/*************************************************************************
* *
* 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] = dMUL((p1[0]-p2[0]),d1);
c->normal[1] = dMUL((p1[1]-p2[1]),d1);
c->normal[2] = dMUL((p1[2]-p2[2]),d1);
dReal k = dMUL(REAL(0.5),(r2 - r1 - d));
c->pos[0] = p1[0] + dMUL(c->normal[0],k);
c->pos[1] = p1[1] + dMUL(c->normal[1],k);
c->pos[2] = p1[2] + dMUL(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-dMUL(uaub,uaub);
if (d <= REAL(0.0001)) {
// @@@ this needs to be made more robust
*alpha = 0;
*beta = 0;
}
else {
d = dRecip(d);
*alpha = dMUL((q1 + dMUL(uaub,q2)),d);
*beta = dMUL((dMUL(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.
EXPORT_C 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 = dDIV(da1,la);
a1a2[0] = dMUL(k,a1a2[0]);
a1a2[1] = dMUL(k,a1a2[1]);
a1a2[2] = dMUL(k,a1a2[2]);
SET3 (n,a1b1,-,a1a2);
if (dDOT(b1b2,n) >= 0) {
a1a2[0] = dMUL(k,a1a2[0]);
a1a2[1] = dMUL(k,a1a2[1]);
a1a2[2] = dMUL(k,a1a2[2]);
SET3 (cp1,a1,+,a1a2);
SET2 (cp2,b1);
return;
}
}
if (da2 >= 0 && da4 <= 0) {
k = dDIV(da2,la);
a1a2[0] = dMUL(k,a1a2[0]);
a1a2[1] = dMUL(k,a1a2[1]);
a1a2[2] = dMUL(k,a1a2[2]);
SET3 (n,a1b2,-,a1a2);
if (dDOT(b1b2,n) <= 0) {
a1a2[0] = dMUL(k,a1a2[0]);
a1a2[1] = dMUL(k,a1a2[1]);
a1a2[2] = dMUL(k,a1a2[2]);
SET3 (cp1,a1,+,a1a2);
SET2 (cp2,b2);
return;
}
}
lb = dDOT(b1b2,b1b2);
if (db1 <= 0 && db2 >= 0) {
k = -dDIV(db1,lb);
b1b2[0] = dMUL(k,b1b2[0]);
b1b2[1] = dMUL(k,b1b2[1]);
b1b2[2] = dMUL(k,b1b2[2]);
SET3 (n,-a1b1,-,b1b2);
if (dDOT(a1a2,n) >= 0) {
b1b2[0] = dMUL(k,b1b2[0]);
b1b2[1] = dMUL(k,b1b2[1]);
b1b2[2] = dMUL(k,b1b2[2]);
SET2 (cp1,a1);
SET3 (cp2,b1,+,b1b2);
return;
}
}
if (db3 <= 0 && db4 >= 0) {
k = -dDIV(db3,lb);
b1b2[0] = dMUL(k,b1b2[0]);
b1b2[1] = dMUL(k,b1b2[1]);
b1b2[2] = dMUL(k,b1b2[2]);
SET3 (n,-a2b1,-,b1b2);
if (dDOT(a1a2,n) <= 0) {
b1b2[0] = dMUL(k,b1b2[0]);
b1b2[1] = dMUL(k,b1b2[1]);
b1b2[2] = dMUL(k,b1b2[2]);
SET2 (cp1,a2);
SET3 (cp2,b1,+,b1b2);
return;
}
}
// it must be edge-edge
k = dDOT(a1a2,b1b2);
det = dMUL(la,lb) - dMUL(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 = dMUL((dMUL(lb,da1) - dMUL(k,db1)),det);
a1a2[0] = dMUL(alpha,a1a2[0]);
a1a2[1] = dMUL(alpha,a1a2[1]);
a1a2[2] = dMUL(alpha,a1a2[2]);
dReal beta = dMUL(( dMUL(k,da1) - dMUL(la,db1)),det);
b1b2[0] = dMUL(beta,b1b2[0]);
b1b2[1] = dMUL(beta,b1b2[1]);
b1b2[2] = dMUL(beta,b1b2[2]);
SET3 (cp1,a1,+,a1a2);
SET3 (cp2,b1,+,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] = REAL(-1.0);
}
else sign[i] = REAL(1.0);
}
// compute v^2
dVector3 v2;
v2[0] = dMUL(v[0],v[0]);
v2[1] = dMUL(v[1],v[1]);
v2[2] = dMUL(v[2],v[2]);
// compute the half-sides of the box
dReal h[3];
h[0] = dMUL(REAL(0.5),side[0]);
h[1] = dMUL(REAL(0.5),side[1]);
h[2] = dMUL(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)
const dReal tanchor_eps = REAL(2e-5f);
// 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] = dDIV((-h[i]-s[i]),v[i]);
}
else {
region[i] = (s[i] > h[i]);
tanchor[i] = dDIV((h[i]-s[i]),v[i]);
}
}
else {
region[i] = 0;
tanchor[i] = REAL(2.0); // 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 -= dMUL((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 = REAL(1.0);
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 = REAL(0.0);
for (i=0; i<3; i++) {
next_dd2dt += dMUL((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 = dDIV((next_dd2dt-dd2dt),(next_t - t));
t -= dDIV(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] = dDIV((h[i]-s[i]),v[i]);
region[i]++;
}
}
t = next_t;
dd2dt = next_dd2dt;
}
while (t < REAL(1.0));
t = REAL(1.0);
got_answer:
// compute closest point on the line
for (i=0; i<3; i++) lret[i] = p1[i] + dMUL(t,tmp[i]); // note: tmp=p2-p1
// compute closest point on the box
for (i=0; i<3; i++) {
tmp[i] = dMUL(sign[i],(s[i] + dMUL(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.
EXPORT_C 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 = dMUL(side1[0],REAL(0.5)); A2 = dMUL(side1[1],REAL(0.5)); A3 = dMUL(side1[2],REAL(0.5));
B1 = dMUL(side2[0],REAL(0.5)); B2 = dMUL(side2[1],REAL(0.5)); B3 = dMUL(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 + dMUL(B1,Q11) + dMUL(B2,Q12) + dMUL(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 + dMUL(B1,Q21) + dMUL(B2,Q22) + dMUL(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 + dMUL(B1,Q31) + dMUL(B2,Q32) + dMUL(B3,Q33))) return 0;
// separating axis = v1,v2,v3
if (dFabs(dDOT41(R2+0,p)) > (dMUL(A1,Q11) + dMUL(A2,Q21) + dMUL(A3,Q31) + B1)) return 0;
if (dFabs(dDOT41(R2+1,p)) > (dMUL(A1,Q12) + dMUL(A2,Q22) + dMUL(A3,Q32) + B2)) return 0;
if (dFabs(dDOT41(R2+2,p)) > (dMUL(A1,Q13) + dMUL(A2,Q23) + dMUL(A3,Q33) + B3)) return 0;
// separating axis = u1 x (v1,v2,v3)
if (dFabs(dMUL(pp[2],R21)-dMUL(pp[1],R31)) > dMUL(A2,Q31) + dMUL(A3,Q21) + dMUL(B2,Q13) + dMUL(B3,Q12)) return 0;
if (dFabs(dMUL(pp[2],R22)-dMUL(pp[1],R32)) > dMUL(A2,Q32) + dMUL(A3,Q22) + dMUL(B1,Q13) + dMUL(B3,Q11)) return 0;
if (dFabs(dMUL(pp[2],R23)-dMUL(pp[1],R33)) > dMUL(A2,Q33) + dMUL(A3,Q23) + dMUL(B1,Q12) + dMUL(B2,Q11)) return 0;
// separating axis = u2 x (v1,v2,v3)
if (dFabs(dMUL(pp[0],R31)-dMUL(pp[2],R11)) > dMUL(A1,Q31) + dMUL(A3,Q11) + dMUL(B2,Q23) + dMUL(B3,Q22)) return 0;
if (dFabs(dMUL(pp[0],R32)-dMUL(pp[2],R12)) > dMUL(A1,Q32) + dMUL(A3,Q12) + dMUL(B1,Q23) + dMUL(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(dMUL(pp[1],R11)-dMUL(pp[0],R21)) > dMUL(A1,Q21) + dMUL(A2,Q11) + dMUL(B2,Q33) + dMUL(B3,Q32)) return 0;
if (dFabs(dMUL(pp[1],R12)-dMUL(pp[0],R22)) > dMUL(A1,Q22) + dMUL(A2,Q12) + dMUL(B1,Q33) + dMUL(B3,Q31)) return 0;
if (dFabs(dMUL(pp[1],R13)-dMUL(pp[0],R23)) > dMUL(A1,Q23) + dMUL(A2,Q13) + dMUL(B1,Q32) + dMUL(B2,Q31)) return 0;
return 1;
}
//****************************************************************************
// other utility functions
EXPORT_C 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]-dMUL((vEpnt0[0]-vEpnt1[0]),dDIV(fDistance0,(fDistance0-fDistance1)));
vIntersectionPoint[1]= vEpnt0[1]-dMUL((vEpnt0[1]-vEpnt1[1]),dDIV(fDistance0,(fDistance0-fDistance1)));
vIntersectionPoint[2]= vEpnt0[2]-dMUL((vEpnt0[2]-vEpnt1[2]),dDIV(fDistance0,(fDistance0-fDistance1)));
// clamp correct edge to intersection point
if ( fDistance0 < REAL(0.0) )
{
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] -
dMUL((avArrayIn[i0][0]-avArrayIn[i1][0]),dDIV(fDistance0,(fDistance0-fDistance1)));
vIntersectionPoint[1]= avArrayIn[i0][1] -
dMUL((avArrayIn[i0][1]-avArrayIn[i1][1]),dDIV(fDistance0,(fDistance0-fDistance1)));
vIntersectionPoint[2]= avArrayIn[i0][2] -
dMUL((avArrayIn[i0][2]-avArrayIn[i1][2]),dDIV(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]) <= dMUL(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] -
dMUL((avArrayIn[i0][0]-avArrayIn[i1][0]),dDIV(fDistance0,(fDistance0-fDistance1)));
vIntersectionPoint[1]= avArrayIn[i0][1] -
dMUL((avArrayIn[i0][1]-avArrayIn[i1][1]),dDIV(fDistance0,(fDistance0-fDistance1)));
vIntersectionPoint[2]= avArrayIn[i0][2] -
dMUL((avArrayIn[i0][2]-avArrayIn[i1][2]),dDIV(fDistance0,(fDistance0-fDistance1)));
// emit intersection point
if (dVector3Length2(avArrayIn[i0]) <= dMUL(fRadius,fRadius))
{
avArrayOut[ctOut][0] = vIntersectionPoint[0];
avArrayOut[ctOut][1] = vIntersectionPoint[1];
avArrayOut[ctOut][2] = vIntersectionPoint[2];
ctOut++;
}
}
}
}