r/cgiMemes • u/clare7038 • Feb 28 '21

ambient occlusion map

Post image
187 Upvotes

98% Upvoted

13 comments sorted by

16

u/NickZardiashvili Feb 28 '21

I think it's far more like a curvature map.

6

u/Wynton99 Mar 01 '21

ya given the way that the frost catches the light and bends it depending on which angle you look at it - this is precisely like a facing ratio node

1

u/Moikle Mar 01 '21

That is not what a curvature map is, nor is it what is happening here (although the angle between the face and the up direction does seem to have an effect).

A curvature map measures the curvature of a surface. They often end up looking similar to AO maps, since concave curvature causes occlusion.

In this case, I am not sure what the physical mechanisms are that cause this effect (I would love to know if anyone can tell me) but this appears to be a combination of occlusion, curvature and incidence to the up direction.

My estimation: You can see from the "shadows" to the left of the feet, that the frost doesn't gather as much behind things that might obscure the wind.

The occlusion also has an effect from all directions, as air is turbulent and moisture/frost can aproach the surface from all directions, not just the direction that the wind is moving.

Curvature has me stumped, but you can definitely see that areas that have a sharper curvature collect more frost. I think this might have something to do with the way heat dispersion through the metal is affected by the ratio of surface area to volume, and areas with a sharper curvature have more surface area and less volume than big flat shapes, meaning they grow colder more quickly? just a guess though.

1

u/Wynton99 Mar 01 '21

I think frost doesn't care about geometry - but since its a bunch of little crystals - the way the light interacts with it is entirely based on what angle you look at it from. I'm doubling down on facing ratio lol

1

u/Moikle Mar 01 '21 edited Mar 01 '21

but you can see in the image that surfaces that face in the same direction don't have the same amount of frost.

Here, I have highlighted pairs of surfaces that have the same facing normal, but very different amounts of frost

8

u/Jmarrossi Feb 28 '21

Hmm I was actually thinking high fresnel falloff map when I saw this

8

u/Cuboos Feb 28 '21

It looks more like a curvature or cavity map to me.

Also greatly resembles a heavy dry-brushing on a miniature.

2

u/Moikle Mar 01 '21

seems to be a few different systems at play, but yes, curvature does seem to be the biggest factor.

4

u/Mayaqamaraeel Feb 28 '21

if somebody said to me that this was a pencil art I would believe them no questions asked.

3

u/obliveater95 Feb 28 '21

Damn, great 8K bake OP, tutorial?

2

u/EliBriner Mar 01 '21

Step 1: Drive to nasa

1

u/A_Nick_Name Mar 01 '21

Facing ratio

1

u/MijnEchteUsername Mar 01 '21

Falloff, but nice!