Assign a Paint Effects brush to Hair

You can assign a Paint Effects brush to the nHair system. This is useful for creating effects, such as vines or feathers for hair. The hair output can be Paint Effects or NURBS curves.

To assign a Paint Effects brush to hair

1. Select a brush from the Content Browser.
2. In the Outliner, select the hairSystem.
3. Select nHair > Assign Paint Effects Brush to Hair.
4. The brush now replaces the hair. Depending on the brush, you may need to tweak the settings in the brush’s Attribute Editor. Try doing the following:
   • Change the Global Scale.
   • Go to the Tubes section, then Creation and adjust the look and size of tube segments.
   • Go to the Tubes section, then go to Behavior and then Forces and set Path Follow to 1 and Length Flex to 1. You can also increase the Path Attract value, which makes the brush stroke cling to the curve.
   • For more information, see Tips for Paint Effects brushes assigned to Hair.
5. If you originally output to Paint Effects, then in the pfxHairShape node you may want increase Display Quality.
6. In the hairSystemShape you may want to reduce the Hairs Per Clump to 1 and adjust the Clump Width Scale.
   Tip: To create your own hair look with polygons, you can create a mesh brush and paint a test stroke, then assign this brush to the hair system following the procedure above. Next, convert the Paint Effects to polygons. You can even texture these with hair images. The width attributes on the hair system still affect the polygons.

   For a better looking polygon, before converting, decrease the brush width (0.05) and set flatness to 1.

   

Tips for Paint Effects brushes assigned to Hair

Overridden Brush Attributes

Hair system hairs become stroke paths for an assigned brush, so each hair is like a brush stroke. The normal of these strokes is determined by the hair's twist vector (as opposed to the surface normal with the regular Paint Effects stroke). The Brush Width attribute on the brush is overridden by the Hair Width attribute on the hair system. The Color1 attribute on the brush is overridden by the hair system color (Hair Color * Hair Color Scale + HSV Rand). Likewise the Specular Color, Specular Power, Translucence, and Multi Streak attributes on the hair system override those on the brush. All other attributes on the hair system, such as Curl and Turbulence, are applied in addition to any similar effects on the brush.

Using Brushes with Tubes turned off

When a brush with Tubes turned off is assigned to a hair system, each hair is like a regular stroke with the width being the Hair Width * Hair Width Scale (the Brush Width on the brush is ignored). This provides a way in which different Brush Types, such as Paint or Mesh can be used to render the hairs. For example you could make the hairs look like ribbons, or strings of pearls.

Generally when doing this you need to set the Hair Width to the desired Brush Width and make the Hair Color attribute the same as the color1 values from the brush. If the brush is textured you will also usually need to increase the u repeat value on the brush (depending on width and length of the hairs).

Using Brushes with Tubes turned on

When assigning a brush with Tubes turned on, you usually want to modify it to better follow the hairs.

Most preset brushes will generate new tubes along the length of each hair. To have the brush instead emit a single tube (or tree) exactly at the base of each hair set the following in the brush’s Attribute Editor:

• Tubes Per Step = 0.0
• Start Tubes = 1
• Tube Rand = 0.0

Then in the hair system’s Attribute Editor, set:

• Hair Width = 0.0 (This makes the Brush Width zero.)

Now to make the tubes better follow the hair curves, set the following in the brush’s Attribute Editor:

• In the Tubes > Behavior section, set all Forces and Turbulence attributes’ values to zero.
• In the Tubes > Width Scale section, set both Elevation Min and Max to zero.
• Adjust Global Scale to best approximate the curve length.
• Increase Path Follow and/or Path Attract to follow the hair.
• IncreaseLength Flexto better follow stretching of the hair.

In doing this the relationship of segments on the brush to CVs on the hairs can affect the results. You may wish to have both values be similar. To adjust segments on the hairs you can either edit the hair system’s Sub Segments or the follicle’s Sample Density (the latter will also affect the dynamic simulation). The segments on the brush can be adjusted through the Segments, Petal and Leaf Segments attributes.