Hair with gravity

[joepal]

I've played around a bit with hair that actually hangs down in animations, independent on which angle the head is held in. These are some quick and dirty results.

Approximate time to model hair (after MHX import to blender) : ten minutes
Approximate time to render: an hour



Crappy youtube version: http://www.youtube.com/watch?v=zkNxcI7iMTk
DVD-resolution render (xvid) : http://www.jwp.se/files/hairdemo.avi

Ok, she should fire her hairdresser, the eyes look kind of spooky with that gaze thing, and hair grows straight through her ears, but it demonstrates the point.

[Marbury Intermedia]

That's nice work. Could you try to add more hair segments? It may slow down your render time but should give you a more realistic results. My poor system comes to a crawl when I even think about rendering hair.

[Rhynedahll]

This is modled hair and not particle hair, yes?

[joepal]

This is blender-internal particle hair only. As far as I know, that's the only way to implement functional gravity, but I might be wrong.

[Rhynedahll]

Are you using 2.49 or 2.55?

Seems like you must be using 2.49 as in 2.55 the particle hair dynamics doesn't work, as far as I know.

[joepal]

No, I'm using 2.55 official beta. The particle hair works but bugs a bit. Some strands get locked even though no manual editing (ie "comb" or "cut" etc) has been done.

[Rhynedahll]

I'm talking specifically about the Hair Dynamics. With this checked, the hair does not collide with the emitter mesh (the model) but passes right through it.

Unless you figured out how to make this work?

[ThomasL]

You probably need to enable the mesh as a collision object. However, collision detection takes TIME, so you need an invisible lowpoly object for collision.

There is also the problem that the hair might fall into the skull. This can be fixed by weight-painting the strands; the root should be red and the tip blue.

[joepal]

I did none of the above for this particular video. I just tweaked the various forces (emitter tangents, gravity...) so that the hair would look like a common haystack.

I'll redo the hair demo eventually, I've figured out a better scheme for making reasonable haircuts (without combing/cutting) by defining a few extra vertex groups.

[Rhynedahll]

You probably need to enable the mesh as a collision object.

This I know.

However, collision detection takes TIME, so you need an invisible lowpoly object for collision.

I just tested the lowpoly idea with an iconosphere and a cube. When using the Hair Dynamics, the hair particles do not collide with anything.

There is also the problem that the hair might fall into the skull. This can be fixed by weight-painting the strands; the root should be red and the tip blue.

When using a vertex group (for example an area of the head designated as Scalp) to control density of the emitted hair particles, and Hair Dynamics, Blender 2.55 automatically weight paints the vertex group and the strands.

I also tested this with an iconosphere.

1) I weight painted the entire object to 1 (red) to see if it made any difference. The hair particles did not collide with the mesh at all but simply fall straight through.

2) Weight painting the hair particles to (a) all red and (b) red at root and all blue make no difference. The hair particles do not collide with anything.

The Hair Dynamics tab, when checked, makes the hair behave like real hair, except for the problem of no collision. I've posted on the Blender Artists forum about this and others have also encountered the problem, but no one has yet figured out how to fix it.
The general supposition is that the feature has not yet been completed, i.e. no collision check.