kicad-developers team mailing list archive

[jp charras <jp.charras@xxxxxxxxxx>]

Le 19/09/2014 00:54, Tomasz Wlostowski a écrit :
> On 18.09.2014 23:16, Wayne Stambaugh wrote:
>> On 9/18/2014 4:42 PM, Cirilo Bernardo wrote:
>>> ----- Original Message -----
>>>
>>>> From: Tomasz Wlostowski <tomasz.wlostowski@xxxxxxx>
>>>> To: Kicad Developers <kicad-developers@xxxxxxxxxxxxxxxxxxx>
>>>> Cc:
>>>> Sent: Friday, September 19, 2014 2:04 AM
>>>> Subject: [Kicad-developers] P&S plans for the near future
>>>>
>>> [snip]
>>>> I'd also like to add support for arcs on copper layers (for efficient
>>>> representation of miters/meanders). Contrary to the current graphical
>>>> arc object, I'd propose to approximate them using line segments (and
>>>> store as such approximations) so that there's no need to add full arc
>>>> support (for plotter/DRC/etc). What do you think?
>>>>
>>>
>>>
>>> Hi Tom,
>>>
>>>   For the arcs I think ideally we should use real arcs; if line segments
>>> are used then we need to be able to specify some dimensional constraint
>>> so that the arcs appear smooth. It's only a wishlist item though since
>>> the DRC around arcs would be a challenge. One potential issue of using
>>> line segments is that a design can end up with very many segments in a
>>> single arc and these segments can be accidentally dragged or deleted.
>>>
>>> - Cirilo
>>>
>>
>> At some point we should consider supporting arcs but from what I
>> understand implementing arc support in gerber files is very difficult.
>> Although I haven't really looked at it.  I'm just going by what I have
>> heard discussed in the past.
> 
> Hi again,
> 
> That's why I proposed to use a piecewise approximation instead of ideal
> arcs (in the case of Gerber output, it will produce a number of segments
> instead of a real arc).
> 
> Tom

Tom, Orson,

Your planned improvements are very great.

About arc support for tracks, using a piecewise approximation is a
reasonable idea.
Anyway, in all cases (drc, filling zones ...) arcs will be converted to
segments in calculations.
Using true arc in plotting/drawing functions, and segments in
calculations, will create issues, and surely a lot of bug reports.

True arcs are tricky to handle.
The first issue is the fact the Y axis in Pcbnew is reversed. This
creates a lot of problems in complex calculations.

But true arc support is not easy, mainly after they are created and
connected to tracks, when you are are editing these tracks (dragging,
moving, changing angle between tracks connected to the arc...) or these
arcs.

At least, using segment approximations avoid to write a lot of code to
handle true arcs (and does not change the .kicad_pcb files, although
this is not a major issue).
(For representation of miters/meanders, the current code should be enough).

Using true arcs later, if we see issues with segment approximations, is
always possible.


-- 
Jean-Pierre CHARRAS