mental matter® is an extremely versatile and powerful modeling library comprised of modular components which support Hierarchical Subdivision Surface (HSDS) and Free-Form Surface (FFS) modeling techniques. Several different types of free-form surfaces, such as Non-Uniform Rational B-Spline (NURBS) surfaces, are supported. The HSDS representation allows for arbitrarily complex geometrical objects, traditionally assembled from many individual small patches that are carefully stitched or blended together, to be represented easily by a single subdivision surface. In addition, the HSDS representation supports high interactivity rates for 3D animation and other applications.
An optional module complementing mental matter provides the revolutionary Shape-By-Shading™ (SBS) modeling technology. It allows artists to create 3D geometry in HSDS representation interactively by shading with an electronic pen on a computer tablet or Tablet PC in place of using traditional pencil and paper. SBS can be integrated as a plug-in into any DCC or CAD application that contains mental matter.
In addition to offering modeling capabilities, mental matter also supports conversions between surface types, for example bidirectional conversion between NURBS surfaces and hierarchical subdivision surfaces, so that multiple modeling techniques can be used on the same surface. For example, surfaces can be imported from traditional NURBS modeling tools to perform modeling operations on the HSDS representation and the result exported back to the NURBS modeler or to a machining device. Other capabilities, such as mesh simplification, are also provided to prepare input data for modeling.
Hierarchical Subdivision Surface Modeling
The HSDS library supports hierarchical subdivision surfaces made of triangles or quadrilaterals. It includes tools for the construction, manipulation and tessellation of hierarchical subdivision surfaces, as well as full multi-resolution editing for modeling or animation of the surface at different levels of detail. Edits can be propagated to coarser and finer levels by analysis and synthesis, respectively, and an extended version of synthesis allows for interactive performance in the vertex move cycle. The HSDS library provides modeling operations on edges, vertices, faces and arbitrary points on the surface, including support for smooth creases, vertex features, direction manipulation of the surface at arbitrary points, trimming, and topology editing on the base mesh. Supported surface attributes include texturing with an unlimited number of texture spaces and arbitrary dimension per texture space, materials, and displacement mapping.
Free-Form Surface Modeling
The FFS library has two-tiered support. Its base is the Geometry Approximation library, which provides support for polygon meshes and for free-form curves and surfaces. The Geometry Approximation library provides adaptive tessellation techniques which the user can control, as well as texturing, materials, and displacement mapping. The functionality of the Geometry Approximation library can be extended through the use of shaders. The FFS library includes a set of NURBS surface modeling shaders which can be used to create several different kinds of NURBS surfaces, including standard primitives, ruled surfaces, u- and uv-loft surfaces, lathed surfaces, and extruded surfaces.
Modeling with Shape-By-Shading
The SBS library is a content authoring tool which bridges the gap between the creation of 3D computer models and 2D representations of them. Artists can shade using an electronic pen on a computer tablet or Tablet PC, just as they would use a pencil on paper, to express shape design ideas by shading. The SBS shaping algorithm first interprets the shading as a 2D picture of a 3D object with given lighting conditions, and then creates that 3D object. Both triangular and quadrilateral hierarchical subdivision surfaces can be shaped, and the HSDS library provides the necessary subdivision surface support. SBS uses local refinement to provide adequate detail, vertex editing to create the desired shape, and analysis and synthesis to propagate the edits to all levels of the resulting mesh hierarchy. The SBS library provides access to shaping algorithm parameters, and supports creation of an OpenGL® shade view.
Surface Conversions
Surface conversions allow multiple modeling techniques to be used on one surface. mental matter supports polygon mesh and NURBS surfaces to HSDS conversion, as well as HSDS to NURBS surfaces conversion. The polygon mesh to HSDS converter takes any arbitrary genus, 2-manifold mesh, with or without boundaries, as input. It re-samples and re-meshes the input to a quad dominate mesh, and reduces the density of the mesh. Features on the input mesh are preserved. The user has control over sampling density and depth of the resulting surface. The NURBS surfaces to HSDS converter can handle multiple trimmed NURBS surfaces as input, with optional specification of topology information. It can automatically detect adjacent NURBS surfaces. The converter produces one quadrilateral subdivision surface with the minimum number of base faces required to meet accuracy requirements given by the user. The HSDS to NURBS surfaces converter adaptively produces a minimum set of NURBS surfaces based on detail vectors of the subdivision surface. It supports creases and vertex features, and accounts for trimmed faces. Topology information for the resulting NURBS surfaces is provided.
Polygon Mesh Simplification
The Polygon Mesh Simplification library allows the user to work more efficiently with large data sets. It reduces surface complexity while maintaining surface quality and prepares meshes for import into the HSDS library. It supports triangular meshes as input, and reduces the number of primitives as much as possible while preserving surface topology and quality. The user has control over the target percentage of primitives to be decimated.
