Splotches in the rendering - Mental Ray or Final Gather or ?

[brianheagney]

Hi, so I'm having an issue that I think I resolve every job, but it keeps coming back, and my prior solutions end up not working. I'm hoping that this image I upload will describe it best:

 

[ATTACH=CONFIG]45265[/ATTACH]

 

I am using 3ds Max 9

I am using Mental Ray for rendering

I am using Final Gather (settings should show up in the image)

I am rendering out a 320x240 pixel image, and enabling the read/write Final Gather Map.

After that rendering, I click on "Read Only (FG Freeze)" and render out a 3200x2400 pixel image (these images are usually blown up very large for marketing displays).

 

I do that because I read on this forum a number of times that rendering out a small image with the read/write final gather map, and then freezing it and rendering out a larger image will be fine.

 

What I'm finding is that when I render out the smaller image first, I get these weird dark splotches on the corners of my walls. But when I render out a much larger image first, the splotches are not present.

 

Does anyone know what the deal is?

[Justin Hunt]

Max9 was awful for those artifcats, they got better in Max2011.

 

On a side note generating the FGM @10% of the final res is too small, 50% is OK. If you really want to go so small then increase the density to get a good level of lighting detail.

 

jhv

[brianheagney]

Hey thanks for the quick reply, it is indeed a Max 9 thing, as I tested it out on a different machine with a newer version of Max. Thanks for the quick reply.

[marius e]

Tips for that image:

 

FG density-2

Rays per fg-150

Interpolate over nr-30

 

With those settings you will probably have the same quality but render a hell of a lot faster, and dont even need to save the map then, just render it out.

 

I also see that you have GI enabled, dont even think that you need that, you can rather play with your exposure settings to get dark areas lighter, and or up the sky light if you using one.

[Francisco Penaloza]

If you are rendering a image like the one that you show here, GI(Photon mapping) it is not need it at all, GI it is very useful for complicated interiors scenes with poor lighting, but Final gather can do most of the job by it self.

Now those splotches seems to be GI actually and not FG, as mentioned by Marius your values of FG are way exaggerated, give you specific values of FG it is difficult because this willl vary depending of your scene but as rule of thumb FG values should be around

FG density: 0.1

Rays per fg : 150- 200

Interpolate over nr: 70 -120

 

for over size images with small PC it is recommended to save a small version of FG but don't go that low, this will give you muddy results.

 

Not to brag about it, but time ago I wrote an explanation of the main components of Final Gather, take a look and you'll see what values work better for you.

http://www.evermotion.org/tutorials/show/7955/final-gather-tutorial-introduction