Function ComputeDebugVisFaceUpperLeft

Descent3/renderobject.cpp:772–858

Given a face, computes the upper left corner of the face

}
// Given a face, computes the upper left corner of the face
void ComputeDebugVisFaceUpperLeft(room *rp, face *fp, vector *upper_left, float *xdiff, float *ydiff, vector *center) {
  matrix face_matrix, trans_matrix;
  vector fvec;
  vector avg_vert;
  vector verts[MAX_VERTS_PER_FACE];
  vector rot_vert;
  int i;

  // find the center point of this face
  vm_MakeZero(&avg_vert);
  for (i = 0; i < fp->num_verts; i++)
    avg_vert += rp->verts[fp->face_verts[i]];
  avg_vert /= fp->num_verts;
  // Make the orientation matrix
  // Reverse the normal because we're looking "at" the face, not from it
  fvec = -fp->normal;

  vm_VectorToMatrix(&face_matrix, &fvec, NULL, NULL);
  // Make the transformation matrix

  angvec avec;
  vm_ExtractAnglesFromMatrix(&avec, &face_matrix);
  vm_AnglesToMatrix(&trans_matrix, avec.p, avec.h, avec.b);

  // Rotate all the points
  for (i = 0; i < fp->num_verts; i++) {
    vector vert = rp->verts[fp->face_verts[i]];

    vert -= avg_vert;
    vm_MatrixMulVector(&rot_vert, &vert, &trans_matrix);
    verts[i] = rot_vert;
  }
  // Find left most point
  int leftmost_point = -1;
  float leftmost_x = 900000.00f; // a big number
  for (i = 0; i < fp->num_verts; i++) {
    if (verts[i].x < leftmost_x) {
      leftmost_point = i;
      leftmost_x = verts[i].x;
    }
  }
  ASSERT(leftmost_point != -1);
  // Find top most point
  int topmost_point = -1;
  float topmost_y = -900000.0f; // a big number
  for (i = 0; i < fp->num_verts; i++) {
    if (verts[i].y > topmost_y) {
      topmost_point = i;
      topmost_y = verts[i].y;
    }
  }
  ASSERT(topmost_point != -1);
  // Find right most point
  int rightmost_point = -1;
  float rightmost_x = -900000.00f; // a big number
  for (i = 0; i < fp->num_verts; i++) {
    if (verts[i].x > rightmost_x) {
      rightmost_point = i;