Combing

Most fur isn't simple random fuzz with no direction; real fur follows the natural shape of the animal's body! Even grass and moss have a preferred direction to their fibers.

Sasquatch gives you a variety of tools to comb fibers. While there are only a few controls, they are extremely powerful.

Simple Bias Combing

The easiest combing method is a simple directional bias which pushes the fibers in one direction. In figure below you can see an object with with no combing and with bias combing. In this example, the bias comb pushes every fiber strongly to the right. This kind of combing is simple, but very common for many situations.

The strength of this bias is controlled by the Combing Bias control. In the figure, it's set at 100%, but you often use smaller values to push the fibers less strongly.

By default, bias combing will push your fibers down, in the -Y direction. If you want to choose a different direction, you can use the Comb Bias Controllers item picker to choose an object. (Null objects work well for this.) The combing bias direction will then be defined by the -Y direction of the object at frame 0.

Simple Bias Combing

S Panel Strength

You can use the S~panel to control the Combing Bias strength over the surface of your object. This is extremely useful to have precise control over the combing. It's not uncommon to use an image map to force stronger combing in a place where the fur is too "puffy," or to remove combing in areas where it causes intersections with the object geometry. Another use is to ruffle the fur with fractal noise.

Multiple Bias Combing

A single directional bias is useful for simple and common situations, but is too limited for advanced styling. If you want the combing direction to vary over your object's surface, you can use multiple bias controls to direct the direction of the fur at every point on your object. Sasquatch interpolates the direction between the guides.

You can see this effect in figure below. Two bias controllers were added, one pointing down and to the right and one pointing down and to the left. The fibers near each controller are combed in that controller's direction. Fibers inbetween the controllers are interpolated smoothly.

Multiple Bias Combing

You can scale the controllers to make them more powerful compared to each other. The overall combing strength is still set by the Combing Bias, but you can make one controller have a larger range of influence by making it bigger than its neighbors. If all of the controllers are the same size, they are all equally important.

You can use multiple bias combing to manually style any surface. A simple surface might use one or two controllers, but you can use more as necessary to manually define any combing pattern you like. Of course this becomes tedious when you have a complex surface. It would be possible to comb an animal this way, but there's a better solution: Smart Combing.

Automatic "Smart" Combing

Quick Tip
Quick Tip
Here's a short video showing how to use Sasquatch's Smart Combing feature.
We've found that manual combing is powerful, but tedious. Setting up dozens of directions manually isn't that hard, but it still takes several minutes to configure. To solve this annoyance, you can use Smart Combing. This powerful feature makes the computer do the combing by analyzing your object's geometry and deriving the natural object contours automatically. You can see the effect of this in figure below.

No combing and Smart Combing from the animal's nose surface

Smart Combing is very simple to use since Sasquatch does the work for you. The computer only needs one clue from you to decide how to start the combing; it needs to know where to start. For a wolf, the computer doesn't realize that fur shouldn't be brushed from the tail to the head, or up one leg and down another. But if you give it a starting clue, the computer can use that to smoothly derive the combing over the rest of your object.

For example, if the combing of a real wolf starts from the head and moves down the neck, it's obvious and natural for us to see that the combing must continue down the back and tail (not up from the tip of the tail) and down the legs (not up!). Of course this isn't obvious and natural to the computer, but Sasquatch's Smart Combing teaches it.

This initial direction is provided by a surface on your object. The combing crosses from this named surface and heads towards the other surface(s) in your object. For a wolf, you might imagine the "starting surface" to be the wolf's nose. Fur, starting at the nose, is brushed towards the rest of the face. Face hair is brushed to the neck, neck hair to the body, and so on down the legs. Thus, by naming the nose, you defined the entire combing for the whole animal!

The combing surface doesn't have to have fur on it; that's not important for defining the comb direction. You just need to pick a starting surface (or surfaces) for the combing to start at. These named surfaces will be combed too, so it's reasonable to pick the entire head of a wolf to be the combing surface, even though the head and body are both being furred. All the surface selection does is define the initial direction of the combing.

To activate Smart Combing, enter the source surface(s) in the Comb Definition Surface(s) control. You can use the `*' wildcard, and enter multiple surfaces separated by commas, just as described on page~\pageref{surfaceselector}.

Surface Comb Strength sets the strength of Smart Combing. Like Combing Bias, you can use the S~panel to texture map it. You can also use both combing methods simultaneously. Often the Smart Combing does most of the work, but you use an S~panel to "touch up" problem areas with manual bias controller combing.

Effector Combing

Quick Tip
Smart combing
Here's a short video showing how to use Sasquatch Effector Combing.

This lets you use one or more effectors to stroke the fur combing in a limited region without affecting the combing anywhere else. This can help to fix up small areas, like angling tufts of fibers out of eyes or tuning the flow of fur around a mouth. It uses effectors much like Acid. The effectors can be moved, rotated, and stretched to define the combed region. The combing is in the effector's -Y direction. You can use as many effectors as you like. There's two independent channels of effector combs so you can texture map the strength of groups independently.You can also change the strength of indivdual effectors by using that effector's Polygon Size. Effector combing is added to the previous "smart" combing and bias controllers. Probably you'll set up most combing using the older methods, and add limited region effectors just to fix up the small areas that have remaining problems.

Maximum Sleekness

Combing is essential, but strong combing can create the problem of the fibers being pushed so hard that they become parallel to the surface. If your surface itself curves at all, this may make the fibers dip under the surface and disappear! The { Maximum Sleekness control prevents combed fibers from becoming too strongly combed. If you lower this value, the fur will be prevented from being combed beyond a certain limit. This guarantees that the fur has some volume to it. Sometimes it's useful to control fur by using strong combing, but using an S~panel image map on Maximum Sleekness to force it to "puff out" from the surface in the areas you paint.

Setup Pose Frame

In very rare cases, it's useful to have a specific kind of extra texturing and combing control of advanced character setups. Sasquatch applies combing or texturing based on null objects in the scene. If your object is very dynamic, such a running cheetah, it can be difficult to see where the nulls are relative to the undeformed, "basic" shape of your model. Since Sasquatch by default analyzes the shape and pose from frame 0, you may already be ``using'' this frame to set up your dynamic action. However, using the Setup Pose Frame option, you can set this ``pose'' frame to be anything you like. Typically, you choose a large negative frame like -100. Then, you can pose your character at that time in a way that makes it easy to view the texturing/combing pose, and you have lots of "time" to get your character back into its action pose by the start of your real scene at frame 0. This is a very advanced option that will only apply to the most ambitious Sasquatch users, so it's OK to ignore this option forever; you'll know when you hit the situations when it's useful and necessary.

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