[GRASS-dev] proper v.parallel behavior on strange input

[Росен Матев]

I'm trying to say that I can't figure out what should loopless lines
look like. The criteria currently used in clean_parallel() is bad,
cause it removes loops, for which common sense says they shouldn't be
removed. (See my triangular loop example with parallel line on the
right. Currently clean_parallel() removes the formed loop). I doubt
that there is sensible criteria for removal of loops. That's why I'll
remove the "-l" option (for now and probably forever) and then I'll
work on type B/C lines.

Rosen

On Thu, Jun 19, 2008 at 3:25 PM, Wolf Bergenheim
<wolf+grass at bergenheim.net> wrote:
> On 18.06.2008 22:24, Росен Матев wrote:
>>
>> Hi,
>>
>> I propose that I cancel development of "clean_parallel()" (the
>> function which removes loops), cause its proper behavior is not
>> determined now (and it might not be possible to determine it).
>> Instead, I'll start making function which generates "type B" lines,
>> which will be more useful in buffer generation. What do you think
>> about it?
>
> I still think that both A and B have merit, depending on what you want to do
> with the parallel lines. If it is meant to mark the the side of the road
> that gets cleared for installation of say phone wires, and all lines go in
> the direction of the traffic, then A is the way to go. If you want to make
> buffers then B, no sorry C (B with holes), is the correct way to go. Once
> you are dine with making parallel lines according to B you need to go
> through the original line again to find loops and for those loops punch
> holes.
>
> As for the loop removal, ell if you can produce a function that can produce
> loopless parallel lines, then by all means drop clean_parallel(). Note that
> the the previous problem case also needs to work ;). I'll also ponder on the
> parallel line algorithm.
>
> Another way to go would be to emulate a CNC machine and place a circular
> "tool" on top of the line and calculate a tangent at each corner to connect
> two balls on the left and right side. But that might actually be harder then
> going via parallel lines. I'm not sure. But it would allow for all kinds of
> interesting buffer shapes.
>
> --Wolf
>
> --
>
> <:3 )---- Wolf Bergenheim ----( 8:>
>
>