TYPE: SOP
TITLE: Add SOP

The Add operation can both create new points and polygons on its own, or it can
be used to add points and polygons to an existing source.

If an Input Source is specified, this operation adds points to the ones
inherited from its source, and creates polygons out of both existing and newly
generated points. If Add's input is not connected, it can create polygons only
with the points generated in the Points tab.

Parameters
Points
    Overview - The three leftmost input fields represent the X,Y and Z
	       coordinates of the point. The last input field represents the
	       spline weight of the point. If the point is later used to create
	       a spline (NURBS or Bezier) primitive, the weight will influence
	       the shape of the primitive and may cause that primitive to
	       become rational. Polygons and metaballs are not affected by this
	       weight.
	       
	       X, Y, Z, and W can be constants (numbers) or variables.

    Delete Geometry But Keep the Points - This will destroy all the
	       polygons, NURBs, and other primitives, leaving only the
	       points intact.
    
Polygons: By Pattern
    Overview - Create a fixed number of polygons by specifying a point
               pattern for each polygon Enter connection lists here to
               create polygons.

               ~c(
	       {from}-{to}[:{every}][,{of}]
               eg1: 1 2 3 4
               eg2: 1 3-15 16 8
               eg3: 1-234 820-410 235-409
               eg4: 0-15:2
               eg5: 0-15:2,3
	       ~c)

Polygons: By Group
    Overview - Create as many polygons as determined by the group field
               and by the grouping/skipping rules
    Group    - Subset of points to be connected
    Add      - Optionally join subgroups of points
    N        - Increment to use for subgroup joining.      /inc
    Attribute - If group by attribute is specified, this attribute
		will be used to determine how to connect the polygons
		within the group.  Points with the same attribute
		value will be connected together.  The connection
		order will respect the point order of the group.

    Remove Unused Points - Keep only the connected points

Local Variables
    N                         - Index of the last point in the geometry.
    CEX, CEY, CEZ             - The centroid of the input
    XMIN, XMAX                - The X extents of the bounding box of the input
    YMIN, YMAX                - The Y extents of the bounding box of the input
    ZMIN, ZMAX                - The Z extents of the bounding box of the input
    SIZEX, SIZEY, SIZEZ       - The size of the bounding box of the input
