Function check_vector_to_cylinder

physics/findintersection.cpp:1284–1431

check if a sphere intersects a face -- this can be optimized (only need 2d stuff after rotation)

// check if a sphere intersects a face -- this can be optimized (only need 2d stuff after rotation)
int check_vector_to_cylinder(vector *colp, vector *intp, float *col_dist, vector *wall_norm, const vector *p0,
                             const vector *p1, float rad, vector *ep0, vector *ep1) {
  matrix edge_orient;
  vector po0, po1;
  vector edgevec = *ep1 - *ep0;
  vector mvec;
  vector closest_pnt;

  float edge_len;
  float dist;
  float vector_len;
  float dist_from_origin;
  float dist_to_intersection;
  int i;
  int valid_hit = 0;

  vector mvec3d;
  float vector_len3d;

  float t[4];
  vector ivertex[4];

  int valid_t[4];
  float cole_dist[4];
  vector inte[4];

  mvec3d = *p1 - *p0;
  vector_len3d = vm_NormalizeVector(&mvec3d);

  edge_len = vm_NormalizeVector(&edgevec);

  vector init_normal;
  bool f_init_collide;

  if (!IsPointInCylinder(&init_normal, ep0, &edgevec, edge_len, rad, p0, &mvec3d, &f_init_collide)) {
    vm_VectorToMatrix(&edge_orient, &edgevec, nullptr, nullptr);

    po0 = (*p0 - *ep0) * edge_orient;
    po1 = (*p1 - *ep0) * edge_orient;

    po0.z = po1.z = 0.0;
    mvec = po1 - po0;
    vector_len = vm_NormalizeVector(&mvec);

    dist = -(mvec * po0);

    closest_pnt = po0 + dist * mvec;
    //	ASSERT(!(closest_pnt.x == 0.0 && closest_pnt.y == 0.0 && closest_pnt.z == 0)); -- why does this matter?

    dist_from_origin = vm_GetMagnitude(&closest_pnt);
    if (dist_from_origin >= rad)
      return 0;

    dist_to_intersection = sqrt(rad * rad - dist_from_origin * dist_from_origin);

    t[0] = (dist + dist_to_intersection) / vector_len; // (0.0 to 1.0) is on line
    if (t[0] >= 0.0 && t[0] <= 1.0) {
      valid_t[0] = 1;