Houdini 19.5 Hair and fur

Generating hair cards for games

There are two tools on the Hair Utils shelf that you can use to generate hair cards and apply textures for realtime applications. The Generate Hair Cards tool converts hair or fur into polygon cards, while keeping the style and shape of the groom. These polygon cards require far less memory and less computational power to render and display than dense hair curve. It uses a Hair Card Generate node to assigns groups of nearby curves to clusters and then generates polygon cards for each cluster, with the width and orientation matching the original curves.

Note

You can use this tool without having any initial hair generated. You can simply groom the guides and create hair cards directly from the guides.

Once you generate the hair cards, you can use the Hair Card Texture tool to generate the textures. This tool is typically used after the Generate Hair Cards tool to create textures for the generated hair cards. It creates the materials, a render node, and some default hair strips to use as a starting point.

Each of the four strip regions contains a few hundred strips, and each one is matched to the region that most closely matches the length and width proportions of the hair card. For example, the shorter hairs on the top use the strip on the left, and the longer strips near the bottom use the strip on the right so that there is minimal stretching of the texture.

Tips

To...Do this

Change the look and shape of the hair strips

Dive inside the Hair Generate node and use the parameters on the hairclump and guideprocess nodes to tweak the frizz, waviness etc.

See the rendered hair with textures

  1. Dive inside the ropnet and select Bake Hair Card Textures.

  2. Press the Render button to generate textures.

  3. Navigate back to the object level to see the hair cards with the textures applied.

Change the color of the hair

  1. Dive inside the materials and select the Hair Shader VOP.

  2. On the Primary Reflection tab, change the Root Color and Tip Color. The Hair Shader will automatically transition the color between the root and the tip.

Note

To see changes in the viewport, you must click the Render button again on the Bake Hair Card Textures node to regenerate the textures. You must also and select Render > Update Textures in the viewport to refresh the scene.

Hair and fur

Working with fur

Shelf tools for creating fur

  • Add Fur

    Adds fur to a surface.

  • Create Guides

    Creates a guide curves from a skin geometry or manipulates the guides of another groom object.

  • Groom

    Creates a Guide Groom SOP ready to draw & brush curves.

Shelf tools for styling with guide processes

  • Initialize Guides

    Gives the guides an initial direction.

  • Curve Advect

    Advects curves using a vector field generated from curves drawn on the skin surface.

  • Groom

    Creates a Guide Groom SOP ready to draw & brush curves.

  • Reguide

    Interpolates guides between planted guides.

  • Set Guide Direction

    Points guides in the direction of a vector.

  • Set Guide Length

    Lengthens or shortens guide hairs.

  • Lift Guides

    Lifts curves off the skin or flattens them against it.

  • Straighten Guides

    Straightens the hair by bending each segment back so that it’s in the same direction as the previous segment.

  • Smooth Guides

    Blends the shapes of the neighboring guides to create a smoother look.

  • Frizz Guides

    Offsets the curve points along the guide hairs to create a frizzy look.

  • Bend Guides

    Bends curves in a certain direction and by a certain angle.

  • Clump Guides

    Creates bunches of guide hairs.

  • Part Guides

    Lets you draw a parting line on the skin geometry.

  • Add White Hairs

    Adds the required attribute to mark hairs as white hairs in the standard hair shader.

Shelf tools for animating and simulating fur

How to