Adaptive Subsurf makes Hair disappear #50091

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Tom Telos · 2016-11-22T19:04:16+01:00

Tom Telos commented

2016-11-22 19:04:16 +01:00

Here is a cube with some simple hair. AdaptiveSubsurfDisappearsHair.blend
The hair renders fine (Cycles) unless I press adaptive on the Subsurf modifier.

Thank you, gurus, for your attention.
I was trying to apply displacement on a hair material,
in a way that increases toward the tip, by using the hair strand intercept,
aiming for a look similar to that of Drosera trichomes .
The math seems to be working fine, as evidenced by the emission strength,
but the exact same strength value applied to Displacement has no effect,
even when I specify Experimental and True displacement.

So I tried to invoke microdisplacements by checking Adaptive on a Subsurf modifier,
and, to my surprise, hair ceases to render.

Thank you again, and congratulations on a magnificent project!

Here is a cube with some simple hair. [AdaptiveSubsurfDisappearsHair.blend](https://archive.blender.org/developer/F405051/AdaptiveSubsurfDisappearsHair.blend) The hair renders fine (Cycles) unless I press adaptive on the Subsurf modifier. Thank you, gurus, for your attention. I was trying to apply displacement on a hair material, in a way that increases toward the tip, by using the hair strand intercept, aiming for a look similar to that of [Drosera trichomes ](https://upload.wikimedia.org/wikipedia/commons/thumb/0/06/Drosera_rotundifolia_leaf1.jpg/1280px-Drosera_rotundifolia_leaf1.jpg). The math seems to be working fine, as evidenced by the emission strength, but the exact same strength value applied to Displacement has no effect, even when I specify Experimental and True displacement. So I tried to invoke microdisplacements by checking Adaptive on a Subsurf modifier, and, to my surprise, hair ceases to render. Thank you again, and congratulations on a magnificent project!

Tom Telos commented

2016-11-22 19:04:17 +01:00

Changed status to: 'Open'

Tom Telos commented

2016-11-22 19:04:17 +01:00

Added subscriber: @ttelos

Mai Lavelle commented

2016-11-22 23:36:14 +01:00

Added subscriber: @MaiLavelle

Mai Lavelle commented

2016-11-22 23:36:14 +01:00

Changed status from 'Open' to: 'Archived'

Mai Lavelle closed this issue

2016-11-22 23:36:14 +01:00

Mai Lavelle self-assigned this 2016-11-22 23:36:14 +01:00

Mai Lavelle commented

2016-11-22 23:36:14 +01:00

So there's two things to mention here:

First is that displacing hair geometry itself isn't supported, and probably won't be. Hair is represented as curve primitives which aren't really surfaces the way a polygon mesh is, so they can't be displaced as you want.

The other thing is hair on meshes with adaptive subdivision is currently disabled. There's a bit of an issue with how hair syncing was implemented that make it a bit tricky to have both at the same time, but eventually this will work. Hair still wont be displaced tho.

For the effect you're trying to achieve, the best thing to do is actually model the objects rather than use hair. You'll have much more control over the result that way.

So there's two things to mention here: First is that displacing hair geometry itself isn't supported, and probably won't be. Hair is represented as curve primitives which aren't really surfaces the way a polygon mesh is, so they can't be displaced as you want. The other thing is hair on meshes with adaptive subdivision is currently disabled. There's a bit of an issue with how hair syncing was implemented that make it a bit tricky to have both at the same time, but eventually this will work. Hair still wont be displaced tho. For the effect you're trying to achieve, the best thing to do is actually model the objects rather than use hair. You'll have much more control over the result that way.

Tom Telos commented

2016-11-22 23:51:36 +01:00

THANK you:
if the problem is not going to be solved,
it is very time-saving to know that!

THANK you: if the problem is not going to be solved, it is very time-saving to know that!

Reuben Tilahun commented

2021-12-07 17:18:10 +01:00

Added subscriber: @Reuben-4

Reuben Tilahun commented

2021-12-07 17:18:11 +01:00

@Mai Lavelle What? A very common example. Adaptive subdivision for terrain displacement, then grass scattered on it. Please don't tell me to use the displacement modifier as it is not the same as the displacement node and I did all the procedure of ramping the grayscale value from 0-1 and baking it to get a perfect displacement map and there is a difference between the modifer and node, not only that but Geo Nodes doesn't work with adaptive subdiv. poly count skyrockets when using standard subdivision to handle dense grounds for VFX. I can't even use a texture to affect the scattering since blender will ignore shader displacement when scattering any object so they don't follow the contour of the terrain.

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Adaptive Subsurf makes Hair disappear #50091