There are also internal options
used only by sketch and not
passed on to PSTricks.  These are summarized in the following
table. 
   
| Key | Possible values | Description | 
|---|---|---|
| cull | true,false | Turn culling of backfaces on and off respectively for this object. 
The default value is true. | 
| lay | over,in,under | Force this object to be underoroverall other objects in the depth sort
order created by the hidden surface algorithm.  The default valueoverguarantees that output due to thespecialwill be
visible. | 
| split | true,false | Turn splitting of sweep-generated body polygons
on and off respectively. See Sweeps.  The default value truecauses “warped” polygons to be split into triangles, which avoids
mistakes by the hidden surface algorithm. | 
(x1,y1,z1)(x2,y2,z2)...
A sequence of one or more points makes a point list, a feature common to all drawables. Each of the point components is a scalar arithmetic expression. Any point may have the z-component omitted; it will default to z=0.