Houdini 20.5

Hair and fur

How to create, style, and add dynamics to hair and fur.

The tools the Hair Utils shelf let you quickly set up hair and fur objects, jump between objects, as well as animate and simulate. The tools on the Guide Process tab are used to style the fur, as they let you influence the placement and orientation of guide hairs by painting skin attributes.

Tip

The hair and fur tools often process large VEX arrays. If you observe memory issues, consider setting the HOUDINI_VEX_MEMORYCACHESIZE environment variable to 1.

To create fur, start with a piece of geometry and use the Add Fur tool on the Hair Utils shelf. By default, two nodes are created: Guide Groom and Hair Generate.

The Guide Groom and Hair Generate networks have the exact same set up with the exact same workflow, except the hair generation network has less outputs. This makes it very simple to use, since everything is done in SOPs with curves. The Guide Process node lets you layer many different operations, and very easily control where the operation takes place along the curve using ramps or by painting attributes on the skin. This allows you to easily create natural looking hair and fur very quickly.

One improvement is that there is no longer a separation between manipulating guide curve geometry or painting skin attributes. Everything flows through a single graph. All of the components that make up the groom are displayed in a single network. Each of the nodes also have at least 3 inputs and 3 outputs, which allows the 3 types of data to flow through the nodes. This results in a very clean and easy to read network, and eliminates the need to reference other nodes. Another advantage is that the operators can be placed in any order, which gives you complete control and flexibility.

Note

Mantra uses the SOP network you create to do the grooming and does the cooking of the node network (SOP network) at render time. It does this without taking a license, which allows for rendering with Engine for hair, fur, and anything else that’s comprised of curves and points (grass).

Note

Grooming should always be done on the static mesh, not the animated mesh.

Subtopics

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

Houdini 20.5

Getting started

Using Houdini

  • Geometry

    How Houdini represents geometry and how to create and edit it.

  • Copying and instancing

    How to use copies (real geometry) and instances (loaded or created at render time).

  • Animation

    How to create and keyframe animation in Houdini.

  • Digital assets

    Digital assets let you create reusable nodes and tools from existing networks.

  • Import and export

    How to get scene, object, and other data in and out of Houdini.

  • MPlay viewer

    Using Houdini’s stand-alone image viewer.

Character FX

  • Character

    How to rig and animate characters in Houdini.

  • Crowd simulations

    How to create and simulate crowds of characters in Houdini.

  • Muscles and tissue

    How to create and simulate muscles, tissue, and skin in Houdini.

  • Hair and fur

    How to create, style, and add dynamics to hair and fur.

  • Feathers

    How to create highly realistic and detailed feathers for your characters.

Dynamics

  • Dynamics

    How to use Houdini’s dynamics networks to create simulations.

  • Vellum

    Vellum uses a Position Based Dynamics approach to cloth, hair, grains, fluids, and softbody objects.

  • Pyro

    How to simulate smoke, fire, and explosions.

  • Fluids

    How to set up fluid and ocean simulations.

  • Oceans and water surfaces

    How to set up ocean and water surface simulations.

  • MPM

    How to simulate different types of solid materials (such as snow, soil, mud, concrete, metal, jello, rubber, water, honey, and sand).

  • Destruction

    How to break different types of materials.

  • Grains

    How to simulate grainy materials (such as sand).

  • Particles

    How to create particle simulations.

  • Finite elements

    How to create and simulate deformable objects

Pipeline

  • Executing tasks with PDG/TOPs

    How to define dependencies and schedule tasks using TOP networks.

  • HQueue

    HQueue is Houdini’s free distributed job scheduling system.

  • Houdini Engine

    Documents the Houdini Engine C, Python APIs, and Houdini Engine plugins

  • Machine Learning

    Houdini provides a platform for machine learning which supports synthetic data generation, preprocessing, training models, exporting trained models, and deploying trained models

Nodes

  • OBJ - Object nodes

    Object nodes represent objects in the scene, such as character parts, geometry objects, lights, cameras, and so on.

  • SOP - Geometry nodes

    Geometry nodes live inside Geo objects and generate geometry.

  • DOP - Dynamics nodes

    Dynamics nodes set up the conditions and rules for dynamics simulations.

  • VOP - Shader nodes

    VOP nodes let you define a program (such as a shader) by connecting nodes together. Houdini then compiles the node network into executable VEX code.

  • LOP - USD nodes

    LOP nodes generate USD describing characters, props, lighting, and rendering.

  • ROP - Render nodes

    Render nodes either render the scene or set up render dependency networks.

  • CHOP - Channel nodes

    Channel nodes create, filter, and manipulate channel data.

  • COP - Copernicus nodes

    COP nodes provide real-time image manipulation within a 3D space.

  • TOP - Task nodes

    TOP nodes define a workflow where data is fed into the network, turned into work items and manipulated by different nodes. Many nodes represent external processes that can be run on the local machine or a server farm.

  • APEX - APEX nodes

    APEX nodes provide operations for building up the functionality of APEX graphs, which are used in KineFX to create character rigs and perform other geometry manipulation.

Scene building, Karma rendering, Image processing

  • Solaris and Karma

    Solaris is the umbrella name for Houdini’s scene building, look development, and Karma rendering tools based on the Universal Scene Description (USD) framework.

  • Copernicus

    Houdini’s 2D and 3D GPU image processing framework.

  • Compositing

    Houdini’s compositing networks let you create and manipulate images such as renders.

Mantra rendering and shading

Reference

  • Menus

    Explains each of the items in the main menus.

  • Viewers

    Viewer pane types.

  • Panes

    Documents the options in various panes.

  • Windows

    Documents the options in various user interface windows.

  • Stand-alone utilities

    Houdini includes a large number of useful command-line utility programs.

  • APIs

    Lists all the reference documentation for the ways you can program Houdini.

  • Python scripting

    How to script Houdini using Python and the Houdini Object Model.

  • Expression functions

    Expression functions let you compute the value of parameters.

  • HScript commands

    HScript is Houdini’s legacy scripting language.

  • VEX

    VEX is a high-performance expression language used in many places in Houdini, such as writing shaders.

  • Properties

    Properties let you set up flexible and powerful hierarchies of rendering, shading, lighting, and camera parameters.

  • Galleries

    Pre-made materials included with Houdini.

  • Houdini packages

    How to write and combine multiple environment variable definition files for different plug-ins, tools, and add-ons.

  • hwebserver

    Functions and classes for running a web server inside a graphical or non-graphical Houdini session.