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Photon Problem


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Attached is a rendering of an interior space I have been working on. It is very blotchy, so I yesturday I posted the question of what I can do to fix it. I got a reply to increase the GI Photons. I tried that last night, increasing it from 10,000 to 65,000. However the thing ran for over 15 hours and it never even got past the photon emmition process. Anyone have any suggestions on GI photon settings and maybe radius settings for Viz 2005 MR?

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the goal is to have a good coverage of all the areas in your scene by overlapping photons. the overlapping will average the solution and thus filter out the detail you need.


so it's a matter of balancing the number of photons vs. radius size vs. rendertime to get good looking, but fast rendering images.


and this will be different for every scene you start, so there is no fixed ideal number/radius for the photons in your scene you're trying now


your render should look nearly finished using only photons GI and no fgather (turned off).

then just add a small amount of fgather to filter out the last splotches (not more than 2000 should be final render quality)

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keep in mind your number of photons is per light, so if you are using 10 lights

you will be sending out 65000 x 10 = 650000 photons... that might be a little to much :)

also try with all detailed meshes like chairs and vases and all hidden and all textures in standard default material (no textures or bumps) to test out the good light setup

turn of all the cieling and artifical lights for testing...


just to get quicker tests and see if the daylight is setup in a good manner to move on...


oh ... and don't use glass in your windows add them as a seperate layer in photopaint lateron, trust me : glass in the windows and GI solutions will not work... (at least not in mray)


more on that here : http://www.cgtalk.com/showthread.php?t=192954&page=2&pp=15


below 4 steps in achieving the photons you should get in ALL Mray renders

1-3 are no Fgather

only diff is the number of photons (1000-2500-25000)

in 4 i just add a little Fgather to smooth the toughest spots (or one would need a cazillion photons to do that )

note that 3 is not that different from 4 but no Fgather was used in 3

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the photons in the Global Illumination rollout below the enable check box is for the photons "samples" ("sharpness" if you like)


GI Photons at the very bottom of the rollout for Global Light Properties is the amount of photons


(i never change the first (samples) : didn't find any use for that so far...)

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Please describe the lights and thier settings....., overall dimensions of the scene (ground plane everything), the size of the room used in the scene and if you are using final gathering ect......... Joske is correct in his response, however I can think of a number of problems that would make this scene look the way it does and render as long as it did.


You also have a light leak at one of your windows, what type of shadow/s are you using & how was the window, jamb stop & sash modeled.


The more info the better the answer, with mental ray for sure.




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