animation with MR-GI and/or FG


Hey guys you can get flicker free animations out of mental ray if you set the final gather to use a map, just switch off rebuid press the button below and set up a file somewhere in your system and press save. first time i went into here i thought you had to find a pre-existing file but just name something and press save.

i have gotten rid of the flickering in my aniamtions buy simply doing this,

i tried to up the amout of final gather points to 1000 but that didnt help just took longer.
looked a little better

the scene i was rendering the lighting is set up and stays the same for the duration
the only thing that moved was the camera along the path

the render may come out a slight bit darker in the indirect areas but if you set the number of bounces higher like 12, 12 and total 12 or 18 then the darker areas will brighten up usually the default is 5,5 total 5.

i had GI switched off and used the exposure controls in the environment to globally lighten everything up.

after this frames were rendering on average 50 secs each on my laptop including FG
although its a small render for web 490x270…

give it a go it might be what your looking for.



imexp fg rebuilds anyways (even if you use map) once you move the camera or when an object moves in your scene, cause fg is calculated from camera view

you can do it with photon maps, cause they are calculated from lights, so if you move the camera your photon solution stays the same…

could be mistaken…, please give us some screenshots to illustrate your point Xeno ?


i cant show pics.
its a rendered png sequence (rgba)

anyways i was getting flickering in places (indirectly lit areas) in my test renders and ive set the things as above and in the newer rendered frames the flickering is gone or drastically reduced so im not sure why, it just seemd to do a better job using a map because everything is still except camera

the photon maps set up seems logical and you are probably right i was just explaining a way that ive managed to get better results and reduce the flickering in my PNG sequences,.

the use of photon maps creates the artifacts and is why ive switched it off
fg helps smooth them of course.

heres a quote from the mental ray 3.3 manual…
about merging several key fg maps
“This tool is helpful when rendering animations. Flickering is reduced with moderate computational effort if several key frames are rendered with final gathering saved to files”.
i didnt do this but may give it a wirl next time

if you look up final gathering in the mental ray manual for 3.3 it discusses using fg without photon maps

typically if you dont use GI or photon maps the indirect areas are darker, ive tried to counter that effect by using more fg bounces and adjusting the exposure scale in the environment panel. probaly adjusting the physical scale helps more than bounces

the manual also mention that FG is replacing the use of photon maps more and more.with some exceptions…interesting reading…might be a couple of years old now before ambient occlusion and other newer techniques have turned up…



this is only so if you have rebuild switched on i had it switched off (no tick in box) but a file specified.



If a filename is specified using the finalgather filename option, it can be loaded and used if the file exists. If the finalgather rebuild option is turned on, any existing file will be ignored, and all final gather points will be recomputed and an existing file will be overwritten. The default is on.


apparently if you increase the filter size in FG parameters it does some despeckling i may also try this next…
default is 1 , values over 4 arent useful…



Have been trying out your explenations, but where can I change the number of bounces?



ok just did a quick test (only fg with moving camera) :

you are right Xeno : unchecking “rebuild” will not recalculate when camera moves
(which sounded logical to me, but for some reason my previous tests ended up in showing the opposite… :curious: )
and it does give less moving splotches in de animation… :thumbsup:

but the use for the the map file keeps being very unusefull it seems… :
because whitout the use of the map file (and the rebuild unchecked) it does not make any difference does it? (fg map file stays in cache memory it seems)

only plus i can think of is that you can pauze the rendering from the animated stills and start again whitout having to re-calculate the first FG map for the cache…

i will try later on with photons + FG (mabey its different when using them also)

it’s more like the opposite imexp : you should try to get an ‘almost finished’ render using only photons GI then just add a little FG (not more than 25-200) to even out the last spotches

this will allow you to not only have less splotches, but render the same (or even better) splotch free images with alot less rendertime

people nagging that Mray is very slow usually make very bad (or non) photon solutions and then try to get result by using very high Fgather settings which only result in very long rendertimes

oh and by the post : you could export some PNG files to JPG to show them here on this thread :smiley:


oh and by the post : you could export some PNG files to JPG to show them here on this thread :D[/QUOTE]

sorry if it was renders that were mine i could show them but its work stuff (confidential design data) i dont own the IP in these images…its up to the owner i guess and they wont be reciving animations with flickering going on. once things are public domain (they use it somewhere like the web etc) this is another thing…

you have already run some small tests to see the differrence anyways :wink:


Rick ive since found that the number of bounces in the FG rollout may not really do a lot
there are other things you can do that will make more difference…at the time i just had the bounces set higer and posted that but i could probably set them back to default and still get less flickering.(havent tested this yet - have deadline approaching)

[i tested it back at 5,5,5 and it was fine ]
the FG bounces may be intended for when your using a HDR map …possibly

i have made the scene brighter slightly by adjusting the physical scale settings in the environment panel exposure controls (render the little preview window and upped the physical scale amount)

the example that ive seen of jeffs MR webpage i checked again, and he was increasing the photon bounces to lighten the indirect areas not the FG bounces, -my bad

since checking what the FG bounces actually do it seems that if you make thema higher number then the results are negligable (just adds time to render without delivering a lot of noticable difference…Fg does most of its work on the first pass according to FG section in the 3dsmax7/help/mr_manual.chm

possible alternative to this is to increase the FG filter size to 2 or 3 (not higher than 4) i havent checked this yet… as it looks like MR already has an internal de-speckler (flicker killer)which is on by default (set to 1) im guessing if you made it two then it would do more averaging and give a smoother result…

people usually already do this another way by blurring the HDR image (if your using one) a bit to start with so there isnt any sharp changes between pixels in the HDRI image in the beginning you will find most free HDR images are already blurred slightly.

GI photon maps are good for indoor scenes, mines outdoor (in open space) so a lot of photons would just bounce off into nowhere

the main thing was to turn off rebuild, but still use a map, as it seems it will build a map on the first frame and reuse it for the others…this takes out a lot of flickering just doing this. and its not re-calculating it all on every frame (where the flickering comes in)

this would make sense because if i was a large studio id be rendering out a background pass on the farm as one set of footage (not much moving other than camers) and rendering out the characters seperately so i could control and tweak them better in the composite later on…possibly

{random nugget}
Pixars website used to have a section “how we make movies” i havent looked in a while but it may still be there…generally they render everything in passes (like render elements in max)

I havent tried to use MR with the command line but there seems to be a utility that can merge FG maps, so what you would do is render out several keyframes where the FG map would be desirable and use this to merge into one FG map that you use for the renders.
seems a bit more of a manual approach but could save proccessing time.



check this out it may be more suitable for general scenes / animations as my settings were setup for the kind of scene i had, and i tweaked stuff later in combustion. the above link may prove more useful to a wider variety of scenes to get a good result without too much tweeekin…
helps explain FG setting a little better than me :wink:


another technique I have used is to render my final gather map using a spherical camera shader in the lense output. With that map saved I will set the final gater to use the map but to use fast look up. The results were clean with pretty low render times. 30min per frame for a fairly complex interior scene.


Did anyone of you get a flickerfree animation with GI, FG & HDRI Combined?
I made an animation with a pretty complex character animation with FG & HDRI
and I still got some flickering in cramped parts of my character after I used
A LOTS OF FG with HDRI-image (rendering time was about 30 minutes/
second). I also thought about using E-light plugin to get a real world lighting
because my character was supposed to be used in composition of real- and 3d-

Please give me some ideas about that how I could render my character with
some kind of a “HDRI” with short rendertimes… :slight_smile:

Somebody wrote that big studios use just ambient occlusion to render their
scenes? Is there any professional tutorials for using of Ambient Occlusion?


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