PFAS(3g) — Subroutines

Name

PFAS − Defines a 2D fill area set primitive.

Operating States: PHOP, ∗, STOP, ∗
PHIGS standard function
Creates a structure element

Syntax

PFAS (NPL, IXA, PXA, PYA)

Argument     Data Type        Access    Description
---------------------------------------------------------------------------
N            Integer          Read      Number of fill areas
IXA(NPL)     Array of         Read      Array of end indexes for the point
             integers                   lists.
PXA(∗),      Array of reals   Read      Coordinates of the points in each
PYA(∗)                                  fill area, in modeling coordinates.
                                        The points are ordered so the list
                                        of points for the second fill area
                                        follows the list of points for the
                                        first, and so on to the nth fill
                                        area.
---------------------------------------------------------------------------

Description

PFAS creates a structure element that uses a list of points to define a two-dimensional fill area set primitive.

Depending on the current edit mode, this function either inserts the new structure element directly after the element indicated by the element pointer or replaces the element indicated by the pointer. The pointer then points to the new fill area set element.

The PFAS function specifies the two-dimensional (x and y) form of the fill area set primitive. The default z-coordinate of the primitive is 0. The function, along with its attributes, draws a complex polygon. You can define both the interior and exterior (edge) attributes of the polygon.

A call to this function has the following effects during structure traversal:

•Digital PHIGS generates a set of polygonal areas made up of a collection of subareas.

•Digital PHIGS closes any unclosed polygon (subarea), implicitly.

•Digital PHIGS binds the current values of the fill area set attributes, as defined in the PHIGS traversal state list, to the fill area set primitive.

Attribute values control whether or not edges appear in the display.

The interior of a fill area set primitive is defined as follows:

•For a specified point, a straight line is created starting at that point and continuing on to infinity.

•If the number of intersections between the straight line and the fill area boundary is odd, the point is within the fill area.

•If the number of intersections between the straight line and the fill area boundary is even, the point is outside the fill area.

•If the straight line passes through a fill area vertex tangentially, the intersection count is not affected.

If Digital PHIGS is in immediate mode, it performs this function immediately, but the function does not create a structure element. The following must be true, or Digital PHIGS may generate an error:

•NPL>=1

•PXA and PYA are dimensioned by at least IXA(NPL)

•IXA(1)>=3

•IXA(i+1) -- IXA(i)>=3, for i=1 to NPL--1, when NPL>=2 (the ith point list is at least 3 points)

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PFAS(3g) — Subroutines

Name

Syntax

Description

See Also