##### 3.1.5.4 Internal options

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 `under` or `over` all other objects in the depth sort order created by the hidden surface algorithm. The default value `over` guarantees that output due to the `special` will be visible.
`split` | `true`, `false` | Turn splitting of sweep-generated body polygons on and off respectively. See Sweeps. The default value `true` causes “warped” polygons to be split into triangles, which avoids mistakes by the hidden surface algorithm.

#### 3.1.6 Point lists

Syntax:

         (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.