Function ClipEdge

editor/Erooms.cpp:1504–1539

Clips on edge of a polygon against another edge Parameters: normal - defines the plane in which these edgs lie v0,v1 - the edge to be clipped v2,v3 - is the edge clipped against newv - filled in with the intersection point

//					v2,v3 - is the edge clipped against
//					newv - filled in with the intersection point
void ClipEdge(vector *normal, vertex *v0, vertex *v1, vector *v2, vector *v3, vertex *newv) {
  float *vv0, *vv1, *vv2, *vv3;
  float k;
  int ii, jj;

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

  // Get pointers to elements of our vectors
  vv0 = (float *)&v0->vec;
  vv1 = (float *)&v1->vec;
  vv2 = (float *)v2;
  vv3 = (float *)v3;

  k = ((vv2[jj] - vv0[jj]) * (vv3[ii] - vv2[ii]) - (vv2[ii] - vv0[ii]) * (vv3[jj] - vv2[jj])) /
      ((vv1[jj] - vv0[jj]) * (vv3[ii] - vv2[ii]) - (vv1[ii] - vv0[ii]) * (vv3[jj] - vv2[jj]));

  // Deal w/ precision problems
  if (k < 0.0) {
    ASSERT((vm_VectorDistance(&v1->vec, &v0->vec) * -k) < POINT_TO_EDGE_EPSILON);
    k = 0.0;
  }
  if (k > 1.0) {
    ASSERT((vm_VectorDistance(&v1->vec, &v0->vec) * (k - 1.0)) < POINT_TO_EDGE_EPSILON);
    k = 1.0;
  }

  // Check for valid values of k
  ASSERT((k >= 0) && (k <= 1.0));

  newv->vec = v0->vec + (v1->vec - v0->vec) * k;

  newv->uvl.u = v0->uvl.u + (v1->uvl.u - v0->uvl.u) * k;
  newv->uvl.v = v0->uvl.v + (v1->uvl.v - v0->uvl.v) * k;
  newv->uvl.alpha = v0->uvl.alpha + ((v1->uvl.alpha - v0->uvl.alpha) * k);
}

// Finds a shared edge, if one exists, between two faces in the same room
// Parameters:	fp0,fp1 - pointers to the two faces