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Stefano,
last night I did some DevCad work on my new-to-be-built CNC hot wire machine, and of course I made use of the deferred tangent snap function. This made me think over our yesterdays exchange of thoughts, and I disagree with the yesterday's conclusion.
Of course it became clear, that deferred tangent snap is not going to be applicable to polylines. But the use along with construction lines still makes me wondering.
Background: In the 1970ies I learned the basics of technical drawing and construction. Oldschool with A0 size drawing board, ruler, pencil and ink-pen on transparent paper. The basic working scheme was always the same: starting with drawing overlong pencil lines, and then finding and drawing all required intersections, perpendiculars, angled lines, parallels and so forth, again with overlong pencil lines. When all preparation work was finished that way, then the final lines were drawn with ink-pen, on the pencil lines and from intersection to intersection. Finally, the remainders of the pencil lines were erased.
One of the charming aspects of DevCad is, that it pretty well resembles such oldschool drawing scheme on the computer screen. Snap points allow me to correctly place my imaginary digital ruler for drawing my overlong pencil help lines, now being the on screen construction lines. By doing so I find all my relevant intersections and so forth. And once I have identified them, I do the real job: Drawing a part with (poly)lines, arcs and circles and so forth.
This is intuitive, and works for nearly everyhing, except finding a tangent on two curved items. The present workaround is:
QUOTE (duroneee @ 22/11/2017, 14:04) The right approach is to use a temporay line, as you do, I think.
Yes this is the way I do. And yes, it works. But no, this is not the right approach. Its a break in design logic. I abuse a "real" line for the purpose of a construction line. This is counter-intuitive. And in practice it has some drawbacks. In complex structures it is then hard to distinguish between helping lines and real body lines. And basically this is the reason, why helping lines or construction lines exist.
QUOTE (duroneee @ 22/11/2017, 14:04) About construction lines, that doesn't help a lot I think, as construction lines are usually for long term drawing and the conctruction line itself is infinite, so would not help you a lot to get the right tangent points.
This is a further point where I disagree. Using an infinite construction line would be perfect for the purpose in question. It would not only allow for identifying the the two corresponding tangent points. I would also allow for extrapolating in any direction along the line, finding parallels, or perpendiculars on whatever point along the course of the construction line. And it would be easy to distinguish from intended body lines, and can be deleted without messing up with the body lines. And by the way, I don't see any reason why construction lines should be limited to long term drawing. I often use them on a short term basis for finding an intersection or whatever else is instantly required.
In short summary: The discussed deferred tangent snap issue is no show stopper, and using a single line does work. But it is illogical from the viewpoint of design approach. DevCad's construction lines are so valuable and powerfull. Nearly all snap function work well with the construction lines, contributing to their value. So why not giving them the deferred tangent snap capability? This capability is already present in DevCad. It's not really a new feature. In my eyes its just a question of logic and availability.
But again, its not a showstopper, and there is no urgency behind it. Take it as a feature request for introduction, whenever your schedule does allow for.
Cheers,
Stefan.
Edited by Haegar - 23/11/2017, 11:48
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