#### 7.2.85 ND-axes

`(ND-axes CAMID [CLUSTERNAME [Xindex Yindex Zindex [Windex]]])`
  In our model for N-D viewing (enabled by (dimension)), objects in N-space are viewed by N-dimensional camera clusters. Each real camera window belongs to some cluster, and shows & manipulates a 3-D axis-aligned projected subspace of the N-space seen by its cluster. Moving one camera in a cluster affects its siblings.

  The ND-axes command configures all this. It specifies a camera's cluster membership, and the set of N-space axes which become the 3-D camera's X, Y, and Z axes. Axes are specified by their indices, from 1 to N for an N-dimensional space. Cluster CLUSTERNAME is implicitly created if not previously known.

  In principle it is possible to map the homogeneous component of a conformal 4 point to some other index; this would be done by specifying 0 for one of `Xindex`, `Yindex` or `Zindex` and giving `Windex` some positive value. This is probably not useful because Geomview does not support non-Euclidean geometries for in higher dimensions.

  To read a camera's configuration, use `(echo (ND-axes CAMID))`. The return value is an array of 4 integers, the last one should 0.