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Modeling and Texturing 3D-Hair

by Marco Barnig

Introduction

In the last years, a lot of innovations have been done to improve modeling and texturing of 3D-hair. Creating and animating hair that appears realistic still presents a real challenge to 3D-artists. The following techniques have evolved over the past years:

  • Volume hair
  • Clip map hair
  • Geometry hair
  • Environmental hair
  • Particle hair

Volume hair

Volume hair is the oldest and most common 3D-hair technology. It is created with simple geometry that forms the volume of the hair. The hair often looks plastic and plain. Another problem is that it is difficult to animate this type of hair.

Volume hair is the typical Poser hair (figure 1). Some very innovative artists have developped different technologies to improve the plastic shell look of the volume hair:

  • use of advanced geometry to create realistic meshes for various hair styles. A skilled artist in this field is Greg Crowfoot of the GreyLight collectif.
  • use of bump maps to simulate strands (figure 2)
  • use of transparency maps to simulate fine lines and depht. The Poser master for this technique is Kozaburo (figure 3)
  • use of morph targets to simulate movement. The leader in creating morphs for Poser figures is E. VanDycke (Traveler).
    • Old woman with typical volume hair Volume hair with bump map Volume hair with transparency maps
    figure 1
    figure 2
    figure 3

    Clip map hair
    A clip map is a black and white image (transparency map) that's used to clip portion of a 3D-model. This technique is used since ten years. Paul Hafeli presented in 1999 in the Poserforum a method to paste the texture map of scanned hair on a flat surface of a one sided square attached to the head of a poser figure. I improved this technique by merging the square with a face mask to allow overlapping of the hair with the face.
    Square & Facemask
    Hair-Texture-Map
    Transparency map
    Result
    Click on the gallery to view my Poser model "Sara Proft" with different hair styles exported from the Cosmopolitan My Style CD.

    Geometry Hair
    New utilities in 3D programs made it possible to build a single strand of hair and to replicate it over the surface of the mesh. At the beginning the hair was sticking stright out from the skin. The technique evolved and special effects such as random jitter, contour, curl and kink provides realisme. The results are usually very high polygon counts that are difficult to manage on a medium range computer. FiberFactory2, Furrific and scatter are three common plugins for 3D programs to generate geometry hair.

    Environmental Hair
    3D Model Marylin Monroe; c Virgin Lands Computeranimation
    The environmental plugin's Shag:Fur and Shag:Hair from Digimation for the program 3D Studio Max are used to add fur or hair to an objects's surface and to control the density, color, thickness, direction, leaning, bending, shadow and highlight of the hair. All parameters are animatable to produce subtle motion, growing or color change. As no real geometry is created, it is quick to render.

    Particle Hair
    The best solution for creating realistic and animated hair is the use of particle systems, but it is not yet attainable for mid-range 3D programs. Particle based hair-systems were used in several Hoolywood films like Jumanji and American Werwolf in Paris. Most systems are custom developed for specific films. One system called Compuhair is commercially available, some others are in development.

    Stuart Little: the state of art in digital hair modeling and animation
    Stuart Little; c Sony Pictures Imageworks Stuart Little is the digital computer generated star of a live-action movie released by Columbia Pictures/Sony Pictures Entertainment Film on december 10, 1999.

    The fur on Stuart's body consists of more than 450.000 computer rendered hairs. The research & development team of Sony Pictures Imageworks, the creator of Stuart Little, developed in-house tools in the 3D modelling & animation software Maya (from Alias-Wavefront) using a combination of MEL (Maya Embedded Language), RenderMan DSOs (dynamically shared objects), macros and plug-in's to customize the commercial software package. Final hair was drawn with RiCurves primitives, a series of micropolygons along a curve in a ribbon-like shape that has its widest part facing at the camera.

    Stuart Little represents today's (year 2000) state of art of digital hair modeling and animation .

    Bibliography

    1. Bill Fleming: How to be Furrific ! Animation World Magazine, Issue 3.2, May 1998
    2. Barbara Robertson: Building a better mouse; Computer Graphics World, Volume 22, Issue 12, December 1999
    created 1/7/2000
    © 2001 Marco Barnig
    last update: 29/07/2001