I just downloaded the release candidate for blender 2.74 because it said on the release notes that it has "Support for hair collision with meshes" and I would like to make it so that my hair particles stay inside of a hood that I modeled for my character. If anyone could give me insight on how exactly I can accomplish this effect it would be greatly appreciated.
You can't just turn on collision on the object and expect it to work.
Here is how u do it: first of all create your hair particle system.
Next turn on Hair Dynamics and turn on collision on the object. Now go to the mesh with collision on and turn up the "soft body and cloth" outer and inner paramaters to say around 5 for both.
Now you can go back to the hair and turn up the steps to about 40 in the Dynamics tab. Now you should have good collision without the other nonsense. Also be careful when changing the other paramaters, it can slow everthing down tremendously.
Yeah this is a really good question. Out of the four main physics units I've tried, them being Clothify, Soft Body, Particle Emission and Hair, the hair seems to be the type with the least consistency.
In the broadest terms, you would think the problem posed above would produce no problem, what with the way the system has handled during numerous tests over the past few days. Even in Particle Edit mode, moving a hair strand across a solid plane or face will cause the hair to refuse to pass through; instead it will stick to the surface. Whether there is an issue with the physics engine that has yet to be addressed or something we're both missing, I don't know.
As for the best solution to your issue, the only thing I can come up with would be to duplicate the objects for the moment, add a "collision" physics to both the body and clothing objects and then let the simulation run for a frame or two. Then, with the particle system selected, go into particle edit mode and start dragging, preening, cutting and replacing hairs in the system in keeping with the desired outcome. It would probably be best if any "quality" values in the particle system are kept as high as your system can handle and the number of segments likewise.
In addition to this, under the "Hair Dynamics", try adjusting the mass down as well as the stiffness and damping up to reduce too much movement on the ends. If all else fails, go into weight paint mode on the mesh's particle system and start increasing the weight on the more annoying and wayward hair strands.
Hope this helps.