Check against the last motion of particles and segment Ignore radius of each particle

class Checker_ParticleMvt0 implements Checker{
 final IntersectionFinder _intf = new IntersectionFinderXY();
 final _v0 = new Vector3.zero();
 final _v1 = new Vector3.zero();
 final _v2 = new Vector3.zero();
 final _v3 = new Vector3.zero();
 /// Returns whether two particles A ([psA] + [iA]) and B [psB] + [iB]) intersect
 /// [psA.collide[iA]] and [psB.collide[iB]] are set to true if collision.
 /// Doesn't check if provided particles are the same or part of same group,... should be done before calling.
 /// * **Ignore radius of each particle**
 /// * check against the movement of the particles A and B (previous -> current)
 collideParticleParticle(Particles psA, int iA, Particles psB, int iB, Vector4 acol) {
   //var b = intf.sphere_sphere(psA.position3d[iA], psA.radius[iA], psB.position3d[iB], psA.radius[iB]);
   var pa0 = psA.position3dPrevious[iA];
   var pa1 = psA.position3d[iA];
   var pb0 = psB.position3dPrevious[iB];
   var pb1 = psB.position3d[iB];
   if (pa0 == pa1){
     pa0 = _v0.setFrom(pa0);
     pa0.x = pa0.x - psA.radius[iA];
     pa1 = _v1.setFrom(pb1);
     pa1.x = pa1.x + psA.radius[iA];
   }
   if (pb0 == pb1){
     pb0 = _v2.setFrom(pb0);
     pb0.x = pb0.x - psB.radius[iB];
     pb1 = _v3.setFrom(pb1);
     pb1.x = pb1.x + psB.radius[iB];
   }
   var b = _intf.segment_segment(pa0, pa1, pb0, pb1, acol);
   if (b) {
     psA.collide[iA] = -1;
     psB.collide[iB] = -1;
   }
   return b;
 }

 /// Returns whether the provided particle A and the segment from B intersect
 /// Doesn't check if provided particles are the same or part of same group,... should be done before calling.
 /// * **Ignore radius of each particle**
 /// * check against the movement of the particle A (previous -> current)
 /// * **Ignore movement of segment**, only check against last position of the segment
 collideParticleSegment(Particles psA, int iA, Segment s, Vector4 scol) {
   var b = false;
   //b = b || collideParticleSegment0(psA.position3dPrevious[iA], psA.position3d[iA], psA.radius[iA], s.ps.position3dPrevious[s.i1], s.ps.position3d[s.i1], s.ps.position3dPrevious[s.i2], s.ps.position3d[s.i2], intf, ci);
   //b = b || intf.segment_sphere(s.ps.position3d[s.i1], s.ps.position3d[s.i2], psA.position3d[iA], psA.radius[iA]);
   var pa0 = psA.position3dPrevious[iA];
   var pa1 = psA.position3d[iA];
   // create a segment perpendicular to input segment for immobile particle
   if (pa0 == pa1){
     _v3.setFrom(s.ps.position3d[s.i1]).sub(s.ps.position3d[s.i2]);
     _v3.normalize().scale(psA.radius[iA]);
     var t = _v3.x;
     _v3.x = _v3.y;
     _v3.y = t;
     pa0 = _v0.setFrom(pa0).sub(_v3);
     pa1 = _v1.setFrom(pa0).add(_v3);
   }
   b = b || _intf.segment_segment(pa0, pa1, s.ps.position3d[s.i1], s.ps.position3d[s.i2], scol);

   if (b) {
     psA.collide[iA] = -1;
     s.collide = -1;
   }
   return b;
 }
}