Function CheckPointAgainstEdge

editor/Erooms.cpp:1464–1497

Check if a point is inside, outside, or on an edge of a polygon Parameters: checkv - the point to be checked v1,v0 - the edge to check against. Two sequential verts in a clockwise polygon. normal - the surface normal of the polygon Returns: 1 if the point in inside the edge 0 if the point is on the edge -1 if the point is outside the edge

//				 0 if the point is on the edge
//				-1 if the point is outside the edge
int CheckPointAgainstEdge(vector *checkv, vector *v0, vector *v1, vector *normal) {
  int ii, jj;
  float edge_i, edge_j, check_i, check_j;
  float *vv0, *vv1, *checkvv;
  float edge_mag, dot;

  // Get the vertices for projection
  GetIJ(normal, &ii, &jj);

  // Get pointers to elements of our vectors
  vv0 = (float *)v0;
  vv1 = (float *)v1;
  checkvv = (float *)checkv;

  // Get 2d vector for edge
  edge_i = vv1[ii] - vv0[ii];
  edge_j = vv1[jj] - vv0[jj];
  edge_mag = sqrt(edge_i * edge_i + edge_j * edge_j);

  // Get 2d vector for check point
  check_i = checkvv[ii] - vv0[ii];
  check_j = checkvv[jj] - vv0[jj];

  // Now do the dot product to see if the check point is on the front
  dot = ((-edge_j * check_i) + (edge_i * check_j)) / edge_mag;

  // Check dot value and return appropriate code
  if (dot > POINT_TO_EDGE_EPSILON)
    return -1;
  else if (dot < -POINT_TO_EDGE_EPSILON)
    return 1;
  else
    return 0;
}

// Clips on edge of a polygon against another edge
// Parameters:	normal - defines the plane in which these edgs lie