if (is3D) {
space = new OctreeCellSpace(new Anchor(-1, -1, -1), new Anchor(1,
1, 1));
} else {
space = new QuadtreeCellSpace(new Anchor(-1, -1, -0.01f),
new Anchor(1, 1, 0.01f));
}
this.nodes = new ParticleBox(nodesPerCell, space,
new GraphCellData());