@Override
    public void setLodLevel(int lod) {
        if (mesh.getNumLodLevels() == 0) {
            throw new IllegalStateException("LOD levels are not set on this mesh");
        }

        if (lod < 0 || lod >= mesh.getNumLodLevels()) {
            throw new IllegalArgumentException("LOD level is out of range: " + lod);
        }

        lodLevel = lod;

        if (isGrouped()) {
            groupNode.onMeshChange(this);
        }
    }
Sets the LOD level to use when rendering the mesh of this geometry.
Level 0 indicates that the default index buffer should be used,
levels [1, LodLevels + 1] represent the levels set on the mesh
with {@link Mesh#setLodLevels(com.jme3.scene.VertexBuffer[]) }.

@param lod The lod level to set
jme3-core/src/main/java/com/jme3/scene/Geometry.java