GI and light leaks

[SgWRX]

ok, so i've seemed to find one solution to light leaks between the floor object and walls object. set the maximum sampling radius to a size smaller than the thickness of the wall.

 

if i have a cabinet which is made with one box, then several shelves in it that are separate objects (boxes for example), is it possible to get leaks above and below... no probably not right b/c the shelf intersects the geometry of the cabinet?

 

finally, i see where some talk about using GI + FG in order to help solve light leaks. and if rendering an animated camera (walk through) is this why you use every Nth frame - because you have FG which is camera dependant? (well, i read FG was and it seemed that way to me when i calculated it with one camera and then switched to a different camera and rendered again using the same FG solution).

 

thanks.

[Jennifer]

Hi,

 

Yes, FG will clean up your GI issues; that was its original purpose, as I understand it. It works pretty well by itself, especially for outdoors, and with GI for indoors.

 

If the objects intersect you shouldn't have any issues. This is not like Radiosity, where the geometry had to be seamless. You can use the Arch$Design material and the Ambient Occlusion option, or use the AO shader in a material, if you need to refine the dark creases of your cabinet.

 

Calculating every n-th frame allows you to Save the FG to a file, and then Freeze the solution to cause the rest of the rendering to skip the FG processing. You can save the GI, too.

 

http://www.max3ds.com/Download/mental_ray_101.pdf and http://www.max3ds.com/Download/mental_ray_102.pdf

 

Yes, the calculation of FG is view dependent, whereas GI is not. As long as you get enough of the views covered in your FG pass you'll be fine switching to another camera, but I wouldn't bet on it. Worst case it would be averaging FG points that are pretty far away from one another, and you will see some odd indirect illumination as a result. Can't hurt to save the FG from those vantage points, too.

 

Have fun!

[SgWRX]

having fun! thanks for the docs.

[Jennifer]

Ya gotta have fun.

[SgWRX]

jennifer, nice documents. one aspect i liked were the little explanations such as what physical scale does - it brings non-physical based lights up to scale. i've not read that anywhere else. another example was the gamma settings for bitmaps. although i'm deep-deep into digital photography & printing, it's not translating well for me in 3ds max. probably just terminology. but i've got to cross over soon if i'm going to get consistent results!