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View Full Version : How to get dark AO in FG renders???


adrencg
01-27-2009, 12:49 AM
Let's assume that I know how to get a nice clean render with FG using HDRI.

How do I go about getting tthat dark, crack filling ambient occlusion, without resorting to the AO shader?

Is it all about the HDRi? What's the trick, or do I just have to make an AO pass?

bmwolf
01-27-2009, 02:30 AM
I think if you want the AO look, you're gonna have to use AO. Obvious options would be: plugged into the Ambient slot of all your shaders, a separate pass, or you can use the built in AO in the new mia_architectural shaders(my new prefered method). I'd be interested in hearing the other ways people use AO too.

Final Gathering alone could also get you similar results if you set the min and max radius really small.

adrencg
01-27-2009, 02:25 PM
I think if you want the AO look, you're gonna have to use AO. Obvious options would be: plugged into the Ambient slot of all your shaders, a separate pass, or you can use the built in AO in the new mia_architectural shaders(my new prefered method). I'd be interested in hearing the other ways people use AO too.

Final Gathering alone could also get you similar results if you set the min and max radius really small.

I usually shade a partition white, then plug the Ao shader into color. Then I take the frame sequence and use multiply in After Effects.

Lately, my FG renders are faster than my AO pass. I was thinking, if I could just get that AO look in my FG renders, I'd cut out a lot of render time.

CiaranM
01-27-2009, 03:27 PM
Try turning FG filter size to 0 for a start. Then increase your samples and lower your interpolation radius....then your FG renders will probably be just as slow or slower, but you'll get nice FG caching....

You can use FG as a rough AO replacement, just render with a pure white lambert surface with a white environment. But for the dark occlusion you want, you'll probably want to do gamma adjustments in post.

bmwolf
01-27-2009, 03:56 PM
I usually shade a partition white, then plug the Ao shader into color. Then I take the frame sequence and use multiply in After Effects.

I used to do it this way too. Didn't quite like the grain it could cause in the lit areas though.

Lately, my FG renders are faster than my AO pass. I was thinking, if I could just get that AO look in my FG renders, I'd cut out a lot of render time.

Yeah, Final gathering has really seen speed improvements lately. For some reason, I find the AO in the newer architectural shader to be much faster than the XSI AO shader. I use it in combination with final gathering/GI. You can use a nice smooth Final gathering solution then the AO built into the shader brings out the details. Only problem is you have to set it per shader, but it's just a check box and a few sliders. Could probably be done in the spreadsheet and you can exclude shaders that don't need the extra detail to speed up render time.

Here are some test renders using the above method. They have some artifacts because the settings weren't tweaked. Nothing special but the render times are very fast. Give it a shot.


http://bmwolf.zenfolio.com/img/v4/p1007567628.jpg

http://bmwolf.zenfolio.com/img/v6/p965586177.jpg

http://bmwolf.zenfolio.com/img/v5/p625969764.jpg

http://bmwolf.zenfolio.com/img/v4/p733082055.jpg

adrencg
01-27-2009, 07:49 PM
Wow, wolf, that stuff looks nice. That's the look I'm talking about. I can get that now, but with all of the extra hassle of my AO pass.

This method assumes that you use MIA material for everything. I know its great, but can you use it for everything?

I definitely think its awesome for metal and glass, and I've even used it for organic material in medical animations. I guess it could be used exclusively throughout the scene .... it renders fast and looks amazing.

bmwolf
01-27-2009, 08:35 PM
Yeah I use it for everything, but I'm usually not trying to fake specular highlights, or I'd use basic phong/blinn with ctrl_occlusion. Have you tried the new AO Caching or baking the occlusion using bent normals? I personally don't care for the former, the latter should give you a pretty significant rendering speed boost for a simple animation. It'll just take more setup time. I'll update with a link in a minute.

edit: Here's a link: http://www.harrybardak.co.uk/TDlove2006.htm

Oh and thanks for the kind words!

adrencg
01-27-2009, 09:06 PM
Yeah I use it for everything, but I'm usually not trying to fake specular highlights, or I'd use basic phong/blinn with ctrl_occlusion. Have you tried the new AO Caching or baking the occlusion using bent normals? I personally don't care for the former, the latter should give you a pretty significant rendering speed boost for a simple animation. It'll just take more setup time. I'll update with a link in a minute.

edit: Here's a link: http://www.harrybardak.co.uk/TDlove2006.htm

Oh and thanks for the kind words!

yeah, I tried caching the AO, but the results were horrible, even with much tweaking. I'll read that link. Thanks.

I like the MIA material AO. never used it. Looks good and is fast.

CoolCalb
01-29-2009, 08:29 AM
you can also add an AO shader directly to your camera..

in the render tree connect a mix2colors to your camera, on the base color, connect a
toon ink lens shader, double click it, and set the bypass on, in the color1 input, connect
an AO shader, and set its parameters, then just double click
the mix2colors, and set the weight to 1, and the mode to multiply..

This is basically like composting an AO layer over, for every frame..

adrencg
01-29-2009, 02:30 PM
you can also add an AO shader directly to your camera..

in the render tree connect a mix2colors to your camera, on the base color, connect a
toon ink lens shader, double click it, and set the bypass on, in the color1 input, connect
an AO shader, and set its parameters, then just double click
the mix2colors, and set the weight to 1, and the mode to multiply..

This is basically like composting an AO layer over, for every frame..

I actually used the MIA to shade a partition. I just set it to flat white, turned off reflection, AO set to ON, and make a separate pass to use in AE. I like the extra control I can get in AE.

It renders faster and cleaner than the basic AO node. Thanks.

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