adding ode source to /libraries

1 files changed, 612 insertions, 0 deletions

diff --git a/libraries/ode-0.9\/ode/src/collision_util.cpp b/libraries/ode-0.9\/ode/src/collision_util.cpp
new file mode 100755
index 0000000..460cc20
--- /dev/null
+++ b/libraries/ode-0.9\/ode/src/collision_util.cpp
@@ -0,0 +1,612 @@
+/*************************************************************************
+ *                                                                       *
+ * Open Dynamics Engine, Copyright (C) 2001,2002 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.                     *
+ *                                                                       *
+ *************************************************************************/
+
+/*
+
+some useful collision utility stuff. this includes some API utility
+functions that are defined in the public header files.
+
+*/
+
+#include <ode/common.h>
+#include <ode/collision.h>
+#include <ode/odemath.h>
+#include "collision_util.h"
+
+//****************************************************************************
+
+int dCollideSpheres (dVector3 p1, dReal r1,
+                     dVector3 p2, dReal r2, dContactGeom *c)
+{
+  // printf ("d=%.2f  (%.2f %.2f %.2f) (%.2f %.2f %.2f) r1=%.2f r2=%.2f\n",
+  //      d,p1[0],p1[1],p1[2],p2[0],p2[1],p2[2],r1,r2);
+
+  dReal d = dDISTANCE (p1,p2);
+  if (d > (r1 + r2)) return 0;
+  if (d <= 0) {
+    c->pos[0] = p1[0];
+    c->pos[1] = p1[1];
+    c->pos[2] = p1[2];
+    c->normal[0] = 1;
+    c->normal[1] = 0;
+    c->normal[2] = 0;
+    c->depth = r1 + r2;
+  }
+  else {
+    dReal d1 = dRecip (d);
+    c->normal[0] = (p1[0]-p2[0])*d1;
+    c->normal[1] = (p1[1]-p2[1])*d1;
+    c->normal[2] = (p1[2]-p2[2])*d1;
+    dReal k = REAL(0.5) * (r2 - r1 - d);
+    c->pos[0] = p1[0] + c->normal[0]*k;
+    c->pos[1] = p1[1] + c->normal[1]*k;
+    c->pos[2] = p1[2] + c->normal[2]*k;
+    c->depth = r1 + r2 - d;
+  }
+  return 1;
+}
+
+
+void dLineClosestApproach (const dVector3 pa, const dVector3 ua,
+                           const dVector3 pb, const dVector3 ub,
+                           dReal *alpha, dReal *beta)
+{
+  dVector3 p;
+  p[0] = pb[0] - pa[0];
+  p[1] = pb[1] - pa[1];
+  p[2] = pb[2] - pa[2];
+  dReal uaub = dDOT(ua,ub);
+  dReal q1 =  dDOT(ua,p);
+  dReal q2 = -dDOT(ub,p);
+  dReal d = 1-uaub*uaub;
+  if (d <= REAL(0.0001)) {
+    // @@@ this needs to be made more robust
+    *alpha = 0;
+    *beta  = 0;
+  }
+  else {
+    d = dRecip(d);
+    *alpha = (q1 + uaub*q2)*d;
+    *beta  = (uaub*q1 + q2)*d;
+  }
+}
+
+
+// given two line segments A and B with endpoints a1-a2 and b1-b2, return the
+// points on A and B that are closest to each other (in cp1 and cp2).
+// in the case of parallel lines where there are multiple solutions, a
+// solution involving the endpoint of at least one line will be returned.
+// this will work correctly for zero length lines, e.g. if a1==a2 and/or
+// b1==b2.
+//
+// the algorithm works by applying the voronoi clipping rule to the features
+// of the line segments. the three features of each line segment are the two
+// endpoints and the line between them. the voronoi clipping rule states that,
+// for feature X on line A and feature Y on line B, the closest points PA and
+// PB between X and Y are globally the closest points if PA is in V(Y) and
+// PB is in V(X), where V(X) is the voronoi region of X.
+
+void dClosestLineSegmentPoints (const dVector3 a1, const dVector3 a2,
+                                const dVector3 b1, const dVector3 b2,
+                                dVector3 cp1, dVector3 cp2)
+{
+  dVector3 a1a2,b1b2,a1b1,a1b2,a2b1,a2b2,n;
+  dReal la,lb,k,da1,da2,da3,da4,db1,db2,db3,db4,det;
+
+#define SET2(a,b) a[0]=b[0]; a[1]=b[1]; a[2]=b[2];
+#define SET3(a,b,op,c) a[0]=b[0] op c[0]; a[1]=b[1] op c[1]; a[2]=b[2] op c[2];
+
+  // check vertex-vertex features
+
+  SET3 (a1a2,a2,-,a1);
+  SET3 (b1b2,b2,-,b1);
+  SET3 (a1b1,b1,-,a1);
+  da1 = dDOT(a1a2,a1b1);
+  db1 = dDOT(b1b2,a1b1);
+  if (da1 <= 0 && db1 >= 0) {
+    SET2 (cp1,a1);
+    SET2 (cp2,b1);
+    return;
+  }
+
+  SET3 (a1b2,b2,-,a1);
+  da2 = dDOT(a1a2,a1b2);
+  db2 = dDOT(b1b2,a1b2);
+  if (da2 <= 0 && db2 <= 0) {
+    SET2 (cp1,a1);
+    SET2 (cp2,b2);
+    return;
+  }
+
+  SET3 (a2b1,b1,-,a2);
+  da3 = dDOT(a1a2,a2b1);
+  db3 = dDOT(b1b2,a2b1);
+  if (da3 >= 0 && db3 >= 0) {
+    SET2 (cp1,a2);
+    SET2 (cp2,b1);
+    return;
+  }
+
+  SET3 (a2b2,b2,-,a2);
+  da4 = dDOT(a1a2,a2b2);
+  db4 = dDOT(b1b2,a2b2);
+  if (da4 >= 0 && db4 <= 0) {
+    SET2 (cp1,a2);
+    SET2 (cp2,b2);
+    return;
+  }
+
+  // check edge-vertex features.
+  // if one or both of the lines has zero length, we will never get to here,
+  // so we do not have to worry about the following divisions by zero.
+
+  la = dDOT(a1a2,a1a2);
+  if (da1 >= 0 && da3 <= 0) {
+    k = da1 / la;
+    SET3 (n,a1b1,-,k*a1a2);
+    if (dDOT(b1b2,n) >= 0) {
+      SET3 (cp1,a1,+,k*a1a2);
+      SET2 (cp2,b1);
+      return;
+    }
+  }
+
+  if (da2 >= 0 && da4 <= 0) {
+    k = da2 / la;
+    SET3 (n,a1b2,-,k*a1a2);
+    if (dDOT(b1b2,n) <= 0) {
+      SET3 (cp1,a1,+,k*a1a2);
+      SET2 (cp2,b2);
+      return;
+    }
+  }
+
+  lb = dDOT(b1b2,b1b2);
+  if (db1 <= 0 && db2 >= 0) {
+    k = -db1 / lb;
+    SET3 (n,-a1b1,-,k*b1b2);
+    if (dDOT(a1a2,n) >= 0) {
+      SET2 (cp1,a1);
+      SET3 (cp2,b1,+,k*b1b2);
+      return;
+    }
+  }
+
+  if (db3 <= 0 && db4 >= 0) {
+    k = -db3 / lb;
+    SET3 (n,-a2b1,-,k*b1b2);
+    if (dDOT(a1a2,n) <= 0) {
+      SET2 (cp1,a2);
+      SET3 (cp2,b1,+,k*b1b2);
+      return;
+    }
+  }
+
+  // it must be edge-edge
+
+  k = dDOT(a1a2,b1b2);
+  det = la*lb - k*k;
+  if (det <= 0) {
+    // this should never happen, but just in case...
+    SET2(cp1,a1);
+    SET2(cp2,b1);
+    return;
+  }
+  det = dRecip (det);
+  dReal alpha = (lb*da1 -  k*db1) * det;
+  dReal beta  = ( k*da1 - la*db1) * det;
+  SET3 (cp1,a1,+,alpha*a1a2);
+  SET3 (cp2,b1,+,beta*b1b2);
+
+# undef SET2
+# undef SET3
+}
+
+
+// a simple root finding algorithm is used to find the value of 't' that
+// satisfies:
+//              d|D(t)|^2/dt = 0
+// where:
+//              |D(t)| = |p(t)-b(t)|
+// where p(t) is a point on the line parameterized by t:
+//              p(t) = p1 + t*(p2-p1)
+// and b(t) is that same point clipped to the boundary of the box. in box-
+// relative coordinates d|D(t)|^2/dt is the sum of three x,y,z components
+// each of which looks like this:
+//
+//          t_lo     /
+//            ______/    -->t
+//           /     t_hi
+//          /
+//
+// t_lo and t_hi are the t values where the line passes through the planes
+// corresponding to the sides of the box. the algorithm computes d|D(t)|^2/dt
+// in a piecewise fashion from t=0 to t=1, stopping at the point where
+// d|D(t)|^2/dt crosses from negative to positive.
+
+void dClosestLineBoxPoints (const dVector3 p1, const dVector3 p2,
+                            const dVector3 c, const dMatrix3 R,
+                            const dVector3 side,
+                            dVector3 lret, dVector3 bret)
+{
+  int i;
+
+  // compute the start and delta of the line p1-p2 relative to the box.
+  // we will do all subsequent computations in this box-relative coordinate
+  // system. we have to do a translation and rotation for each point.
+  dVector3 tmp,s,v;
+  tmp[0] = p1[0] - c[0];
+  tmp[1] = p1[1] - c[1];
+  tmp[2] = p1[2] - c[2];
+  dMULTIPLY1_331 (s,R,tmp);
+  tmp[0] = p2[0] - p1[0];
+  tmp[1] = p2[1] - p1[1];
+  tmp[2] = p2[2] - p1[2];
+  dMULTIPLY1_331 (v,R,tmp);
+
+  // mirror the line so that v has all components >= 0
+  dVector3 sign;
+  for (i=0; i<3; i++) {
+    if (v[i] < 0) {
+      s[i] = -s[i];
+      v[i] = -v[i];
+      sign[i] = -1;
+    }
+    else sign[i] = 1;
+  }
+
+  // compute v^2
+  dVector3 v2;
+  v2[0] = v[0]*v[0];
+  v2[1] = v[1]*v[1];
+  v2[2] = v[2]*v[2];
+
+  // compute the half-sides of the box
+  dReal h[3];
+  h[0] = REAL(0.5) * side[0];
+  h[1] = REAL(0.5) * side[1];
+  h[2] = REAL(0.5) * side[2];
+
+  // region is -1,0,+1 depending on which side of the box planes each
+  // coordinate is on. tanchor is the next t value at which there is a
+  // transition, or the last one if there are no more.
+  int region[3];
+  dReal tanchor[3];
+
+  // Denormals are a problem, because we divide by v[i], and then 
+  // multiply that by 0. Alas, infinity times 0 is infinity (!)
+  // We also use v2[i], which is v[i] squared. Here's how the epsilons 
+  // are chosen:
+  // float epsilon = 1.175494e-038 (smallest non-denormal number)
+  // double epsilon = 2.225074e-308 (smallest non-denormal number)
+  // For single precision, choose an epsilon such that v[i] squared is 
+  // not a denormal; this is for performance.
+  // For double precision, choose an epsilon such that v[i] is not a 
+  // denormal; this is for correctness. (Jon Watte on mailinglist)
+
+#if defined( dSINGLE )
+  const dReal tanchor_eps = REAL(1e-19);
+#else
+  const dReal tanchor_eps = REAL(1e-307);
+#endif
+
+  // find the region and tanchor values for p1
+  for (i=0; i<3; i++) {
+    if (v[i] > tanchor_eps) {
+      if (s[i] < -h[i]) {
+        region[i] = -1;
+        tanchor[i] = (-h[i]-s[i])/v[i];
+      }
+      else {
+        region[i] = (s[i] > h[i]);
+        tanchor[i] = (h[i]-s[i])/v[i];
+      }
+    }
+    else {
+      region[i] = 0;
+      tanchor[i] = 2;           // this will never be a valid tanchor
+    }
+  }
+
+  // compute d|d|^2/dt for t=0. if it's >= 0 then p1 is the closest point
+  dReal t=0;
+  dReal dd2dt = 0;
+  for (i=0; i<3; i++) dd2dt -= (region[i] ? v2[i] : 0) * tanchor[i];
+  if (dd2dt >= 0) goto got_answer;
+
+  do {
+    // find the point on the line that is at the next clip plane boundary
+    dReal next_t = 1;
+    for (i=0; i<3; i++) {
+      if (tanchor[i] > t && tanchor[i] < 1 && tanchor[i] < next_t)
+        next_t = tanchor[i];
+    }
+
+    // compute d|d|^2/dt for the next t
+    dReal next_dd2dt = 0;
+    for (i=0; i<3; i++) {
+      next_dd2dt += (region[i] ? v2[i] : 0) * (next_t - tanchor[i]);
+    }
+
+    // if the sign of d|d|^2/dt has changed, solution = the crossover point
+    if (next_dd2dt >= 0) {
+      dReal m = (next_dd2dt-dd2dt)/(next_t - t);
+      t -= dd2dt/m;
+      goto got_answer;
+    }
+
+    // advance to the next anchor point / region
+    for (i=0; i<3; i++) {
+      if (tanchor[i] == next_t) {
+        tanchor[i] = (h[i]-s[i])/v[i];
+        region[i]++;
+      }
+    }
+    t = next_t;
+    dd2dt = next_dd2dt;
+  }
+  while (t < 1);
+  t = 1;
+
+  got_answer:
+
+  // compute closest point on the line
+  for (i=0; i<3; i++) lret[i] = p1[i] + t*tmp[i];       // note: tmp=p2-p1
+
+  // compute closest point on the box
+  for (i=0; i<3; i++) {
+    tmp[i] = sign[i] * (s[i] + t*v[i]);
+    if (tmp[i] < -h[i]) tmp[i] = -h[i];
+    else if (tmp[i] > h[i]) tmp[i] = h[i];
+  }
+  dMULTIPLY0_331 (s,R,tmp);
+  for (i=0; i<3; i++) bret[i] = s[i] + c[i];
+}
+
+
+// given boxes (p1,R1,side1) and (p1,R1,side1), return 1 if they intersect
+// or 0 if not.
+
+int dBoxTouchesBox (const dVector3 p1, const dMatrix3 R1,
+                    const dVector3 side1, const dVector3 p2,
+                    const dMatrix3 R2, const dVector3 side2)
+{
+  // two boxes are disjoint if (and only if) there is a separating axis
+  // perpendicular to a face from one box or perpendicular to an edge from
+  // either box. the following tests are derived from:
+  //    "OBB Tree: A Hierarchical Structure for Rapid Interference Detection",
+  //    S.Gottschalk, M.C.Lin, D.Manocha., Proc of ACM Siggraph 1996.
+
+  // Rij is R1'*R2, i.e. the relative rotation between R1 and R2.
+  // Qij is abs(Rij)
+  dVector3 p,pp;
+  dReal A1,A2,A3,B1,B2,B3,R11,R12,R13,R21,R22,R23,R31,R32,R33,
+    Q11,Q12,Q13,Q21,Q22,Q23,Q31,Q32,Q33;
+
+  // get vector from centers of box 1 to box 2, relative to box 1
+  p[0] = p2[0] - p1[0];
+  p[1] = p2[1] - p1[1];
+  p[2] = p2[2] - p1[2];
+  dMULTIPLY1_331 (pp,R1,p);             // get pp = p relative to body 1
+
+  // get side lengths / 2
+  A1 = side1[0]*REAL(0.5); A2 = side1[1]*REAL(0.5); A3 = side1[2]*REAL(0.5);
+  B1 = side2[0]*REAL(0.5); B2 = side2[1]*REAL(0.5); B3 = side2[2]*REAL(0.5);
+
+  // for the following tests, excluding computation of Rij, in the worst case,
+  // 15 compares, 60 adds, 81 multiplies, and 24 absolutes.
+  // notation: R1=[u1 u2 u3], R2=[v1 v2 v3]
+
+  // separating axis = u1,u2,u3
+  R11 = dDOT44(R1+0,R2+0); R12 = dDOT44(R1+0,R2+1); R13 = dDOT44(R1+0,R2+2);
+  Q11 = dFabs(R11); Q12 = dFabs(R12); Q13 = dFabs(R13);
+  if (dFabs(pp[0]) > (A1 + B1*Q11 + B2*Q12 + B3*Q13)) return 0;
+  R21 = dDOT44(R1+1,R2+0); R22 = dDOT44(R1+1,R2+1); R23 = dDOT44(R1+1,R2+2);
+  Q21 = dFabs(R21); Q22 = dFabs(R22); Q23 = dFabs(R23);
+  if (dFabs(pp[1]) > (A2 + B1*Q21 + B2*Q22 + B3*Q23)) return 0;
+  R31 = dDOT44(R1+2,R2+0); R32 = dDOT44(R1+2,R2+1); R33 = dDOT44(R1+2,R2+2);
+  Q31 = dFabs(R31); Q32 = dFabs(R32); Q33 = dFabs(R33);
+  if (dFabs(pp[2]) > (A3 + B1*Q31 + B2*Q32 + B3*Q33)) return 0;
+
+  // separating axis = v1,v2,v3
+  if (dFabs(dDOT41(R2+0,p)) > (A1*Q11 + A2*Q21 + A3*Q31 + B1)) return 0;
+  if (dFabs(dDOT41(R2+1,p)) > (A1*Q12 + A2*Q22 + A3*Q32 + B2)) return 0;
+  if (dFabs(dDOT41(R2+2,p)) > (A1*Q13 + A2*Q23 + A3*Q33 + B3)) return 0;
+
+  // separating axis = u1 x (v1,v2,v3)
+  if (dFabs(pp[2]*R21-pp[1]*R31) > A2*Q31 + A3*Q21 + B2*Q13 + B3*Q12) return 0;
+  if (dFabs(pp[2]*R22-pp[1]*R32) > A2*Q32 + A3*Q22 + B1*Q13 + B3*Q11) return 0;
+  if (dFabs(pp[2]*R23-pp[1]*R33) > A2*Q33 + A3*Q23 + B1*Q12 + B2*Q11) return 0;
+
+  // separating axis = u2 x (v1,v2,v3)
+  if (dFabs(pp[0]*R31-pp[2]*R11) > A1*Q31 + A3*Q11 + B2*Q23 + B3*Q22) return 0;
+  if (dFabs(pp[0]*R32-pp[2]*R12) > A1*Q32 + A3*Q12 + B1*Q23 + B3*Q21) return 0;
+  if (dFabs(pp[0]*R33-pp[2]*R13) > A1*Q33 + A3*Q13 + B1*Q22 + B2*Q21) return 0;
+
+  // separating axis = u3 x (v1,v2,v3)
+  if (dFabs(pp[1]*R11-pp[0]*R21) > A1*Q21 + A2*Q11 + B2*Q33 + B3*Q32) return 0;
+  if (dFabs(pp[1]*R12-pp[0]*R22) > A1*Q22 + A2*Q12 + B1*Q33 + B3*Q31) return 0;
+  if (dFabs(pp[1]*R13-pp[0]*R23) > A1*Q23 + A2*Q13 + B1*Q32 + B2*Q31) return 0;
+
+  return 1;
+}
+
+//****************************************************************************
+// other utility functions
+
+void dInfiniteAABB (dxGeom *geom, dReal aabb[6])
+{
+  aabb[0] = -dInfinity;
+  aabb[1] = dInfinity;
+  aabb[2] = -dInfinity;
+  aabb[3] = dInfinity;
+  aabb[4] = -dInfinity;
+  aabb[5] = dInfinity;
+}
+
+
+//****************************************************************************
+// Helpers for Croteam's collider - by Nguyen Binh
+
+int dClipEdgeToPlane( dVector3 &vEpnt0, dVector3 &vEpnt1, const dVector4& plPlane)
+{
+        // calculate distance of edge points to plane
+        dReal fDistance0 = dPointPlaneDistance(  vEpnt0 ,plPlane );
+        dReal fDistance1 = dPointPlaneDistance(  vEpnt1 ,plPlane );
+
+        // if both points are behind the plane
+        if ( fDistance0 < 0 && fDistance1 < 0 ) 
+        {
+                // do nothing
+                return 0;
+                // if both points in front of the plane
+        } 
+        else if ( fDistance0 > 0 && fDistance1 > 0 ) 
+        {
+                // accept them
+                return 1;
+                // if we have edge/plane intersection
+        } else if ((fDistance0 > 0 && fDistance1 < 0) || ( fDistance0 < 0 && fDistance1 > 0)) 
+        {
+
+                // find intersection point of edge and plane
+                dVector3 vIntersectionPoint;
+                vIntersectionPoint[0]= vEpnt0[0]-(vEpnt0[0]-vEpnt1[0])*fDistance0/(fDistance0-fDistance1);
+                vIntersectionPoint[1]= vEpnt0[1]-(vEpnt0[1]-vEpnt1[1])*fDistance0/(fDistance0-fDistance1);
+                vIntersectionPoint[2]= vEpnt0[2]-(vEpnt0[2]-vEpnt1[2])*fDistance0/(fDistance0-fDistance1);
+
+                // clamp correct edge to intersection point
+                if ( fDistance0 < 0 ) 
+                {
+                        dVector3Copy(vIntersectionPoint,vEpnt0);
+                } else 
+                {
+                        dVector3Copy(vIntersectionPoint,vEpnt1);
+                }
+                return 1;
+        }
+        return 1;
+}
+
+// clip polygon with plane and generate new polygon points
+void             dClipPolyToPlane( const dVector3 avArrayIn[], const int ctIn, 
+                                                          dVector3 avArrayOut[], int &ctOut, 
+                                                          const dVector4 &plPlane )
+{
+        // start with no output points
+        ctOut = 0;
+
+        int i0 = ctIn-1;
+
+        // for each edge in input polygon
+        for (int i1=0; i1<ctIn; i0=i1, i1++) {
+
+
+                // calculate distance of edge points to plane
+                dReal fDistance0 = dPointPlaneDistance(  avArrayIn[i0],plPlane );
+                dReal fDistance1 = dPointPlaneDistance(  avArrayIn[i1],plPlane );
+
+                // if first point is in front of plane
+                if( fDistance0 >= 0 ) {
+                        // emit point
+                        avArrayOut[ctOut][0] = avArrayIn[i0][0];
+                        avArrayOut[ctOut][1] = avArrayIn[i0][1];
+                        avArrayOut[ctOut][2] = avArrayIn[i0][2];
+                        ctOut++;
+                }
+
+                // if points are on different sides
+                if( (fDistance0 > 0 && fDistance1 < 0) || ( fDistance0 < 0 && fDistance1 > 0) ) {
+
+                        // find intersection point of edge and plane
+                        dVector3 vIntersectionPoint;
+                        vIntersectionPoint[0]= avArrayIn[i0][0] - 
+                                (avArrayIn[i0][0]-avArrayIn[i1][0])*fDistance0/(fDistance0-fDistance1);
+                        vIntersectionPoint[1]= avArrayIn[i0][1] - 
+                                (avArrayIn[i0][1]-avArrayIn[i1][1])*fDistance0/(fDistance0-fDistance1);
+                        vIntersectionPoint[2]= avArrayIn[i0][2] - 
+                                (avArrayIn[i0][2]-avArrayIn[i1][2])*fDistance0/(fDistance0-fDistance1);
+
+                        // emit intersection point
+                        avArrayOut[ctOut][0] = vIntersectionPoint[0];
+                        avArrayOut[ctOut][1] = vIntersectionPoint[1];
+                        avArrayOut[ctOut][2] = vIntersectionPoint[2];
+                        ctOut++;
+                }
+        }
+
+}
+
+void             dClipPolyToCircle(const dVector3 avArrayIn[], const int ctIn, 
+                                                           dVector3 avArrayOut[], int &ctOut, 
+                                                           const dVector4 &plPlane ,dReal fRadius)
+{
+        // start with no output points
+        ctOut = 0;
+
+        int i0 = ctIn-1;
+
+        // for each edge in input polygon
+        for (int i1=0; i1<ctIn; i0=i1, i1++) 
+        {
+                // calculate distance of edge points to plane
+                dReal fDistance0 = dPointPlaneDistance(  avArrayIn[i0],plPlane );
+                dReal fDistance1 = dPointPlaneDistance(  avArrayIn[i1],plPlane );
+
+                // if first point is in front of plane
+                if( fDistance0 >= 0 ) 
+                {
+                        // emit point
+                        if (dVector3Length2(avArrayIn[i0]) <= fRadius*fRadius)
+                        {
+                                avArrayOut[ctOut][0] = avArrayIn[i0][0];
+                                avArrayOut[ctOut][1] = avArrayIn[i0][1];
+                                avArrayOut[ctOut][2] = avArrayIn[i0][2];
+                                ctOut++;
+                        }
+                }
+
+                // if points are on different sides
+                if( (fDistance0 > 0 && fDistance1 < 0) || ( fDistance0 < 0 && fDistance1 > 0) ) 
+                {
+
+                        // find intersection point of edge and plane
+                        dVector3 vIntersectionPoint;
+                        vIntersectionPoint[0]= avArrayIn[i0][0] - 
+                                (avArrayIn[i0][0]-avArrayIn[i1][0])*fDistance0/(fDistance0-fDistance1);
+                        vIntersectionPoint[1]= avArrayIn[i0][1] - 
+                                (avArrayIn[i0][1]-avArrayIn[i1][1])*fDistance0/(fDistance0-fDistance1);
+                        vIntersectionPoint[2]= avArrayIn[i0][2] - 
+                                (avArrayIn[i0][2]-avArrayIn[i1][2])*fDistance0/(fDistance0-fDistance1);
+
+                        // emit intersection point
+                        if (dVector3Length2(avArrayIn[i0]) <= fRadius*fRadius)
+                        {
+                                avArrayOut[ctOut][0] = vIntersectionPoint[0];
+                                avArrayOut[ctOut][1] = vIntersectionPoint[1];
+                                avArrayOut[ctOut][2] = vIntersectionPoint[2];
+                                ctOut++;
+                        }
+                }
+        }       
+}
+