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Blender 3.3. I'm fiddling with the new hair stuff and have sculpted some fur for my model. However, I'm having trouble getting the "volume" (in the hair sense, not the CAD sense) right. Specifically, all my hairs have a sort of exponential-curve shape relative to the surface; that is, they start almost perpendicular to the surface and then point more outward at the tips.

Real hair/fur of course does the exact opposite; it's perpendicular to the skin on emergence and then lies flat(tish) against the body.

I really don't want to start over; I have direction, clumping, and tip-to-skin distances that are satisfactory. Is there any way to adjust only the roots of my hairs so that they are more perpendicular to the surface, while leaving the rest of the hair mostly unaffected?

For bonus points, is there any way to make hairs repel each other without also being repelled from the surface? (Basically, to reduce self-intersection without otherwise affecting the shape more than necessary?)

Puffing doesn't help; it's actually what produced this effect in the first place. Combing doesn't help either as it presses the hair too close to the surface. What I need seems to be a comb mode in which the hairs also repel each other and the underlying surface?

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  • $\begingroup$ Check out Blender 3.5 if you can. It comes with a lot of improvements for hair such as pre-made Geometry Node assets to control the hair, better edit mode (still under development), new nodes for interpolating hair children, quick fur, and there is even a demo blend file with 4 different fur examples: blender.org/download/demo-files/#hair $\endgroup$
    – Blunder
    Commented May 15, 2023 at 11:37
  • $\begingroup$ @Blunder, thanks for the marketing spiel</s>. Does it address this specific problem any better than 3.3? (Ability to select roots would be an improvement; can 3.5 do that?) $\endgroup$
    – Matthew
    Commented May 15, 2023 at 16:51
  • $\begingroup$ Unfortunately, selecting the roots is still not possible in Blender 3.5. But if you can make the selection grow as you wrote in your answer you should be able to select them when you invert the selection. -- Another approach is to use Geometry Nodes. You can rotate the hair at the roots if it's too close to the surface. $\endgroup$
    – Blunder
    Commented May 22, 2023 at 1:14

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I found a method that sort-of works, although it's somewhat reliant on combing properly in the first place, plus lots of careful smoothing. It's also somewhat dependent on hairs being of equal length.

The key is enabling 'Use sculpt selection', which is an unassuming and easily overlooked icon next to the mode drop-down (i.e. 'Sculpt Mode'). Until I stumbled on that, I couldn't figure out why selection wasn't doing anything.

The "right" way to do this is to start with hairs completely normal to the surface. Newly added hairs that aren't interpolating shape will be like this. Existing hairs can be restored to this state with gratuitous use of the 'Puff' brush.

At this point, the trick is comb without affecting the roots. To achieve this, turn on 'Use sculpt selection' and choose 'Endpoints' from the 'Select' menu'. You should notice the hairs dimming. Now choose 'Grow' from the select menu a few times, watching as the tips of the hairs lighten to indicate that they are selected; stop before the entire hair is selected. Now, combing will only affect the selected part of the hairs.

This will of course result in some nasty kinks where the selected and unselected parts of the hairs meet. Gentle grooming starting with more hair selected and gradually reducing the selection might help, but judicious use of the 'Smooth' brush should also be able to set things right.

A similar trick can be used to try to repair hairs that have been overly flattened, although once the bulk of the hair is too close to the surface, it's quite hard to repair without starting over. That said, if a sort of 's' curve is acceptable, selecting most of the hairs as above, then choosing 'Invert' from the 'Select' menu, will allow using the 'Puff' brush on just the roots. Again, this can be done incrementally and/or cleaned up with 'Smooth'.

(It's most unfortunate that there is no ability to directly select roots.)

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