Friday, July 13, 2012

3D Spline Modeling and Patch Modeling, Introduction

The majority of 3D model creation software packages available, from expensive industry leaders such as 3D Studio Max and Maya, to the popular shareware software Milkshape, utilize polygon meshes as the basis for model making. In what has become a standard in both the game and movie making industry, in polygon modeling, 3d models are created by building a mesh from square-shaped planes consisting of two or more flat triangles.

However, 3D polygon modeling is not an efficient technology for creating 3D human characters. By their very nature, polygons are multi-faceted, whereas the organic form is curved. Thus, making an organic model using polygons results in a very dense high polygon mesh, which generates the illusion of soft life-like curves. Unfortunately, high polygon models render slowly, particularly in realtime, making them undesirable if not unusable for game character modeling.

3D Spline Modeling

Spline modeling, also known as patch modeling, is an efficient alternative to using polygons for organic modeling. A spline in 3D modeling is a line that describes a curve. The curve is defined by a number of points. The curved spline can then be lathed or extruded to create 3D geometry. A mesh created from intersecting splines consists of areas called patches.

Patch Modeling

Patches within a spline mesh may resemble polygons in form, but patches have a major advantage in organic modeling. A single patch can define a curved surface that would require a dense collection of polygons to achieve a similar effect, with the additional benefit of not being multi-faceted on close inspection.

Spline Animation

The economy of form resulting from a 3D model created from splines becomes particularly evident when animating. The smooth single-faceted surface of patches within a spline mesh are not subject to the deformation which organic models created with polygons are notorious for. This makes rigging a spline-based model easier than its polygon-based counterpart, which will require complex and time-consuming weighting of the joints to counteract unwanted deformation.
A famous example of spline organic modeling and spline animation is Victor Navone's Alien Song. Created entirely in splines, Navone credits the Alien Song video as the reason Pixar employed him. He has since worked on such features as Finding Nemo, The Incredibles, and Wall-E, which won an Oscar for Best Animation.

Spline Modeling Software

Due to the predominance of 3D polygon modeling as the preferred standard in 3D modeling software, there are very few packages devoted exclusively to natively using spline and patch modeling. Those that do exist include JPatch, and Animation Master. Animation Master by Hash, Inc. leads the field in spline modeling with a proprietary spline-based technology that has been constantly improved and refined since the first appearance of Animation Master, known then as Animation Apprentice, in 1987.
Spline modeling is available in traditional polygon modelers such as Maya, 3D Studio Max, SoftImage, Blender and LightWave 3D in the form of Nurbs modeling, or through additional plug-ins or scripts.

Spline Modeling Technique Summary

  • A spline is a single line drawn in 3D space which describes a curve.
  • The curvature of the drawn spline is divided by points.
  • Splines that intersect through points define planes of three or more sides called patches.
  • A 3D grid composed of patches formed by intersecting splines is known as a spline mesh.
  • A spline mesh can be modified within 3D space by adding additional points to the mesh and connecting these points with splines to create new patches, or by altering the position of existing splines at the point of intersection, which alters the curvature of the patch surface.
  • The curves of a spline mesh are truly curved, making spline and patch modeling ideal for creating organic life-like models.

Spline Modeling For Organic Modeling

While polygon modeling has its place, for creating realistic 3D character models for games, animations or movies, spline modeling can offer far superior results, both in terms of efficiency in the speed of the modeling workflow, and the economy of the resulting 3D mesh.
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