Let me try that ....
- start parameter is always 0
- end parameter is always the arc length of the curve
So for a single curve segment it seems understandable (not sure what it
is used for .... is this really in the ISO spec?)
For the next case it seems to be when several curve segments are used
together (maybe they form a Ring?), in which case they seem to measure
the "arc length" to the start of the very first curve segment.
0 5
|-----| single segement "5" long
So the javadocs are saying we need to "measure the curve length from the
first curve":
0 5
|-----|---|
5 8
Rather than this:
0 5
|-----|---|
0 3
I can only assume these numbers are important for making operations
efficient ... seems very strange to me.
Jody
> We are also a bit confused about what the "startParam" field required
> for the LineSegmentImpl constructor is for.
> public LineSegmentImpl(DirectPosition one, DirectPosition two,
> double startParam) {
> this( new PointArrayImpl( one, two), startParam
> ); }
>
> It inherits back from CurveSegmentImpl and CurveSegment which has
> these comments about startparam:
>
> * The start and end parameter of a Curve are always 0 and the arc
> length of
> * the curve respectively. For CurveSegments within a Curve, the
> start and
> * end parameters of the CurveSegment are equal to those of the
> Curve where
> * this segment begins and ends in the Segmentation association, so
> that the
> * startParam of any segment (except the first) is equal to the
> endParam of
> * the previous segment. If a GenericCurve is used for other
> purposes, there
> * shall be a restriction that the two parameters must differ by
> the arc
> * length of the GenericCurve.
>
> I guess we're just not sure exactly what this parameter is used for
> and if it is even necessary.
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