******************************************************************************
** Global commands:
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obj name
    Begin describing an object with the specified name.
    Object commands should follow.
    Object description lasts until the next global command.
    Entering an object definition doesn't "empty" the object - existing
    primitives aren't deleted (so new primitives will be appended).
    To redefine an object, use the "empty" command.

cam eyex eyey eyez centerx centery centerz [upx upy upz]
    Move camera to specified eye position, looking at specified center point.
    The up vector is a vector pointing upwards from the camera (specifying
    camera orientation).
    The up vector can be omitted; in this case, projector tries to calculate
    a reasonable up vector, so that the plane defined by the (eye-center)
    vector and the up vector contains the Z axis, and the up vector points
    towards positive Z.

fov number
    Set field of view (in degrees). Default 90.

render
    Render frame.

******************************************************************************
** Object commands:
******************************************************************************

Points for primitives can be described in two ways:
    x y z - three numbers; add new vertex to object, use that vertex
    :n    - use existing vertex number N (vertices are numbered from 0)

show
    Show object (default).

hide
    Hide object (default).

empty
    Delete all primitives.

pos x y z
    Set object position.

mat ux uy uz vx vy vz wx wy wz
    Set transformation matrix.

color color
    Set default color for primitives.
    Default black, but this isn't reset with entering new object definitions,
    so it has a global effect.
    Uses the same color definition syntax as animator.

lines point1 point2 ...
    Add a new primitive with the current color, that draws a line of multiple
    connected segments.

verts x1 y1 z1 [x2 y2 z2 ...]
    Add new vertices to the object.