I hope there's something easy that I'm missing...
 
The 2DArcReplacer does not appear to allow the simple 3-point notation for 
circular arcs.  That's too bad; it's what we're most likely to get out of text 
representations of arcs from databases like as Oracle, PostGIS, and SDF.
 
I can see a few options:
 
1. If you don't need to maintain the exact three-point arc, then you can
  - 2DPointReplacer with x1, y1
  - 2DPointAdder with x2, y2
  - 2DPointAdder with x3, y3
  - ArcEstimator
 
2. Figure out how to create a GML document that includes a 3-point arc and can 
be read by the GMLFeatureReplacer.  Use a Concatenator to wrap that GML around 
your coordinate list (they likely go inside a <gml:posList /> element).
 
3. Do some really painful math to infer the parameters that FME uses in the 
2DArcReplacer.  I may not understand their notation, but I think... 
  - maybe you can ignore rotation
  - the radii/axis should be the same because you're working with a circular arc
  - http://mathforum.org/library/drmath/view/54323.html can give you the center 
point
  - the radius is the distance between the centrepoint and any other point 
(Pythagoras)
  - start angle should be should be calculable as the angle counter-clockwise 
between a vertical line from the midpoint and a line between the midpoint and 
x1, y1.
  - I think the sweep angle should be the difference in degrees 
counter-clockwise between the start angle and a similar angle calculated for 
x3, y3.
 
4. Petition Safe to expand its arc support by adding different arc notation 
styles to Creator and (2D|3D)ArcReplacer.
 
Good Luck!
 
Jason

________________________________

From: [email protected] on behalf of mhabarta
Sent: Fri 2007-01-19 5:37 PM
To: [email protected]
Subject: [fme] Creating an Arc from values in coordinates and attributes



Hallo FMEers

I am kind of locked in the following problem:

I have features with 1 coordinate/position which is the center for the
supposed arc, and I have the positions for start/end point of the arc
in attributes at the feature.

How can I "warp" these features into ARCs ?

GeometryReplacer doesn't know attributes, and XMLGeometryReplacer
seems not usable too ?

Thanks for any hint
Michael




For insights into what's up at Safe Software and what's on the development 
horizon, visit Safe's blog at spatial-etl.blogspot.com.

Safe Software has also made slides available that outline enhancements planned 
for FME 2007. The slides are from the "Road Ahead" presentation given on Day 2 
of the FME Worldwide Users Conference. To view these slides, visit 
www.safe.com/2006uc.

 
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