Houdini 20.0 Nodes Geometry nodes

Hair Generate 2.0 geometry node

Generates hair on a surface or from points.

Since 17.0

Optionally uses curves as guides for shaping the generated hair.

Note

This node can generate stable output from just animated skin and guides, as long as both have a rest attribute. This can be used as an alternative to plugging in rest skin and guides to the first and second inputs and animated skin and guides into the third and forth inputs.

Parameters

General

Distribution

Mode

Scatter On Surface

Scatter guides on the surface skin surface.

Per Point

Generate a guide at each point of the skin geometry.

Group

Generate curves for this group of skin primitives.

Density

Scatter hair or guides at this density.

This parameter can be overridden using an attribute or texture. To do this, select an option from the drop-down menu next to the parameter.

Scatter Seed

The seed value used for scattering. Changing this generates a different random distribution with the same density.

Relax Iterations

The number of times to relax guide locations after scattering. Higher iterations result in a more even distribution of guides at the cost of more computation time.

Relax Using Normal Attribute

Takes the surface normal attribute into account when scattering.

Optimization

Prune

Prune a percentage of hair to speed up cooking.

Pruning Ratio

The percentage of curves to prune.

Limit To Bounding Box

Only grow hair from root points that are within the bounding boxes defined by the parameters below.

Box Size

The size of the bounding box.

Center

The center of the bounding box.

Guide Weights

This node generates hair using by blending the shape of nearby curves. These parameters control how much each guide influences the shape of generated hair.

Use Guides

Blend between the shape of nearby guide curves to determine the shape of the each generated hair.

Assume Uniform Segment Count & Length

Use a faster guide interpolation algorithm, which requires that all guides have the same segment count.

Compute Weights Using Skin Coordinates

Compute guide weights using the hair’s position within its skin primitive. This is robust and accurate, but can look less natural than weight computation based on guide distance, which is used when this is disabled.

This can only be used when guides are located at each skin point.

Tip

Use the Guide Groom Object's Guide Per Point mode to create guides that work with this method.

Blending Method

Controls how guides that influence a generated curve are blended.

Linear Blend

Does a straight-forward linear blend between the guide curves.

Extrude And Blend

Extrudes the curve along each guide and then blends those extruded curves.

Guide Group

The group of guides to use.

Influence Radius

The radius within which guides have influence over generated hair.

This parameter can be overridden using an attribute or texture. To do this, select an option from the drop-down menu next to the parameter.

Influence Decay

Controls how steeply the weight of a guide drops with distance. Higher values cause guides to have less influence over distant hairs, resulting in hair more closely following guides near them. Lower values tend to result in a smoother look as the effect of all guides is averaged.

This parameter can be overridden using an attribute or texture. To do this, select an option from the drop-down menu next to the parameter.

Maximum Guide Count

The maximum number of guides to take into account. Any excess guides found within the Influence Radius are ignored.

This parameter can be overridden using an attribute or texture. To do this, select an option from the drop-down menu next to the parameter.

Max Guide Angle

Ignore guides that face away from the skin normal at the hair root by more than this angle in degrees.

This parameter can be overridden using an attribute or texture. To do this, select an option from the drop-down menu next to the parameter.

Clump Crossover

Blends the shapes of clumps of guide hair. At a value of 0, only the clump that exhibits the greatest influence of the generated hair is taken into account. Higher values cause surrounding clumps to be taken into account as well.

TIP: Guide hair clumps can be created using the Hair Clump SOP.

This parameter can be overridden using an attribute or texture. To do this, select an option from the drop-down menu next to the parameter.

Create Guide & Weight Attribs

Outputs the guide indices and weights used for interpolation as array attributes on the generated primitives.

Unguided Hairs

Grow Unguided Hair

Grows hair at points that are outside of the influence radius of any guides.

Use Initial Direction Attribute

Grow hair in the direction of a vector attribute on the skin geometry.

Initial Dir Attrib

The name of a vector attribute on the skin geometry used as the initial direction of unguided hair.

Segments

Generate hairs with this segment count.

Note

When there are any guides, this node generates hairs with the same segment count as those guides and this parameter is ignored.

Length

Generate unguided hair of this length.

This parameter can be overridden using an attribute or texture. To do this, select an option from the drop-down menu next to the parameter.

Minimum Length

The minimum length required to grow a hair. Any hair that would be shorter than this value is not grown at all.

Attributes & Appearance

Thickness

Create Thickness Attribute

Add a thickness attribute to generated hair.

Thickness Attribute

The name of the created thickness attribute.

Thickness

The thickness of generated hair at it’s thickest point.

Hair Profile

The profile of thickness along the length of each hair.

Source Attribute Transfer

These parameters control how skin attributes are transferred from the skin to generated hair.

Point Attributes

A list of attributes to transfer from the skin geometry’s points to the hair primitives.

Uses the interpolated value at the skin location closest to each hair root.

Vertex Attributes

A list of attributes to transfer from the skin geometry’s vertices to the hair primitives.

Uses the interpolated value at the skin location closest to each hair root.

Primitive Attributes

A list of attributes to transfer from the skin geometry’s primitives to the hair primitives.

Uses the values of the primitive closest to the hair’s root location.

Detail Attributes

A list of attributes to transfer from the skin geometry’s detail to the hair primitives.

Guide Attribute Transfer

Point Attributes

A list of attributes to transfer from the guide points to the generate hair points.

Primitive Attributes

A list of attribute to transfer from the guide primitives to the generated hair primitives.

See also

Geometry nodes