from the start... checking in ode-0.9

1 files changed, 790 insertions, 0 deletions

diff --git a/libraries/ode-0.9/ode/src/collision_space.cpp b/libraries/ode-0.9/ode/src/collision_space.cpp
new file mode 100644
index 0000000..1a8fc81
--- /dev/null
+++ b/libraries/ode-0.9/ode/src/collision_space.cpp
@@ -0,0 +1,790 @@
+/*************************************************************************
+ *                                                                       *
+ * Open Dynamics Engine, Copyright (C) 2001-2003 Russell L. Smith.       *
+ * All rights reserved.  Email: russ@q12.org   Web: www.q12.org          *
+ *                                                                       *
+ * This library is free software; you can redistribute it and/or         *
+ * modify it under the terms of EITHER:                                  *
+ *   (1) The GNU Lesser General Public License as published by the Free  *
+ *       Software Foundation; either version 2.1 of the License, or (at  *
+ *       your option) any later version. The text of the GNU Lesser      *
+ *       General Public License is included with this library in the     *
+ *       file LICENSE.TXT.                                               *
+ *   (2) The BSD-style license that is included with this library in     *
+ *       the file LICENSE-BSD.TXT.                                       *
+ *                                                                       *
+ * This library is distributed in the hope that it will be useful,       *
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of        *
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the files    *
+ * LICENSE.TXT and LICENSE-BSD.TXT for more details.                     *
+ *                                                                       *
+ *************************************************************************/
+
+/*
+
+spaces
+
+*/
+
+#include <ode/common.h>
+#include <ode/matrix.h>
+#include <ode/collision_space.h>
+#include <ode/collision.h>
+#include "collision_kernel.h"
+
+#include "collision_space_internal.h"
+
+#ifdef _MSC_VER
+#pragma warning(disable:4291)  // for VC++, no complaints about "no matching operator delete found"
+#endif
+
+//****************************************************************************
+// make the geom dirty by setting the GEOM_DIRTY and GEOM_BAD_AABB flags
+// and moving it to the front of the space's list. all the parents of a
+// dirty geom also become dirty.
+
+void dGeomMoved (dxGeom *geom)
+{
+  dAASSERT (geom);
+  
+  // if geom is offset, mark it as needing a calculate
+  if (geom->offset_posr) {
+    geom->gflags |= GEOM_POSR_BAD;
+  }
+  
+  // from the bottom of the space heirarchy up, process all clean geoms
+  // turning them into dirty geoms.
+  dxSpace *parent = geom->parent_space;
+
+  while (parent && (geom->gflags & GEOM_DIRTY)==0) {
+    CHECK_NOT_LOCKED (parent);
+    geom->gflags |= GEOM_DIRTY | GEOM_AABB_BAD;
+    parent->dirty (geom);
+    geom = parent;
+    parent = parent->parent_space;
+  }
+
+  // all the remaining dirty geoms must have their AABB_BAD flags set, to
+  // ensure that their AABBs get recomputed
+  while (geom) {
+    geom->gflags |= GEOM_DIRTY | GEOM_AABB_BAD;
+    CHECK_NOT_LOCKED (geom->parent_space);
+    geom = geom->parent_space;
+  }
+}
+
+#define GEOM_ENABLED(g) ((g)->gflags & GEOM_ENABLED)
+
+//****************************************************************************
+// dxSpace
+
+dxSpace::dxSpace (dSpaceID _space) : dxGeom (_space,0)
+{
+  count = 0;
+  first = 0;
+  cleanup = 1;
+  current_index = 0;
+  current_geom = 0;
+  lock_count = 0;
+}
+
+
+dxSpace::~dxSpace()
+{
+  CHECK_NOT_LOCKED (this);
+  if (cleanup) {
+    // note that destroying each geom will call remove()
+    dxGeom *g,*n;
+    for (g = first; g; g=n) {
+      n = g->next;
+      dGeomDestroy (g);
+    }
+  }
+  else {
+    dxGeom *g,*n;
+    for (g = first; g; g=n) {
+      n = g->next;
+      remove (g);
+    }
+  }
+}
+
+
+void dxSpace::computeAABB()
+{
+  if (first) {
+    int i;
+    dReal a[6];
+    a[0] = dInfinity;
+    a[1] = -dInfinity;
+    a[2] = dInfinity;
+    a[3] = -dInfinity;
+    a[4] = dInfinity;
+    a[5] = -dInfinity;
+    for (dxGeom *g=first; g; g=g->next) {
+      g->recomputeAABB();
+      for (i=0; i<6; i += 2) if (g->aabb[i] < a[i]) a[i] = g->aabb[i];
+      for (i=1; i<6; i += 2) if (g->aabb[i] > a[i]) a[i] = g->aabb[i];
+    }
+    memcpy(aabb,a,6*sizeof(dReal));
+  }
+  else {
+    dSetZero (aabb,6);
+  }
+}
+
+
+void dxSpace::setCleanup (int mode)
+{
+  cleanup = (mode != 0);
+}
+
+
+int dxSpace::getCleanup()
+{
+  return cleanup;
+}
+
+
+int dxSpace::query (dxGeom *geom)
+{
+  dAASSERT (geom);
+  return (geom->parent_space == this);
+}
+
+
+int dxSpace::getNumGeoms()
+{
+  return count;
+}
+
+
+// the dirty geoms are numbered 0..k, the clean geoms are numbered k+1..count-1
+
+dxGeom *dxSpace::getGeom (int i)
+{
+  dUASSERT (i >= 0 && i < count,"index out of range");
+  if (current_geom && current_index == i-1) {
+    current_geom = current_geom->next;
+    current_index = i;
+    return current_geom;
+  }
+  else {
+    dxGeom *g=first;
+    for (int j=0; j<i; j++) {
+      if (g) g = g->next; else return 0;
+    }
+    current_geom = g;
+    current_index = i;
+    return g;
+  }
+}
+
+
+void dxSpace::add (dxGeom *geom)
+{
+  CHECK_NOT_LOCKED (this);
+  dAASSERT (geom);
+  dUASSERT (geom->parent_space == 0 && geom->next == 0,
+            "geom is already in a space");
+
+  // add
+  geom->parent_space = this;
+  geom->spaceAdd (&first);
+  count++;
+
+  // enumerator has been invalidated
+  current_geom = 0;
+
+  // new geoms are added to the front of the list and are always
+  // considered to be dirty. as a consequence, this space and all its
+  // parents are dirty too.
+  geom->gflags |= GEOM_DIRTY | GEOM_AABB_BAD;
+  dGeomMoved (this);
+}
+
+
+void dxSpace::remove (dxGeom *geom)
+{
+  CHECK_NOT_LOCKED (this);
+  dAASSERT (geom);
+  dUASSERT (geom->parent_space == this,"object is not in this space");
+
+  // remove
+  geom->spaceRemove();
+  count--;
+
+  // safeguard
+  geom->next = 0;
+  geom->tome = 0;
+  geom->parent_space = 0;
+
+  // enumerator has been invalidated
+  current_geom = 0;
+
+  // the bounding box of this space (and that of all the parents) may have
+  // changed as a consequence of the removal.
+  dGeomMoved (this);
+}
+
+
+void dxSpace::dirty (dxGeom *geom)
+{
+  geom->spaceRemove();
+  geom->spaceAdd (&first);
+}
+
+//****************************************************************************
+// simple space - reports all n^2 object intersections
+
+struct dxSimpleSpace : public dxSpace {
+  dxSimpleSpace (dSpaceID _space);
+  void cleanGeoms();
+  void collide (void *data, dNearCallback *callback);
+  void collide2 (void *data, dxGeom *geom, dNearCallback *callback);
+};
+
+
+dxSimpleSpace::dxSimpleSpace (dSpaceID _space) : dxSpace (_space)
+{
+  type = dSimpleSpaceClass;
+}
+
+
+void dxSimpleSpace::cleanGeoms()
+{
+  // compute the AABBs of all dirty geoms, and clear the dirty flags
+  lock_count++;
+  for (dxGeom *g=first; g && (g->gflags & GEOM_DIRTY); g=g->next) {
+    if (IS_SPACE(g)) {
+      ((dxSpace*)g)->cleanGeoms();
+    }
+    g->recomputeAABB();
+    g->gflags &= (~(GEOM_DIRTY|GEOM_AABB_BAD));
+  }
+  lock_count--;
+}
+
+
+void dxSimpleSpace::collide (void *data, dNearCallback *callback)
+{
+  dAASSERT (callback);
+
+  lock_count++;
+  cleanGeoms();
+
+  // intersect all bounding boxes
+  for (dxGeom *g1=first; g1; g1=g1->next) {
+    if (GEOM_ENABLED(g1)){
+      for (dxGeom *g2=g1->next; g2; g2=g2->next) {
+        if (GEOM_ENABLED(g2)){
+          collideAABBs (g1,g2,data,callback);
+        }
+      }
+    }
+  }
+
+  lock_count--;
+}
+
+
+void dxSimpleSpace::collide2 (void *data, dxGeom *geom,
+                              dNearCallback *callback)
+{
+  dAASSERT (geom && callback);
+
+  lock_count++;
+  cleanGeoms();
+  geom->recomputeAABB();
+
+  // intersect bounding boxes
+  for (dxGeom *g=first; g; g=g->next) {
+    if (GEOM_ENABLED(g)){
+      collideAABBs (g,geom,data,callback);
+    }
+  }
+
+  lock_count--;
+}
+
+//****************************************************************************
+// utility stuff for hash table space
+
+// kind of silly, but oh well...
+#ifndef MAXINT
+#define MAXINT ((int)((((unsigned int)(-1)) << 1) >> 1))
+#endif
+
+
+// prime[i] is the largest prime smaller than 2^i
+#define NUM_PRIMES 31
+static long int prime[NUM_PRIMES] = {1L,2L,3L,7L,13L,31L,61L,127L,251L,509L,
+  1021L,2039L,4093L,8191L,16381L,32749L,65521L,131071L,262139L,
+  524287L,1048573L,2097143L,4194301L,8388593L,16777213L,33554393L,
+  67108859L,134217689L,268435399L,536870909L,1073741789L};
+
+
+// an axis aligned bounding box in the hash table
+struct dxAABB {
+  dxAABB *next;         // next in the list of all AABBs
+  int level;            // the level this is stored in (cell size = 2^level)
+  int dbounds[6];       // AABB bounds, discretized to cell size
+  dxGeom *geom;         // corresponding geometry object (AABB stored here)
+  int index;            // index of this AABB, starting from 0
+};
+
+
+// a hash table node that represents an AABB that intersects a particular cell
+// at a particular level
+struct Node {
+  Node *next;           // next node in hash table collision list, 0 if none
+  int x,y,z;            // cell position in space, discretized to cell size
+  dxAABB *aabb;         // axis aligned bounding box that intersects this cell
+};
+
+
+// return the `level' of an AABB. the AABB will be put into cells at this
+// level - the cell size will be 2^level. the level is chosen to be the
+// smallest value such that the AABB occupies no more than 8 cells, regardless
+// of its placement. this means that:
+//      size/2 < q <= size
+// where q is the maximum AABB dimension.
+
+static int findLevel (dReal bounds[6])
+{
+  if (bounds[0] <= -dInfinity || bounds[1] >= dInfinity ||
+      bounds[2] <= -dInfinity || bounds[3] >= dInfinity ||
+      bounds[4] <= -dInfinity || bounds[5] >= dInfinity) {
+    return MAXINT;
+  }
+
+  // compute q
+  dReal q,q2;
+  q = bounds[1] - bounds[0];    // x bounds
+  q2 = bounds[3] - bounds[2];   // y bounds
+  if (q2 > q) q = q2;
+  q2 = bounds[5] - bounds[4];   // z bounds
+  if (q2 > q) q = q2;
+
+  // find level such that 0.5 * 2^level < q <= 2^level
+  int level;
+  frexp (q,&level);     // q = (0.5 .. 1.0) * 2^level (definition of frexp)
+  return level;
+}
+
+
+// find a virtual memory address for a cell at the given level and x,y,z
+// position.
+// @@@ currently this is not very sophisticated, e.g. the scaling
+// factors could be better designed to avoid collisions, and they should
+// probably depend on the hash table physical size.
+
+static unsigned long getVirtualAddress (int level, int x, int y, int z)
+{
+  return level*1000 + x*100 + y*10 + z;
+}
+
+//****************************************************************************
+// hash space
+
+struct dxHashSpace : public dxSpace {
+  int global_minlevel;  // smallest hash table level to put AABBs in
+  int global_maxlevel;  // objects that need a level larger than this will be
+                        // put in a "big objects" list instead of a hash table
+
+  dxHashSpace (dSpaceID _space);
+  void setLevels (int minlevel, int maxlevel);
+  void getLevels (int *minlevel, int *maxlevel);
+  void cleanGeoms();
+  void collide (void *data, dNearCallback *callback);
+  void collide2 (void *data, dxGeom *geom, dNearCallback *callback);
+};
+
+
+dxHashSpace::dxHashSpace (dSpaceID _space) : dxSpace (_space)
+{
+  type = dHashSpaceClass;
+  global_minlevel = -3;
+  global_maxlevel = 10;
+}
+
+
+void dxHashSpace::setLevels (int minlevel, int maxlevel)
+{
+  dAASSERT (minlevel <= maxlevel);
+  global_minlevel = minlevel;
+  global_maxlevel = maxlevel;
+}
+
+
+void dxHashSpace::getLevels (int *minlevel, int *maxlevel)
+{
+  if (minlevel) *minlevel = global_minlevel;
+  if (maxlevel) *maxlevel = global_maxlevel;
+}
+
+
+void dxHashSpace::cleanGeoms()
+{
+  // compute the AABBs of all dirty geoms, and clear the dirty flags
+  lock_count++;
+  for (dxGeom *g=first; g && (g->gflags & GEOM_DIRTY); g=g->next) {
+    if (IS_SPACE(g)) {
+      ((dxSpace*)g)->cleanGeoms();
+    }
+    g->recomputeAABB();
+    g->gflags &= (~(GEOM_DIRTY|GEOM_AABB_BAD));
+  }
+  lock_count--;
+}
+
+
+void dxHashSpace::collide (void *data, dNearCallback *callback)
+{
+  dAASSERT(this && callback);
+  dxGeom *geom;
+  dxAABB *aabb;
+  int i,maxlevel;
+
+  // 0 or 1 geoms can't collide with anything
+  if (count < 2) return;
+
+  lock_count++;
+  cleanGeoms();
+
+  // create a list of auxiliary information for all geom axis aligned bounding
+  // boxes. set the level for all AABBs. put AABBs larger than the space's
+  // global_maxlevel in the big_boxes list, check everything else against
+  // that list at the end. for AABBs that are not too big, record the maximum
+  // level that we need.
+
+  int n = 0;                    // number of AABBs in main list
+  dxAABB *first_aabb = 0;       // list of AABBs in hash table
+  dxAABB *big_boxes = 0;        // list of AABBs too big for hash table
+  maxlevel = global_minlevel - 1;
+  for (geom = first; geom; geom=geom->next) {
+    if (!GEOM_ENABLED(geom)){
+      continue;
+    }
+    dxAABB *aabb = (dxAABB*) ALLOCA (sizeof(dxAABB));
+    aabb->geom = geom;
+    // compute level, but prevent cells from getting too small
+    int level = findLevel (geom->aabb);
+    if (level < global_minlevel) level = global_minlevel;
+    if (level <= global_maxlevel) {
+      // aabb goes in main list
+      aabb->next = first_aabb;
+      first_aabb = aabb;
+      aabb->level = level;
+      if (level > maxlevel) maxlevel = level;
+      // cellsize = 2^level
+      dReal cellsize = (dReal) ldexp (1.0,level);
+      // discretize AABB position to cell size
+      for (i=0; i < 6; i++) aabb->dbounds[i] = (int)
+                              floor (geom->aabb[i]/cellsize);
+      // set AABB index
+      aabb->index = n;
+      n++;
+    }
+    else {
+      // aabb is too big, put it in the big_boxes list. we don't care about
+      // setting level, dbounds, index, or the maxlevel
+      aabb->next = big_boxes;
+      big_boxes = aabb;
+    }
+  }
+
+  // for `n' objects, an n*n array of bits is used to record if those objects
+  // have been intersection-tested against each other yet. this array can
+  // grow large with high n, but oh well...
+  int tested_rowsize = (n+7) >> 3;      // number of bytes needed for n bits
+  unsigned char *tested = (unsigned char *) ALLOCA (n * tested_rowsize);
+  memset (tested,0,n * tested_rowsize);
+
+  // create a hash table to store all AABBs. each AABB may take up to 8 cells.
+  // we use chaining to resolve collisions, but we use a relatively large table
+  // to reduce the chance of collisions.
+
+  // compute hash table size sz to be a prime > 8*n
+  for (i=0; i<NUM_PRIMES; i++) {
+    if (prime[i] >= (8*n)) break;
+  }
+  if (i >= NUM_PRIMES) i = NUM_PRIMES-1;        // probably pointless
+  int sz = prime[i];
+
+  // allocate and initialize hash table node pointers
+  Node **table = (Node **) ALLOCA (sizeof(Node*) * sz);
+  for (i=0; i<sz; i++) table[i] = 0;
+
+  // add each AABB to the hash table (may need to add it to up to 8 cells)
+  for (aabb=first_aabb; aabb; aabb=aabb->next) {
+    int *dbounds = aabb->dbounds;
+    for (int xi = dbounds[0]; xi <= dbounds[1]; xi++) {
+      for (int yi = dbounds[2]; yi <= dbounds[3]; yi++) {
+        for (int zi = dbounds[4]; zi <= dbounds[5]; zi++) {
+          // get the hash index
+          unsigned long hi = getVirtualAddress (aabb->level,xi,yi,zi) % sz;
+          // add a new node to the hash table
+          Node *node = (Node*) ALLOCA (sizeof (Node));
+          node->x = xi;
+          node->y = yi;
+          node->z = zi;
+          node->aabb = aabb;
+          node->next = table[hi];
+          table[hi] = node;
+        }
+      }
+    }
+  }
+
+  // now that all AABBs are loaded into the hash table, we do the actual
+  // collision detection. for all AABBs, check for other AABBs in the
+  // same cells for collisions, and then check for other AABBs in all
+  // intersecting higher level cells.
+
+  int db[6];                    // discrete bounds at current level
+  for (aabb=first_aabb; aabb; aabb=aabb->next) {
+    // we are searching for collisions with aabb
+    for (i=0; i<6; i++) db[i] = aabb->dbounds[i];
+    for (int level = aabb->level; level <= maxlevel; level++) {
+      for (int xi = db[0]; xi <= db[1]; xi++) {
+        for (int yi = db[2]; yi <= db[3]; yi++) {
+          for (int zi = db[4]; zi <= db[5]; zi++) {
+            // get the hash index
+            unsigned long hi = getVirtualAddress (level,xi,yi,zi) % sz;
+            // search all nodes at this index
+            Node *node;
+            for (node = table[hi]; node; node=node->next) {
+              // node points to an AABB that may intersect aabb
+              if (node->aabb == aabb) continue;
+              if (node->aabb->level == level &&
+                  node->x == xi && node->y == yi && node->z == zi) {
+                // see if aabb and node->aabb have already been tested
+                // against each other
+                unsigned char mask;
+                if (aabb->index <= node->aabb->index) {
+                  i = (aabb->index * tested_rowsize)+(node->aabb->index >> 3);
+                  mask = 1 << (node->aabb->index & 7);
+                }
+                else {
+                  i = (node->aabb->index * tested_rowsize)+(aabb->index >> 3);
+                  mask = 1 << (aabb->index & 7);
+                }
+                dIASSERT (i >= 0 && i < (tested_rowsize*n));
+                if ((tested[i] & mask)==0) {
+                  collideAABBs (aabb->geom,node->aabb->geom,data,callback);
+                }
+                tested[i] |= mask;
+              }
+            }
+          }
+        }
+      }
+      // get the discrete bounds for the next level up
+      for (i=0; i<6; i++) db[i] >>= 1;
+    }
+  }
+
+  // every AABB in the normal list must now be intersected against every
+  // AABB in the big_boxes list. so let's hope there are not too many objects
+  // in the big_boxes list.
+  for (aabb=first_aabb; aabb; aabb=aabb->next) {
+    for (dxAABB *aabb2=big_boxes; aabb2; aabb2=aabb2->next) {
+      collideAABBs (aabb->geom,aabb2->geom,data,callback);
+    }
+  }
+
+  // intersected all AABBs in the big_boxes list together
+  for (aabb=big_boxes; aabb; aabb=aabb->next) {
+    for (dxAABB *aabb2=aabb->next; aabb2; aabb2=aabb2->next) {
+      collideAABBs (aabb->geom,aabb2->geom,data,callback);
+    }
+  }
+
+  lock_count--;
+}
+
+
+void dxHashSpace::collide2 (void *data, dxGeom *geom,
+                            dNearCallback *callback)
+{
+  dAASSERT (geom && callback);
+  
+  // this could take advantage of the hash structure to avoid
+  // O(n2) complexity, but it does not yet.
+  
+  lock_count++;
+  cleanGeoms();
+  geom->recomputeAABB();
+  
+  // intersect bounding boxes
+  for (dxGeom *g=first; g; g=g->next) {
+    if (GEOM_ENABLED(g)) collideAABBs (g,geom,data,callback);
+  }
+  
+  lock_count--;
+}
+
+//****************************************************************************
+// space functions
+
+dxSpace *dSimpleSpaceCreate (dxSpace *space)
+{
+  return new dxSimpleSpace (space);
+}
+
+
+dxSpace *dHashSpaceCreate (dxSpace *space)
+{
+  return new dxHashSpace (space);
+}
+
+
+void dHashSpaceSetLevels (dxSpace *space, int minlevel, int maxlevel)
+{
+  dAASSERT (space);
+  dUASSERT (minlevel <= maxlevel,"must have minlevel <= maxlevel");
+  dUASSERT (space->type == dHashSpaceClass,"argument must be a hash space");
+  dxHashSpace *hspace = (dxHashSpace*) space;
+  hspace->setLevels (minlevel,maxlevel);
+}
+
+
+void dHashSpaceGetLevels (dxSpace *space, int *minlevel, int *maxlevel)
+{
+  dAASSERT (space);
+  dUASSERT (space->type == dHashSpaceClass,"argument must be a hash space");
+  dxHashSpace *hspace = (dxHashSpace*) space;
+  hspace->getLevels (minlevel,maxlevel);
+}
+
+
+void dSpaceDestroy (dxSpace *space)
+{
+  dAASSERT (space);
+  dUASSERT (dGeomIsSpace(space),"argument not a space");
+  dGeomDestroy (space);
+}
+
+
+void dSpaceSetCleanup (dxSpace *space, int mode)
+{
+  dAASSERT (space);
+  dUASSERT (dGeomIsSpace(space),"argument not a space");
+  space->setCleanup (mode);
+}
+
+
+int dSpaceGetCleanup (dxSpace *space)
+{
+  dAASSERT (space);
+  dUASSERT (dGeomIsSpace(space),"argument not a space");
+  return space->getCleanup();
+}
+
+
+void dSpaceAdd (dxSpace *space, dxGeom *g)
+{
+  dAASSERT (space);
+  dUASSERT (dGeomIsSpace(space),"argument not a space");
+  CHECK_NOT_LOCKED (space);
+  space->add (g);
+}
+
+
+void dSpaceRemove (dxSpace *space, dxGeom *g)
+{
+  dAASSERT (space);
+  dUASSERT (dGeomIsSpace(space),"argument not a space");
+  CHECK_NOT_LOCKED (space);
+  space->remove (g);
+}
+
+
+int dSpaceQuery (dxSpace *space, dxGeom *g)
+{
+  dAASSERT (space);
+  dUASSERT (dGeomIsSpace(space),"argument not a space");
+  return space->query (g);
+}
+
+void dSpaceClean (dxSpace *space){
+  dAASSERT (space);
+  dUASSERT (dGeomIsSpace(space),"argument not a space");
+
+  space->cleanGeoms();
+}
+
+int dSpaceGetNumGeoms (dxSpace *space)
+{
+  dAASSERT (space);
+  dUASSERT (dGeomIsSpace(space),"argument not a space");
+  return space->getNumGeoms();
+}
+
+
+dGeomID dSpaceGetGeom (dxSpace *space, int i)
+{
+  dAASSERT (space);
+  dUASSERT (dGeomIsSpace(space),"argument not a space");
+  return space->getGeom (i);
+}
+
+
+void dSpaceCollide (dxSpace *space, void *data, dNearCallback *callback)
+{
+  dAASSERT (space && callback);
+  dUASSERT (dGeomIsSpace(space),"argument not a space");
+  space->collide (data,callback);
+}
+
+
+void dSpaceCollide2 (dxGeom *g1, dxGeom *g2, void *data,
+                     dNearCallback *callback)
+{
+  dAASSERT (g1 && g2 && callback);
+  dxSpace *s1,*s2;
+
+  // see if either geom is a space
+  if (IS_SPACE(g1)) s1 = (dxSpace*) g1; else s1 = 0;
+  if (IS_SPACE(g2)) s2 = (dxSpace*) g2; else s2 = 0;
+
+  // handle the four space/geom cases
+  if (s1) {
+    if (s2) {
+      // g1 and g2 are spaces.
+      if (s1==s2) {
+        // collide a space with itself --> interior collision
+        s1->collide (data,callback);
+      }
+      else {
+        // iterate through the space that has the fewest geoms, calling
+        // collide2 in the other space for each one.
+        if (s1->count < s2->count) {
+          for (dxGeom *g = s1->first; g; g=g->next) {
+            s2->collide2 (data,g,callback);
+          }
+        }
+        else {
+          for (dxGeom *g = s2->first; g; g=g->next) {
+            s1->collide2 (data,g,callback);
+          }
+        }
+      }
+    }
+    else {
+      // g1 is a space, g2 is a geom
+      s1->collide2 (data,g2,callback);
+    }
+  }
+  else {
+    if (s2) {
+      // g1 is a geom, g2 is a space
+      s2->collide2 (data,g1,callback);
+    }
+    else {
+      // g1 and g2 are geoms, call the callback directly
+      callback (data,g1,g2);
+    }
+  }
+}