[OSM-talk] Funding of three infrastructure projects : Nominatim, osm2pgsql, Potlatch 2

Matthew Woehlke mwoehlke.floss at gmail.com
Tue Aug 4 14:26:17 UTC 2020

On 04/08/2020 08.10, Martin Koppenhoefer wrote:
> On 4. Aug 2020, at 13:58, Matthew Woehlke wrote:
>> but I would practically *kill* for JOSM to have FreeCAD's suite of sketch constraints ;-).
> you’re aware that there are sketch constraints for configurable
> angles (90, 60, 45 etc) and projection snaps? Hit 2 times „a“ (angle
> display becomes green)
Yes. They're better than nothing, but nowhere near what I'm talking 
about. As an example, consider the attached simple FreeCAD sketch which 
is roughly representative of some buildings I've mapped recently. The 
dome in front is centered (segments on either side constrained to be 
equal). The "wings" in back are symmetrical.

It's *possible* to do this sort of thing in JOSM with a lot of care and 
by building part of the geometry, then constructing a bunch of "scratch" 
geometry in order to construct a symmetry line, then doing a copy, paste 
in place, mirror, reverse, stitch the parts together... but God help you 
if you make a mistake and have to start over.

In FreeCAD, you just slap on some equality constraints, angle 
constraints, parallel constraints, etc. and then you can *move* any of 
the nodes and everything else will update to preserve the applied 
constraints. (The one things it's missing that would be helpful is a 
*colinear* constraint; you have to simulate that with parallel and 
coincident constraints using "construction" lines; those are the blue 
ones. A colinear constraint could eliminate the need for those 
construction lines.) This is the major difference, though. In JOSM, 
constraints only apply when you initially draw something, so if you get 
it wrong, you have to start over. In FreeCAD, they're a dynamic system; 
if you get it wrong, just nudge it and the whole thing updates *while 
preserving your constraints*.

Oh, and *arcs*. The ability to define a segment that should be a perfect 
arc, and optionally make it tangent or perpendicular to its neighbors, 
would be a major boon. Again, I can fake it with a bunch of scratch 
construction, but if it's wrong, I have to start over and hope my next 
guess is better. In FreeCAD, just drag the end points until it looks right.

Then there are distance constraints, which would be incredibly useful if 
you're mapping something with known dimensions.

Seriously, give FreeCAD a spin. It's pretty awesome for this sort of 
relatively simple 2D stuff. Also look at some of the buildings I've done 
recently; the symmetrical ones don't just *look* symmetrical, they *are* 
symmetrical (within the limits of JOSM's abilities). I've also done a 
lot of stuff like roads that are perfectly centered in between parking 
spaces, groups of aligned buildings that are *actually* aligned, and 
whatnot. It's do-able, but it would be *soooo* much easier with 
FreeCAD-style constraints.

Obviously, this would all almost surely be a temporary mode (maybe it 
persists as long as JOSM is open, but isn't uploaded), but since you 
usually draw once, that would be fine. (Bonus points if JOSM could 
automatically recreate constraints for ways that don't have any. It 
shouldn't be hard to guess equality, perpendicular and colinear 
constraints, at least.)

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