animation with MR-GI and/or FG


Hey guys, I just want to know if you ever made an animation with the Mental Ray GI and FG or only with FG, because I can’t believe that MR’s GI and FG are ready for production. I mean rendering hours on a single frame and still have some artifacts (with a lot of tweaking, too) isn’t very production friendly. Brazil for example, is not fast but it’s faster and the images are much more clean. Why is GI and FG includet in MR when it’s not very useful and production proven (maybe it is, but I don’t thing so). I like every byte of MR exept this GI and FG engine. OK maybe it’s just me and I am not as good as I though, but rendering hours, days or even weeks on an short animation can’t be normal (for high-standard studios maybe but not for a single PC artist).
I hope that mental images will improve the GI-FG part of Mental Ray in the next versions.
:cry: It’s damn disapointing…

Best regards,

Edit: Oh and if one of you ever made an animation with GI-FG/FG, is it at least completly flickerfree? (HOPE SO)


Does none of you has ever used Mental Ray for a movie or an animation with GI? Not even a testrender? I do, but I am stil trying to archive a non flickering, clean GI-animation with MR. Stills are easy to make clean, but if you have moving objects, lights and such stuff, it’s a real challenge.
Last night I rendered a short scene with some moving objects and GI+FG, but I don’t know if it’s the video codec or MR’s GI, but it seems to flicker. It took nearly 6hours to complete, because I used a high number of Photons and samples (100000 Photons and 1000 FG-Samples with ajusted raduis, because I have some small objects and a lot of small edges).
Any suggestions are welcome…

Best regards,


can’t help you with mray 'cuz i didn’t use it much… but i’m watching this thread… topic is interesting…

one way to see if codec is causing flickering is to render as tga sequence and play it in ram player…

hope that experienced people with mray will share some experiences soon… :slight_smile:


I also ran a test last night, and this morning I did see some flickering…my FG settings were low though (64 & 200) , so I bumped it up again and its rendering right now. I’m also not sure if its a raytracing problem cuz I’ve got some reflective glass in the scene. I’m also hoping that mr will handle an animation without flickering…I tried rendering an animation with Brazil a while back but it too had those problems.

But if mr was used in production for movies like the hulk and T3…why shouldn’t it work without these problems? Let us know if you’ve found anything new, and I’ll do likewise…


Try asking here… to the MR Guru…



Is there a renderer that actually does animated GI without artifacts? I thought they all did this to some extent (some worse than others).

Are you using the radius settings on your GI? That may help the accuracy but then you will need to adjust the amount of photons to balance the render times. Render times seem to increase when I use radius control.

Are you rendering out the frames and putting them together later or just rendering a .avi or similar? If frames, maybe ambient occlusion via dirtmap shader would work better for you?



yeah i’m making a short animation and really wanted to use FG but the rendering times jumped up to high so i rendered it without FG :(. I did think of using the dirtmapshader but what i really want is the colorbleeding and i don’t get that with dirtmap, not that i know of anyway.


There are renders which produce non flickering GI, Brazil does for example. But it depends on the way of calculating GI. One way is the view dependend GI-sample distribution, wich isn’t good for animations (objects, lights) only for camera moves. Another way is the iridiance-map, but I don’t know how it works really. And Brazil works with brute-force, which is ready for animation. MR works with a solution which distributes the rays from the light source (GI not the FG) which seems to be flickerfree, but the FG works in another way, looks like the way of distrubute rays depended on the view :frowning: but I don’t know really…


we’re doing some camera animations for a 3Dbuilding with the max light tracer at the moment in our office.
it’s doable for smaller parts, for the heavy stuff we texture bake the scene (no flickering and VERY fast renders.)
but then you’re very limited in animating things, we only move the camera… but for this project it’s more than ok

(you could texture bake the scene and have only for example a character animated an rendered live to speed up things)

no disrespect, but MR can be very fast, if you know the tricks
(same goes for the other adv render packages i guess)

but animating with these packages might not be the most productive process … it’s just not a very good idea if you have a small budget from your client.
no matter what program you use, they will always take a long time i guess… :hmm:


With some tweaking I finally got the rendertime down to about 5min per frame, not bad eh? I also noticed that for animations without artifacs you need a high number of FG samples but you need not many GI photons (depends on the scene, but 50000-100000 works very well for me). I haven’t turned on the GI radius, but for better quallity especially in the edges I turned on the FG max and min radius (also depends on the scene, but I had a very small radius in the min and a slightly bigger one in the max, because I have some very tiny edges). I thing that using both, GI and FG in combination with small FG min/max radius is the best solution for artifact free animations.

PS: (peekoot) the ram player doesn’t seem to open image seqences, it only opens single frames, or am I wrong? If I open the first frame of a seqence it does not let me choose the frame number, so it importes only the first one…but maybe I do somthing wrong…:hmm:

Thanks all for your participation and suggestions :thumbsup:



I’m currently trying to bake all lighting information including FG into textures. That way I got flicker-free animations. However this is only tested with small objects.

Couldn’t the flickering occur because the final gather map has to calculated again every frame? That would be my guess.


Originally posted by matlock
[B]I’m currently trying to bake all lighting information including FG into textures. That way I got flicker-free animations. However this is only tested with small objects.

Couldn’t the flickering occur because the final gather map has to calculated again every frame? That would be my guess. [/B]

offcourse ; you can save the photon map and fg solution.
so it can be reused when rendering again (sort of ‘texture baking’). this will save a lot of calculation time…
however : changing the camera will cause to FG sol to recalculate, so your guess is correct.

FG -> calculated from camera
Photons -> calculated from light sorces

your doing real texture baking with Mental Ray?
can you explain your workflow for that?
this could get intresting :drool:


Yeah texture baking is very good for achitectual camera moves, but I need a flickerfree GI solution for animations, not just the camera, but with characters and objects. MR’s features are outstanding (Displacement, Shaders, Caustics) but if you only use the GI without FG you can archive flickerfree animations, but it doesn’t look very good (not really realistic). You need to use the FG to get a smooth result, but because FG distributes the samples for every frame in a radom order, so it gets flickering :cry: There musst be a way (at least in the next release of MR) to archive flickerfree animations with FG.

BTW: Caustics work very well, without flickering, because it also let the lights emit photons :applause:


I already know about saving the fgm and pmap’s. And yes, I’m currently experimenting with real texture baking (save to a file).

This is how I did it.

  1. I edited my base.mi file and removed the “hidden” tags from lightmap_write and lightmap_sample.

  2. I made a simple box and tesselated each face once breaking up each face into four. Then I beveled the faces once.

  3. I assigned a standard material to the box and scrolled down to the mental ray connection rollout. I added the Lightmap Write to the Light Map slot.

  4. Then I added a UVW Unwrap to the box. And unfolded the UVWs.

  5. I rendered and it generated a texture file with my lighting baked.

There are a lot of problems however.

  1. You can’t see how long it will take before it finishes.
  2. The results are kind of blotchy and not really satisfying.
  3. It’s kind of buggy.
  4. You have to turn down the energy levels really low otherwise the texture will be “overblown” if you get what I mean. This is probably the biggest problem, because you have to change your settings from something that looks good in the render window to something that doesn’t.

I’ve uploaded the animation I managed to get. The results aren’t very good but at least it’s working.

I understand your problem. But isn’t FG really intended for stills?
Even you say that FG is calculated randomly. I think it is very hard to get flicker-free results. Maybe you can reduce the effects by increasing the radius? Have you turned on Jitter?


I was reading through the replies above, isn’t there any way other than texture baking to get FG flicker out. There has to be a way. This is a serious problem. If Mental Ray gives this kinda result, how come it is used in production especially when it has been used on movies such as T3 etc. etc. Is it their custom programming/shaders ?

There has to be a way…probably being overlooked…


I don’t know how studios work but if I were to work in a studio I would not use FG. I would probably fake it.


to Texlon: yes, ram player can play sequences of images… that’s the best thing about it… you just need to check “sequence” found in the bottom of the window when opening file… i’ve worked with tga and bmp format so far… and it works great…

to sachinb: they probably use GI and FG much less than we sometimes think they do… :wink:


I found a mh … easy way to get a flicker-free animation, I just turned to values up to the roof. I made a simple animation with some rotating boxes on a plane, a skylight and a direct-light. I only used FG with 8000 samples and a very small, almost tiny min/max radius. It took about 7-9 min per frame, BUT you know that this is just a simple scene, nothing special, so the rendertimes may go throuh the roof on more complex scenes !!
I thing that the BIG studios using MR, fake the GI/FG or use like me very high values, which results in enormous rendertimes, but rendertimes are not important for them, using 1000+ computer, each rendering a single frame, and … Ping! you have 1000+ frames per hour (if one frame renders 1h). Small studios or even single PC artists can’t aford such big renderfarms, so they need to work around (fake the GI/FG) or use other renders such as Brazil (which is able to render flicker-free animation with GI, faster than MR)

But I am not sure, so please share your thoughts with us, and post your ideas. then are we able to find a solution … maybe.

Best regards,
Leon :wavey:


the studios that use Mental Ray (Hulk, Panic Room, Matrix Revolutions,…) use ambient occlusion not GI or FG. that’s what I allways read on threads in cgtalk…:stuck_out_tongue:
I don’t know this for a fact, just read it hear myself…

nice tutorial about amb. occlusion here :


cebas final render stage 1 have a hyper global ilumination solution for rendering sequences without GI artifacts.

But I think, global ilummination render technic is a quite expensive even todays post production facilities.

So there will never be a button like “push here and get best render”. A good 3D artist must learn lightning technics wery well. even global illumination can render fast.