Re: [OSM-dev] looking for some spline code to adapt

2017-07-02 Thread Martin Koppenhoefer 


sent from a phone

> On 2. Jul 2017, at 15:15, Christoph Hormann  wrote:
> 
> The problem is that in OSM we do not record any supplemental information 
> on ways regarding if the corners at the nodes are actual corners or if 
> they are just approximations for a smooth form of some sort - what you 
> would usually do with a kind of tension parameter.


at least we don't do it on a bigger scale, there are very few examples where 
someone has done it: https://taginfo.openstreetmap.org/keys/bezier

or has proposed to do it:
https://wiki.openstreetmap.org/wiki/Relations/Proposed/Curvature

Maybe we should push for a common solution to add this kind of information?

Cheers,
Martin ___
dev mailing list
dev@openstreetmap.org
https://lists.openstreetmap.org/listinfo/dev

Re: [OSM-dev] looking for some spline code to adapt

2017-07-02 Thread Christoph Hormann 
On Sunday 02 July 2017, Rich Morin wrote:
> I'm generating sets of tactile maps for a blind friend, as follows:
>
>   OSM export files -(Ruby)-> PostScript -(lpr)-> swell paper
>
> I'm using straight lines for the roads, using the PostScript moveto
> and lineto operators.  However, I'd like to use the curveto operator:
>
>   x1 y1 x2 y2 x3 y3 curveto -
>
>   This operator draws a curve from the current point to the point
> (x3, y3) using points (x1, y1) and (x2, y2) as control points. The
> curve is a Bézier cubic curve. In such a curve, the tangent of the
> curve at the current point will be a line segment running from the
> current point to (x1, y1) and the tangent at (x3, y3) is the line
> running from (x3, y3) to (x2, y2).
>
> [...]

You can certainly do so but you need to expect that your results are 
largely wrong.

The problem is that in OSM we do not record any supplemental information 
on ways regarding if the corners at the nodes are actual corners or if 
they are just approximations for a smooth form of some sort - what you 
would usually do with a kind of tension parameter.  Neither can you 
rely on the fact that when two roads connect this is not a smooth 
transit.  It is not even defined if when a way approximates a smooth 
form the nodes of the way are supposed to be on the curve or if they 
should be placed so the average distance of the way to the curve is 
minimized.

-- 
Christoph Hormann
http://www.imagico.de/

___
dev mailing list
dev@openstreetmap.org
https://lists.openstreetmap.org/listinfo/dev

[OSM-dev] looking for some spline code to adapt

2017-07-02 Thread Rich Morin 
I'm generating sets of tactile maps for a blind friend, as follows:

  OSM export files -(Ruby)-> PostScript -(lpr)-> swell paper

I'm using straight lines for the roads, using the PostScript moveto
and lineto operators.  However, I'd like to use the curveto operator:

  x1 y1 x2 y2 x3 y3 curveto -

  This operator draws a curve from the current point to the point (x3, y3)
  using points (x1, y1) and (x2, y2) as control points. The curve is a
  Bézier cubic curve. In such a curve, the tangent of the curve at the
  current point will be a line segment running from the current point to
  (x1, y1) and the tangent at (x3, y3) is the line running from (x3, y3)
  to (x2, y2).

  -- http://www.tailrecursive.org/postscript/operators.html

I'm not sure what the best starting point would be for this.  I found this
Perl code, but it seems a bit dated:

  http://wiki.openstreetmap.org/wiki/Osmarender/BezierCurves

Clues, comments, and suggestions?

-r

 -- 
http://www.cfcl.com/rdm   Rich Morin   r...@cfcl.com
http://www.cfcl.com/rdm/resumeSan Bruno, CA, USA   +1 650-873-7841

Software system design, development, and documentation



___
dev mailing list
dev@openstreetmap.org
https://lists.openstreetmap.org/listinfo/dev