Function BSPRayOccluded

Descent3/bsp.cpp:1149–1197

static int si;

int BSPRayOccluded(vector *line_start, vector *line_end, bspnode *start_node) {
  si = 0;
  vector start, end;
  bspnode *node;

  PUSH_BSP_RAY(*line_start, *line_end, start_node);

  while (si > 0) {
    POP_BSP_RAY();
    while (node->type == BSP_NODE) {
      float dist1 = node->plane.a * start.x + node->plane.b * start.y + node->plane.c * start.z + node->plane.d;
      float dist2 = node->plane.a * end.x + node->plane.b * end.y + node->plane.c * end.z + node->plane.d;

      if (dist1 >= 0 && dist2 >= 0) {
        node = (bspnode *)node->front;
      } else if (dist1 < 0 && dist2 < 0) {
        node = (bspnode *)node->back;
      } else {
        vector mid, delta;
        float t;

        // Generate split point
        t = dist1 / (dist1 - dist2);
        delta = end - start;
        mid = start + (t * delta);
        if (BSPPointInPolygon(&mid, node))
          return 1;

        // vm_NormalizeVectorFast (&delta);

        vector mid1 = mid; //-(delta*BSP_EPSILON);
        vector mid2 = mid; //+(delta*BSP_EPSILON);

        if (dist1 >= 0.0) {
          PUSH_BSP_RAY(mid1, end, (bspnode *)node->back);
          PUSH_BSP_RAY(start, mid2, (bspnode *)node->front);
        } else {
          PUSH_BSP_RAY(mid2, end, (bspnode *)node->front);
          PUSH_BSP_RAY(start, mid1, (bspnode *)node->back);
        }

        goto break_out;
      }
    }
  break_out:;
  }

  return 0;
}

// Initializes some variables for the indoor bsp tree
void InitDefaultBSP() {