QCAD.org Forum

Objective: Draw a line with 75° tangential to a circle

Is there a tool that can do that?

My steps:
1) draw circle with Center, Point (CI)
2) draw Line from Angle (LA) with 75°
3) choose Tangential (SB) and click on circle

That did not work.

NB: Of course I know how to "construct" a tangent, which I did.

I am using the latest 64 bit Linux version.

Yep ..... the mysterious Tangential snap ...

First of all - I see it like you and I think the behavior of this tool is far away from the user expectation what this tool should do. I'm sure - mathematically correct and ...
... the already postet Bugreport is market as expected behavior:

http://www.ribbonsoft.com/bugtracker/in ... sk_id=1335

However - I expect from this tool that it will snap to all tangential points on a circle/ arc etc regardless the Relative Zero location. In your case would it show two location and I have to decide to which one it has to snap.

I would use the same tool chain like you
1) draw circle with Center, Point (CI)
2) draw Line from Angle (LA) with 75°
3) choose Tangential (SB) and click on circle

... same for move / copy etc etc

I think it is an important tool to place (what ever) tangential to an existing entity but right no it is useless to me and I have to go always the long road ...

....it looks like I'm not alone.

The tangential snap is useful for one situation only: when drawing a line from a point tangential to a circle or arc. The tangential snap (just like all other snaps) are completely unaware of what you are currently drawing, moving, positioning, etc.

Andrew, could the tangential snap be made to work with angled lines?

It works with a line from a point to a circle, because the point tells it under which angle the line passes the circle by. If the angle is given, no point should be needed. Or am I completely wrong?

May I ask to put an additional thought into this?

I would also like to have the possibility to move/copy single entities, Polygons, Blocks, Selections tangential to an circle, arc, ellipse just with a snap. That is something what I would consider as a daily task.

Example to move a rectangle under an angle with a given reference to a circle:

caigner wrote:Andrew, could the tangential snap be made to work with angled lines?

The snaps are (and arguably should be) unaware of what tool you are using. A snap should not behave differently for one tool than for another.

Imagine implementing a relationship between N tools and M snaps. That's potentially NxM different behaviours.

Husky wrote:I would also like to have the possibility to move/copy single entities, Polygons, Blocks, Selections tangential to an circle, arc, ellipse just with a snap. That is something what I would consider as a daily task.

Thanks for your input.

How would QCAD know to which of the selected lines or other entities the tangential relationship refers to? The one closest to the reference point? There might be N entities going through the reference point at various angles (two in your example).

Thanks for your interest .... I was used to this in older CAD Systems.

It should work like this task/tool chain:

Select what needs to be moved/copy (single entities, Polygons, Blocks etc.),
launch move/copy tool,
Choose the reference point as usual for this tool - in this case intersection "1",
Launch "a snap to tangent" tool / tell QCAD with a mouse click which entity is meant to be used for the angle (2),
hoover over the target - in this case the bigger circle which should offer then two possible position,
Confirm with the mouse the right one - done.
This could also work as a solution for caigner's request ...

Thanks. Any idea how such a system would behave in this case (reference point being the intersection of the line bundle)?

Sorry - my post wasn't complete. Revision with mouse click (2) should answer your question.

OK, thanks. This also means that this tangential snap cannot be used as part of auto snap (it needs additional information). This would be some kind of other snap. Tangential manual if you want. And it would only apply to the moving tool if I understand correctly.

andrew wrote:OK, thanks. This also means that this tangential snap cannot be used as part of auto snap (it needs additional information).

Correct.

andrew wrote:This would be some kind of other snap. Tangential manual if you want. And it would only apply to the moving tool if I understand correctly.

Correct - category like "Middle Manual" ...