no fun with shag hair - need help

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  02 February 2002
no fun with shag hair - need help

I'm having a problem with shag hair/fur. I'm doing a model of a horse and working on the mane. The problem is that when I calculate the dynamics, my hair goes through my model.

I have tried playing with every spinner and have poored through the manual several times. I have the fur standing up at the begining of the simulation and then the gravity takes it down to position but even though I have collision set on my model the strands still go through the model. THIS IS DRIVING ME BATS!

Has anyone ran into this problem and knows the magic formula that I can't figure out.

  02 February 2002
Right, couple of things to check on this one...

First of all - you have set your horse mesh as a Collision object? - on rereading you thread I see that you have, but always good to double check

If so then have you tried flipping the nomals of the mesh?

For a simple test - put a "Normal" modifier at the top of the horses stack and check "Unify Normals" - if there are still problems, flip them. (If in doubt, uncheck any 'Force 2-sided'/'2-sided mats'...etc and see if the model is inverted.)

And if there are problems still....

How many segments/knots do you have set for your hair? Shag by default ignores segments in collisions, but there is a check box for enabling them.

If none of the above work, then there is a (sort) of alternative. If anything it will see if the problem persists...

Download Simcloth (free) from Shag's creators Chaos Group at:

Now, you can select your ShagView object and check the box marked "turn to cloth mesh" - and apply Simcloth to calculate the dynamics for you (again, using the horse as a deflector). If in doubt, check out the sample Shag Hair scene file that comes with the SimCloth examples. The downside is that Simcloths dynamics are much like the (now removed) complex dynamics that came with ShagFur/Hair as standard... so it's a lengthy process and it's much harder to retain the hairs original shape in a simualtion. But as I said, it should be a good test to see if the dynamics are still messing up in your scene.

If all fails - then the classic "sphere with fur" tests could be a good start, see if the dynamics still make the hair fall through the object. and if so, get on the phone to Digimation .

Of course, if you (and we) are lucky, the Matt Clarke will write a Shag Hair/Fur tutorial for us all... :P (especially how to achieve the bright "rim light" effect evident in his Chewie renderings/Showreel) *cough* please *cough* hint *cough*

Anyway, hope some of this gibberish helps!
  02 February 2002
Thanks AJ,

When I used the simcloth version, It did the trick. I did a little test with the shag dynamics by taking a sphere and having it colide with a clump of hair. Every time (even with 50 knot segs) it went through the collision object.

The simcloth version on the same test worked perfectly. Only prob now is the calc time (SO SLOW!!!!). I guess I will have to deal with the speed issue. At least now it works.

Thanks again for your help.


p.s. I found that if I have a stong backlight, use the hair shader with a hot tight spec, and turn on shade middle and vert strands in the shag roll-out that I can get the same backlight effect Matt got on the Chewie model. Give it a try. I'll post a file later when I come up for air.

Make sure your lights are shadow casting with at least a 512 shad map.
  02 February 2002
OK here is an update. Looks good so far but have to use the sim-cloth engine.

He is a link to a small movie test.

Thanks again for all of your help man.

  01 January 2006
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