Dynamic Hair Tutorial Part 3 (Collisions and hair settings)

Welcome to the third part of the dynamic hair tutorial, by me, if you have not checked out part one or two of the tutorial, check it out here: PART 1, PART 2.

In part 1, we have gone through setting up the mesh needed (skinned to joints) for a dynamic hair simulation, and also went through the setting up of curves for the dynamic hair system.

In part 2, we have gone through the connections, connecting the curves and joints and the mesh.

In this part 3, we will be going through setting up the collisions of the hair curves and some of the more important settings (that I felt was) of the hair system.

Please make sure you have your part done file that you used for the previous tutorial.

To start off, load up your file (if you have closed it) and check that you have the following items from the previous tutorial:

 In the GEO_GRP:
Mesh (model/object)

In the Rig_GRP:
Joint chain (skinned to mesh)
Hair follicles (in the master joint)

inputCurves (child of their respective hair follicles)

 In its own hairSystem_GRP:
Output hair curves (not the same as the original curves)
Hair systems

 For this lesson, all you need are the curves (either inputCurves or your outputCurves, pick one), and go to: Hair>Create Constraint>Collide Sphere

Do take note creating collide spheres/cubes (whichever suits your needs) you can only select a curve at a time and have a collide sphere/cube for a curve. However. you can have more than 1 constraint to a curve.

What it does is that it creates a sphere that collides with the hair NURBS Curve that was simulated. When created it will be at the center of the curve that you have selected on default. You can scale and reposition the collide sphere to anywhere you want the curve to collide into.

Rescaling of collide sphere.

A better perspective of the collide sphere following the curvature of the curve.

One useful way is to place it at the end (or if you want a very silky and flowy hair that bends a lot, you can have it go along the curvature of the curve) to prevent the hair from penetrating into the head.

So do all the collide spheres for all the curves and...

You should get something like this.

You can also create multiple collision spheres/cubes for one curve, like I did above.

Parent the constraints under the master joint (or any control in the rig that controls the master joint) because you want the collide spheres to move with the head and not stay there when the head moves.

I made a controller and a head joint (supposedly I followed how I would have rigged a full character [but then again the mesh is pass the origin on the negative side {for tutorial purposes only}]. I have provided a full expansion view of my outliner, just for you to check and if you have any questions, you may comment or send me a mail.

Your final result, without messing around with the hairSystem would be something like this:

As you can see, the hair is pretty crazy, we would not want them to fling about when the character is being animated (please take note that, I did not create this in scale, also I do not think that correct scale is required).

I will be talking about the hairSystem settings and attributes (the ones which are of more importance).

Dynamics tab in the hairSystem

(I will not talk about the clump and hair shape tab)

#1 Iterations
Iterations controls the repetitions per time step of the hair solver, the higher the value, the more the hairSystem will calculate on the stiffness and the length flex, increasing accuracy and the cost of the simulation.

#2 Length Flex
Basically how much the hair curve can stretch along its length.

#3 Stiffness
Well, as the name suggests, it controls whether the hair curve is flexible or not.

#3.5 Stiffness Scale
Left to right: root of hair to tip of hair (start of hair curve to end of hair curve)
Down to up: not stiff to stiff

#4 Forces tab

I will not elaborate a lot here, since the most important one that I feel is the mass. The other settings, you can go to the help section of Maya itself and search "hairSystemShape" without the open inverted commas.

#4.5 Mass
Mass defines the mass (amount of matter in the hair), or if you want (although not scientifically equal), the weight of the hair.

That kind of sums up what I use overall. There are some attributes that you want to explore, those are fine even if it is in its default values.

Collisions and Turbulence is worth checking out.

After changing the settings on both the hairSystem, this is the final result that I have got:

I might be doing an extra tutorial continuing this one (like an extra part) talking about FK-ing this hair after being simulated to allow more control over the hair for animators.

You can get my working file here:

Please be reminded that this file is for learning purposes and is not to be abused in any matter, if you want to share or improve on it, just a credit will do, thanks.

If you have any questions, you can leave a comment or you can send an e-mail to me. Thank you for your audience.