Function check_vector_to_sphere_1

physics/findintersection.cpp:1174–1258

decide it it's close enough to hit determine if and where a vector intersects with a sphere vector defined by p0,p1 if there is an intersection this function returns 1, fills in intp, and col_dist else it returns 0 NOTE: Caller should account for the radius of the vector (i.e. no rad. for the vector is passed to this function -- the 2 radii are additive to it is trial and it saves 1 parameter

// NOTE:  Caller should account for the radius of the vector (i.e. no rad. for the vector is passed
//        to this function -- the 2 radii are additive to it is trial and it saves 1 parameter
int check_vector_to_sphere_1(vector *intp, float *col_dist, const vector *p0, const vector *p1, vector *sphere_pos,
                             float sphere_rad, bool f_correcting, bool f_init_collisions) {
  vector line_vec;            // Vector direction of line from p0 to p1
  vector normalized_line_vec; // Normalized line vector
  float mag_line;             // Length of the line

  vector point_to_center_vec;  // Vector from p0 to the center of the sphere
  vector closest_point;        // Location the sphere's centerpoint parallel projected onto the line
  float closest_point_dist;    // Distance from p0 to the closest_point
  float closest_mag_to_center; // Distance from the clostest_point to the center of the sphere

  float shorten; // How much to subtract from the closest_point_dist to get the actual intersection
                 // point

  ASSERT(sphere_rad > 0.0);

  // Get the vectors as usual
  line_vec = *p1 - *p0;
  point_to_center_vec = *sphere_pos - *p0;

  if (line_vec * point_to_center_vec <= 0.0f)
    return 0;

  // Get the magnitude and direction of the line vector
  normalized_line_vec = line_vec;
  mag_line = vm_NormalizeVector(&normalized_line_vec);

  // Compute the location of the point on the line that is perpendicular to the center of the sphere
  closest_point_dist = normalized_line_vec * point_to_center_vec;

  // We check for an initial hit, so if closest_point is negative distance, it was a miss (think about it)
  // Otherwise, make sure it is not any farther than would for a collision to happen
  if (closest_point_dist < 0.0 || closest_point_dist >= mag_line + sphere_rad)
    return 0;

  // Is the initial p0 position an intersection?  If so, warn us and collide immediately.
  if (point_to_center_vec * point_to_center_vec < sphere_rad * sphere_rad) {
    if (f_correcting) {
      /*
            // chrishack
            mprintf(0, "FVI WARNING: Start point is inside of a checked sphere %f %f\n",
                    point_to_center_vec * point_to_center_vec,
                    sphere_rad * sphere_rad);
      */
      // chrishack this movement intersection fix is a hack...  How do we do correct cylinder/vector interestion?
      vector n_ptc = point_to_center_vec;
      vm_NormalizeVector(&n_ptc);

      *intp =
          *p0 - n_ptc * (sphere_rad - (float)sqrt(sphere_rad * sphere_rad - point_to_center_vec * point_to_center_vec));

      *col_dist = 0.0;
      return 1;
    } else if (f_init_collisions) {
      *intp = *p0;
      *col_dist = 0.0;

      return 1;