How to use DOF / Z pass to mask AO in an outdoor scene

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1

Hi,

How can I use the the Z pass to mask the AO pass only to objects near the camera?

Thanks

2

Using a normalized depth with a color ramp you can mask in z, them multiply the AO pass. Also works using mist pass and it’s better on very large scenes.

Depth:

depth
depth1920×1080 899 KB

Mist:

mist
mist1920×1080 886 KB

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3

Thank you. How do you mix it back into the final without multiplying the background / darkening? That’s the crux where im stuck. I want to apply AO pass to outdoor scenes, but every which way i go about it it the background is darkened

4

Invert the color ramp in that setup and change mix mode to Screen. Then you multiply over your final image. Think about the math, if you have a pixel of value 1,1,1 multiplied by any other, nothing will happen. For a pixel of any lower value than 1 multiplied by any other one, the final output will be a darkened pixel.

screen
screen1920×1080 932 KB

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5

Thank you. I think I got it. Does this look right to you?

blender_kTsA8r4CGP
blender_kTsA8r4CGP2069×1427 399 KB

6

Looks great. Keep it up! I believe you’re adding the mist pass to build atmospheric, you could also use a low density volume linked to a noise texture to be a more organic atmosphere.

7

Thanks. For some reason the math wasn’t mathing. I read up how screen works. I still don’t fully understand why it works, but I think I’m starting to get it. I understand we’re multiplying by 1,1,1 at the beginning. I think if there was a text descriptor of the math operation happening that would be helpful on the nodes. Like a tooltip or something.

Yes, I use volumetrics sometimes. I have high poly scenes (lots of plants, even though they are linked instances). I find the mist pass + compositor to be less heavy on render times.

Thanks!

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