Create hair and fur clumps

You can create hair and fur clumps maps using the Clumping modifier. Clumping modifiers lets you generate regions on the surface that pull spline tips together to form clumps. This effect reproduces the natural clumping effect of real hair. You can also use it to gather splines for grass clumps in landscape scenes.

When creating a clumping map, you specify:

• The location of the clumps and clump guides using a points map.
• The areas that each clump guide affects using a Ptex map, region map, or another clumping map.
• Clumping attributes using slider controls, Ptex maps, or expressions.

  Use these methods to set the strength of the clump, noise, and more.

Create the points map

1. Add a Clumping modifier to your Description. See Shape and control primitives using XGen modifiers.
2. In the bottom section of the Clumping Modifier attributes, click Setup Maps.

   The Generate Clumping Maps window appears.

3. In the Points section of the Generate Clumping Maps window, specify how to generate the point map for the clumping guides (see Create point maps for XGen modifiers).

   After creating the point map that specifies the location of the clumping guides, you specify how to you want to map the clumping regions around the guides. You do this in the Maps section of the Generate Clumping Map window.

4. If you want to save the clumping map to a location other than the default directory, click the icon and specify a new location.

Specify the control map settings

After creating the point map that specifies the location of the clumping guides, you specify how to you want to map the clumping regions around the guides.

XGen automatically sets up Control Maps if the Description is using a Region Map and its Region Mask is set to a value greater than 0 (meaning that the Region Map is being used). This ensures that the clump maps you create respect the region boundaries defined by the Region Map.

Any subsequent Clumping modifier added to the Description uses the previous Clumping module's maps as control maps to maintain boundaries between regions and clumps. If you create a Region Map for the Description after setting up a Clumping modifier, you need to rebuild all clumping maps, starting with the first one in the Modifiers list, so that the new region boundaries are used by the clumping maps.

You setup the Control Maps in the Maps section of the Generate Clumping Map window (see Generate Maps window).

1. If you want to save the clumping map to a location other than the default directory, click the icon beside Map Dir and specify a new location.
2. Set the Radius Variance.

   This randomizes the radius of the clumps.

3. If the Description is using a Region Map or the map you are creating is the second clumping map in a modifier chain, Use Control Maps is on by default.

   This ensures that the clumping guides respect the boundaries defined by the Region Map of the current Description.

4. (Optional) Set a value for a Control Mask.
5. If you want to use a Region Map (or another clumping map) from a location other than the default directory, click the icon beside Control Map and browse the location.
6. If Control Map is off, set the Texels Per Unit.

   Sets the texel resolution of the Ptex clumping map.

7. Click Save to generate the clumping map.
8. In the Modifiers tab, set the Clumping attributes to produce the desired effect.

   See Clumping modifier options.

9. Preview the Description.
   Note: You can add more primitive control CVs to increase the deformation effect of a modifier. To do this click the Primitives tab and in the Primitive Attributes section, increase the Modifier CV Count value.

Create additional clumping modifiers

To further refine your hair or fur, you can add a second Clumping modifier to your groom. A second Clumping modifier generates its clumps inside the areas defined by the first Clumping modifier, creating a combined clumping effect.

When you create a second modifier, note the following:

• Use a higher density points map.

  For example if you set the Points Density of the first Clumping modifier to 5, set the Points Density of the second Clumping modifier to 10 or higher and use the prior clump modifiers' maps as a control. This ensures that the new clump regions and guides reside within the prior clump's regions. If this option is not used, the primitives may instead be influenced by clump guides in more distant regions, creating undesired results.

• Use Control Maps is automatically turned on and Control Map is set to use the first Clumping modifier as a map.

Related tasks

• Animate spline primitives using an Anim Wires modifier
• Shading and Rendering XGen Primitives