VS:OffsetPoly
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Description
Returns a poly, or the handle to a group of polys, which is the result of offsetting the input handle.
The input handle can be a:
- line
- arc or circle
- rectangle
- rounded rectangle
- ellipse
- polygon (open or closed)
- polyline (open or closed)
- group containing one or more of these objects
When offsetting a line, a positive offsetDistance will offset to the left, looking from the start to the end of the line.
When offsetting an arc, a positive offsetDistance will create a polyline approximation of an arc of a larger radius.
When offsetting any closed shape, a positive offsetDistance will offset to the outside.
When offsetting an open polygon or polyline, the direction of the offset will depend on the overall sense of the poly. From start to end, if the poly turns right more than left, the offset will be to the left, if offsetDistance is positive.
Removes self-intersecting segments from the result, making it useful for offsetting when interference is an issue.
Returns the handle to the newly created polyline, or to a group if the result contains more than one polyline. The return will be a group if numberOfOffsets is greater than 1, or if offsetDistance is negative, and the removal of self-intersecting segments resulted in multiple objects.
If consolidateVertices is TRUE, nearly colinear straight segments will be consolidated into a single straight segment, and nearly concentric arc segments will be consolidated into a single arc (approximated by polygon vertices).
If sharpCorners is FALSE, when offsetting a convex intersection, an arc will be created, centered at the intersection, to transition from one segment to the next. If it is TRUE, no arc will be inserted, and the adjacent offset segments will be extended to their intersection. If no intersection exists, such as when offsetting a line, and the adjacent offset segments are parallel, arcs will be introduced to transition between the segments.
ConversionRes is the "2D Conversion Resolution" that will be used to polygonalize the polyline prior to offsetting. It should be possible to set this to a pretty low number if you're also using consolidateVertices, since this will replace line segments with arcs where possible.
ConsolidationTolerance is total allowable chordal variance between line segments and the arc, if consolidateVertices is TRUE.
FUNCTION OffsetPoly(
h :HANDLE;
offsetDistance :REAL;
numberOfOffsets :INTEGER;
consolidateVertices :BOOLEAN;
sharpCorners :BOOLEAN;
conversionRes :INTEGER;
consolidationTolerance :REAL) :HANDLE;
def vs.OffsetPoly(h, offsetDistance, numberOfOffsets, consolidateVertices, sharpCorners, conversionRes, consolidationTolerance):
return HANDLE
Parameters
h HANDLE offsetDistance REAL numberOfOffsets INTEGER consolidateVertices BOOLEAN sharpCorners BOOLEAN conversionRes INTEGER consolidationTolerance REAL
Remarks
Orso (2010/03/19) This fails at least on metric units whenever the offset is less than 1. It makes a copy in place instead. For example:
- Units meter, offset 1m > succeeds
- Units meter, offset 0.9m > fails
- Units centimeter, offset 1cm > succeeds
- Units centimeter, offset 0.9cm > fails
Thank you Petri for pointing this out to me. :)
Example
PROCEDURE Example;
{Offsets the selected object.}
VAR
h :HANDLE;
dist :REAL;
numberOfOffsets :INTEGER;
consolidateVertices :BOOLEAN;
sharpCorners :BOOLEAN;
conversionRes: INTEGER;
consolidationTolerance: REAL;
BEGIN
dist := 100;
numberOfOffsets := 1;
consolidateVertices := false;
sharpCorners := false;
conversionRes := 16;
consolidationTolerance := 1;
h := OffsetPoly(FSActLayer, dist, numberOfOffsets, consolidateVertices, sharpCorners, conversionRes, consolidationTolerance);
END;
RUN(Example);
Version
Availability: from All Versions
This is drop-in function.