V11.d+ HAIR and Collision Detection

[John Bigboote]

I've been toying with v11's hair and collision-detection and came-up with a test scenario you may find helpful should you wish to experiment with this feature. In my opinion, it works, but could do with some improvement.

 

Here's a movie...project will follow in subsequent post:

CollDetect_test.mov

[John Bigboote]

And here's the project. Feel free to dink with the settings and show us the optimal settings.

 

One thing I learned: The denser the mesh, the better CD will work. At first I had the bottom surface of the blue 'brush' as only 1 surface with the hair mat applied to it and I got NO response from the collision detection. So I made the little divisions (more patches) and that helped CD a lot.

 

Still, there's definately some 'weirdness' happening with the CD...

 

I look forward to seeing what others can do.

 

Think: 'carwash'...

HAIR_collision_detect_test.prj

[msfolly]

Hey there.

 

I have attached two avi clips.

- One has hair dynamics on, but collisions off.

- The other one has collisions on, and if you look closely, the hair is going THROUGH her ear. Weird.

 

You vid is interesting, and collisions are working fine for you.

What do you think my problem is?

[John Bigboote]

I didn't see any movie clips attached...I think you can only attach 1 (1mb limit) per reply. I'll have a looksee tho...

[msfolly]

Oooops!

Zipped them together.

two_avi_files.zip

[NancyGormezano]

As a curiosity John (Matt...which do you prefer?) - haven't played with the files - but does it appear that the collision detection is better with the cube or pyramid than the sphere? Its obvious from the movie that the cd is not quite right with the sphere - but can't really tell with the other objects.

[msfolly]

You are right, Nancy. Better on the other two shapes.

 

Maybe I should give her pointy ears?

[John Keates]

The thing to remember about hair collision is that the thing that collides is the guide hairs - not each individual hair. This improves calculation times and makes the movement compatable with poses etc but means that you might run into limitations.

 

It is possible to use poses for specific movements so it should be possible to work around problems with a clear idea of what you want and suitible planning.

[msfolly]

I'll have to try that. Thanks.

[cfree68f]

Melissa,

 

the problem could also be if you are using a skullcap and I think you are. If so.. you need to have the cap outside of her skull and bring it into place with an action or pose.. so that the hair does not start out colliding. That "MAY" help.

 

Johns right about the collision being on the guides.. so you might make the skullcap around the ears denser to see if you get more guides to work with (cumbersome at best) or comb the hair back and over the ear.

 

Make sure your stiffness settings in the dynamics are stiff enough to keep the hair combed back. Also play with the constraint type. "Spring" might work better with collision than constraint (not sure).

 

Hope that helps.

 

C

[msfolly]

Actually, although it is a skull cap, it is OUTSIDE THE SKULL. I used Conform to keep it on top of the skull. The patches are pretty dense already around the ear, I will post a spline map.

[John Bigboote]

So it looks like to get Collision detection working better the solution (might be) to use a really, really, dense scalp and because that is denser you can thereby lower the density on your hair emitter. Lowering the hair emitter's density will lower the amount of secondary filler follicles that are created, and because these 'filler' strands are whats crashing thru the geometry you would almost want to eliminate them altoghter. This would make grooming the hair slower, but with much more control as well.

 

I'll give this a try tomorrow on my 'carwash' test project.

 

Ms. Folly, nice test...is that you? Did you see my hair test? Click on my weblink and select the 'hair' button on my webpage. I hope you don't easily offend...

[cfree68f]

Melissa. I think I have a solution for you. What you need is a direction map. The advantage of this is that it "aims" the hair from the base.. instead of bending it as combing does.

 

Try this...

 

http://www.colins-loft.net/hairbrush.html

 

its an app I wrote to help paint hair direction maps. They are tricky because they use the different colors of the RGB channels to paint the direction. Red one way Blue another and Green 256 tweeks between increments. The paint app makes it a little easier to paint them as it paints the appropriate color in the direction you want the hair to go. Its good for parts and general hair styling. The problem is, this overrides Hashs combing once the map is applied.. so its all one way or the other.

 

Theres a tutorial as well that might help. I think if you get the hair going in the right direction.. the collision will be fine.

 

You are right in that the skull Cap is more than dense enough.

 

Try combing the hair over the ears back first (without collision on) Then turn on collision and see what happens. If combing doesn't work.. try hair maps.

 

Hope that helps.

 

C

[msfolly]

Okay, after I get her rigged, (which may be some time) I will try all the different approaches above and report back!

 

- John, GREAT web site. I am going to have to click on those little links under people's names more often! Loved the hair test! Also loved the moving, well, whatever. I need to use that effect on the earrings and the um, whatevers, on my model too! Your Stones video rocks!

 

- Colin, "aiming it from the base" sounds interesting. I will try it. (with fear and trepidation - I THOUGHT I was finished with the hair. I find it hard to manage.)

 

The hair on that cap is actually divided into 4 groups. Bangs, Top of head, In front of ear, and the back. There are actually 4 different hair materials, which allows me to control the material for each area separately. There is another patch over where the part is on the top of the head. That is what that extra thingy on top is. I had to separate out different hair lengths, sorta like a hairdresser does, and style it in sections. The hair that is going through the ear is not tucked behind it, the patchs that do that are not causing me any problems. That area has SHORT material that is pretty thick.

 

Also, I had not gotten around to deleting the skull patches under the skull cap, so maybe the other areas are more protected? Perhaps I should try working on some sort of geometry for the back of the ear. Instead of making the ear sprout out of the head like a real ear, I will give it a sharp angle. The hair would hide it, I think, and the difference between the sphere and the square and pyramid on John's test is striking!

 

Maybe I will just tweak the area that has problems, or just turn off collisions for that part only. Avoidance may be easer than a real fix. I KNEW trying to realistically style it was going to be a problem.

 

For the record, msfolly stands for Melissa's mistake. Email names don't like apostrophes! Ah well, Ms. Folly is ALSO apt.

 

"She could easily pass for 65 in the dark with the light behind her." Yeah, me, sorta; without the extra pounds from xmas and wrinkles from a well spent life. When I started, I did not know much about image maps. A un-intended virtual make over!

 

M

[cfree68f]

The hair on that cap is actually divided into 4 groups. Bangs, Top of head, In front of ear, and the back. There are actually 4 different hair materials, which allows me to control the material for each area separately. There is another patch over where the part is on the top of the head. That is what that extra thingy on top is. I had to separate out different hair lengths, sorta like a hairdresser does, and style it in sections. The hair that is going through the ear is not tucked behind it, the patchs that do that are not causing me any problems. That area has SHORT material that is pretty thick.

 

Ingenious! why didnt I think of that? See? you are allready teaching no tricks to old dogs.

 

Keep it up.

 

C

[msfolly]

Miracles happen every day...