SWIFT++ can be compared to various other packages in terms of functionality provided. Packages that we consider are those that are publicly available. A word about the spectrum of polyhedral proximity query algorithms is in order. On one end is a set of algorithms that take advantage of convex models to speed up proximity queries. These algorithms give a lot of useful proximity information but are restricted to convex models. At the other end of the spectrum are algorithms that can deal with arbitrary collections of triangles. These algorithms can deal with any type of polyhedral collection but are more restricted in the queries that they can answer. SWIFT++ can deal with general polyhedral models while giving substantial proximity query information.

Convex packages rely on objects being convex or composed of convex pieces. There are two main classes of algorithms that are used for convex polyhedral proximity query. One is the Voronoi region based Lin-Canny (LC) algorithm and its derivatives. Another one is the simplex-based Gilbert-Johnson-Keerthi (GJK) algorithm and its derivatives. V-Clip, an LC improvement and modification, was shown to be faster than the enhanced GJK algorithm. SWIFT is shown to be faster than V-Clip. Until the advent of V-Clip, GJK was the most robust. Now, SWIFT and V-Clip are more robust. Taking advantage of multiresolution representations in conjunction with LC, the H-Walk system, developed at Stanford, uses V-Clip as a subroutine along with an inner Dobkin-Kirkpatrick hierarchy (DKH) to "walk" more quickly to the minimum of the distance function. The SWIFT system uses an outer hierarchy of simpler bounding volumes to accelerate the walking. Below is a brief description of each publicly available convex package. More can be learned about them at their respective sites.

• SWIFT is an improved LC implementation
  • Provides sweep and prune bounding box support
  • Employs outer bounding hierarchies to speedup walking
  • Performance can be made independent of motion coherence
  • Allows objects composed of convex pieces
  • Allows only for rigid motion
  • Very robust

• V-Clip is an improved LC implementation
  • Does not provide sweep and prune bounding box support
  • Allows objects composed of convex pieces
  • Allows only for rigid motion
  • Very robust
  • Requires QHULL only if using convex decompositions

• I-Collide is the original LC implementation
  • Provides sweep and prune bounding box support
  • Allows only for rigid motion
  • Not very robust

• SOLID is a GJK implementation
  • Computes penetration depth
  • Allows deformations which keep objects convex
  • Requires QHULL

Polygon soup packages operate on lists of triangles. They typically create a hierarchy of bounding volumes whose leaf nodes are the triangles themselves. The hierarchies are composed of spheres, AABB's (Axis-Aligned Bounding Boxes), OBB's (Oriented Bounding Boxes), SSV's (Sphere-Swept Volumes), or k-DOP's (k-Discrete Oriented Polytopes). These packages are designed to handle rigid motion but some may be adapted to work based upon deformable objects. More can be learned about them at their respective sites.

• SWIFT++
  • Uses convex hull bounding volumes
  • Computes intersection detection, tolerance verification, exact and approximate minimum distance computation, and disjoint contact determination
  • Heavily exploits coherence
  • Provides sweep and prune bounding box support
  • External preprocessing of models required

• RAPID
  • Uses OBB bounding volumes
  • Computes intersection detection

• PQP
  • Uses SSV bounding volumes
  • Computes intersection detection, tolerance verification, and exact and approximate minimum distance computation
  • Takes some advantage of coherence

• QuickCD
  • Uses k-DOP bounding volumes
  • Computes intersection detection
  • Takes some advantage of coherence

• V-Collide
  • Uses RAPID
  • Provides sweep and prune bounding box support
  • Computes intersection detection