, so i do what i've alredy done for the static objects (and so Flythrought LC and multiframe IR) and then yes, there is a "Use Irradiance Map" for the Vray shaders also in Maya (i've used Vray on Max and really there aren't big differences) and then what make Vray use the brute force for the "unchecked" objects? Using Brute Force as a secondary rays engine?

[super gnu]

no. simply unticking "use irradiance map" will tell objects with that material assigned to use brute force for their primaries. its essential to keep the lightcache loaded in the secondary bounce slot so the primary brute force bounce has something to reference. without this, the animated objects will come out darker than the precalculated elements.

[deathuman]

no. simply unticking "use irradiance map" will tell objects with that material assigned to use brute force for their primaries. its essential to keep the lightcache loaded in the secondary bounce slot so the primary brute force bounce has something to reference. without this, the animated objects will come out darker than the precalculated elements.

Ok I understand. I will try this as soon as possible. Thanks for the tip.