Function gather_grid

tutorials/common/scenegraph/scenegraph.cpp:1462–1518

  }

  void gather_grid(RTCGeometry geom, avector<Vec3fa>& positions, size_t width, size_t height, unsigned int* indices, avector<Vec3fa>& vertices, unsigned int edgey)
  {
    //        
    // | <----------    <----------
    // |            /\ |           /\ .
    // | edgey       | |           |
    // |             | |           |
    // \/            | \/          |
    
    /* gather all rows */
    size_t y=0;
    for (; y<height; y++)
    {
      /* here edgey points from top/left vertex downwards */
      unsigned int edgex = edgey;

      /* gather all columns */
      size_t x=0;
      for (; x<width; x++)
      {
        /* here edgex points from left vertex of row downwards */
        positions[y*(width+1)+x] = vertices[indices[edgex]];

        /* prev -> prev -> opposite moves to the next column (unless we reach the right end) */
        edgex = rtcGetGeometryPreviousHalfEdge(geom,edgex);
        if (x+1 < width) {
          edgex = rtcGetGeometryPreviousHalfEdge(geom,edgex);
          edgex = rtcGetGeometryOppositeHalfEdge(geom,0,edgex);
        }
      }
      /* load rightmost vertex */
      positions[y*(width+1)+x] = vertices[indices[edgex]];

      /* next -> opposite -> next moves to next row (unless we reach the bottom) */
      edgey = rtcGetGeometryNextHalfEdge(geom,edgey);
      if (y+1 < height) {
        edgey = rtcGetGeometryOppositeHalfEdge(geom,0,edgey);
        edgey = rtcGetGeometryNextHalfEdge(geom,edgey);
      }
    }

    /* special treatment for last row, edgy points from the bottom/left vertex to the right */
    unsigned int edgex = edgey;
    for (size_t x=0; x<width; x++)
    {
      positions[y*(width+1)+x] = vertices[indices[edgex]];

      /* next -> opposite -> next moves to the next column (unless we reach the right end) */
      edgex = rtcGetGeometryNextHalfEdge(geom,edgex);
      if (x+1 < width) {
        edgex = rtcGetGeometryOppositeHalfEdge(geom,0,edgex);
        edgex = rtcGetGeometryNextHalfEdge(geom,edgex);
      }
    }
    /* load rightmost vertex */
    positions[height*(width+1)+width] = vertices[indices[edgex]];
  }