Re: [OSM-dev] curves
On Fri, Jan 04, 2008 at 03:02:15PM +, Artem Pavlenko wrote: What I could see working is something like this : we define a standard interpolation method that turns a set of point into a sucession of bezier curves. (for an example see http://www.antigrain.com/research/bezier_interpolation/index.html) I understand you have already implemented another on the fly algorithm in mapnik, we could use that as well. mapnik is using AGG for rendering, so yes, this is exactly what I'm doing :) Excellent. I'll try to get this working in merkaartor sometime next week then. See what kind of experiments we can come up with. Do you think we need the 'smoothness factor?' I'd like to try with fixing it to '1' for now. The less complicated we make it, the easier it will be to convince people and tool writers to support it? Or an opposite, people will be adding too many vertices in editors that are lacking support for bezier interpolation.. But then hopefully they'll also not be setting smooth=yes? cu bart ___ dev mailing list dev@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/dev
Re: [OSM-dev] curves
Frederik Ramm wrote: Sent: 03 January 2008 4:53 PM To: Robert (Jamie) Munro Cc: dev Openstreetmap Subject: Re: [OSM-dev] curves Hi, What people think about explicitly supporting curves as a part of geometry model? This way we can model the world better. When I suggested this before, someone said it was patented, possibly by either NavTeq or TeleAtlas, Navteq seem to have a patent on using Bezier curves for road network representation or something. It was on the lists here. Try this for size: http://www.freepatentsonline.com/7007011.html Cheers Andy I also find the idea very tempting, however one has to bear in mind that some things could then become very difficult. For example, computing the combined length of all motorways is trivial today, and will probably require specialist tools if we go Bezier. Equally, finding intersections and the like (think Validator plugin) - probably a computational nightmare if Beziers are involved. Will the built-in PostGIS stuff (give me everything that intersects with this rectangle) work out-of-the box with Beziers? Bye Frederik ___ dev mailing list dev@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/dev ___ dev mailing list dev@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/dev
Re: [OSM-dev] curves
On 3 Jan 2008, at 16:53, Frederik Ramm wrote: Hi, What people think about explicitly supporting curves as a part of geometry model? This way we can model the world better. When I suggested this before, someone said it was patented, possibly by either NavTeq or TeleAtlas, Navteq seem to have a patent on using Bezier curves for road network representation or something. It was on the lists here. It must be more then just representation of road network. There are so much prior art - CAD and even some 70s GIS could do bezier curves. I also find the idea very tempting, however one has to bear in mind that some things could then become very difficult. For example, computing the combined length of all motorways is trivial today, and will probably require specialist tools if we go Bezier. Equally, finding intersections and the like (think Validator plugin) - probably a computational nightmare if Beziers are involved. Yes, true. One way to deal with beziers is to convert them to polylines (easy) when computing intersection , length etc. Will the built-in PostGIS stuff (give me everything that intersects with this rectangle) work out-of-the box with Beziers? No. PostGIS doesn't support beziers. But spatial queries like 'intersect', 'within' are usually implemented as two step process: 1. check if geometry bbox intersects query bbox 2. refine query based on results from (1). Bye Frederik Cheers Artem ___ dev mailing list dev@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/dev
