Final Gather Issue

[gilmog1]

Hi all,

So im round to rendering out my car and i want to do it with HDR images, ive created my own one in terragen using the HDR plugin, moved it to cubetocross then to HDRshop to create my HDR image, once imported into maya i then get some strange photon artifacts on my car as shown in the pic below. ive upped the final gather photons to 1000 - still the same, global illumination and enabled photons on the image but still the same, if i use a premade one from the interenet say from Debevec's site they work fine straight off, could anyone point me to how to get rid of those artifacts as i would like to use my own HDR image.. thanks..

[DjVoyager]

Check out these videos on Caustics and HDRI;
http://www.digitaltutors.com/chit_chat/showthread.php?t=238&highlight=caustics

http://www.digitaltutors.com/chit_chat/showthread.php?t=237&highlight=hdri
Let us know if it still shows those artifacts.
Btw, nice car :).

[Jak_Carver]

try increasing your FG filter setting, usually works for this specific problem. Also, i think your getting thrown off a bit in formation wise. FG doesnt emit photons, thats GI. Seems like something small i know, but MR is an unforgiving renderer that chews new people up and spits them out. try doing some reading on MR and alot of research just so u make sure you get as many details about it and how it works. a few hours of reading can save you a couple weeks worth of headaches down the road.

[gilmog1]

Voyager, thanks soo much for those tutorials and thanks for the comment on the car :), the vids gave me more of a view into the whole Mental ray system but didnt cure the problem, funny though because in the caustic video the artifacts Papa is getting to begin with looked very similar. Jak, once more you done it again bud :) i knocked the filter setting up to 5 just to test and they dissapeared on the first render :) any ideas what the sweet spot on the filter setting should be. i didnt notice any increase in render time so i may leave it at 5 for now. so now the car looks great but it could look better, Im going to try adding the GI and caustics into the equation see if i can get it looking even more real. thanks guys :)

[barryk50]

http://www.interstation3d.com/maya/tutorials/mray_thegathering/indoor01.htm

check out this tutorial it will help you with your GI issues. Not only do you have to work with the filter, you also have to experiment with the global illumination accuracy and radius. These two settings along with the photons emitted and the exponent in your light settings will make your render look a lot better but also increase your render times. Also, there is not realy a 'perfect setting' for you because every scene is different. It all depends on where the lights are and how much geometry there is in the scene.

[Jak_Carver]

well he was having Fg issues not GI issues, at least until he uses GI with FG then it gets fun lol.

Anyways, Mental Ray is a great renderer but you gotta treat it nice, like a well...actually im not going there that will cause one heck of an argument with the ladies here :P Have fun experimenting with Mental Ray and it's awesome features. As far as the FG filter goes, depends on how your scene is, each scene is as different as a finger print, so one must fine tune the scenes lights, GI, FG, etc. to get a good result; getting great Mental Ray renders is an art in intself. Goodluck, and feel free to ask if you get any other problems.

[wdaniel]

i had a simular problem. look at this thread i started at cg talk.

http://forums.cgsociety.org/showthread.php?t=325816

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