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Avoid extruding point at origin of workplane (by DIV)
I have just today started having a go at using SolveSpace.
I am very impressed with the compact size.
After looking at tutorials, I am doing OK so far, but one thing puzzles me.

I create a 2D sketch on the workplane and extrude it, and I end up with not only a 3D object based upon my sketch, but also a line formed by extruding the point located (automatically) at the origin of the workspace.

I don't want the line.
I have tried to delete the line: can't delete it.
I have tried to delete the point: can't delete it.
I have tried to toggle the line/point to 'construction': can't toggle it.

In retrospect I noticed in tutorials the designers will choose one point of their sketch to coincide with the origin point. I can see that by doing that the line formed by extruding the origin point will be 'merged' with an edge/feature of the intended solid object, and thus won't be detectable as a separate artefact.

That strikes me as a 'workaround', rather than an elegant solution.

Question: is there an elegant way to avoid extruding the point at the origin?

Comment: if not, then I suggest that the documentation (reference/tutorials) explicitly mention that placing one of the sketch's points at the origin is not just an optional idiosyncrasy, but rather an important step that should always be followed.
Fri Oct 11 2019, 09:59:39
Symmetry (by DIV)
By the way, a classic example of when this occurs is in creating an annulus (a ring-shaped object).
It seems quite natural to me to place the centre of the two concentric circles at the origin. (It also fits with advice in the reference/tutorial documentation suggesting that symmetry is a desirable feature.)
However, it creates the unwanted line along the centre of the annulus.
Fri Oct 11 2019, 10:04:02
Annulus problem remains (by DIV)
Actually, for an annulus there are two spurious extruded lines that can unintentionally be created from 'reference' points.
As mentioned, one is due to the point automatically located at the origin.
The other is due to the point automatically located at the centre of the circle(s).
Fri Oct 11 2019, 10:21:05
Extrusion of construction lines (by DIV)
I can create a construction line — coloured 'green' by default — in the workplane. The points at either end of the construction line are also green.

I then extrude my sketch (which includes the construction line).

The extended end of the sketch is outlined in white, whereas the extended end of the construction line is green — as it should be. HOWEVER, the perpendicular lines emanating from the base construction line are white! I think they should also be green.
Sat Oct 12 2019, 00:29:26
(no subject) (by Paul)
All points get extruded into lines. The example of an annulus is a good one because there would not be any axial lines if not for this behavior. After you extrude the circles, it's nice to have an axial line which you can select and press D to apply a distance constraint. Without the replication of the center point there would be no way to do that.

Extra lines and points often provide anchors to build more things from, but they can be a bit of clutter at times. You can "uncheck" each group individually in the text window (home) to make these invisible. Or click "hide all" to uncheck everything.

For helical extrusions, a late change was to make sure the point at the center of revolution creates a line like this even if that point was not part of the sketch. This was done for the same reason - to ensure there exists a straight line whose length is equal to the length of the extrusion.
Tue Oct 15 2019, 15:14:38
As 'construction line'? (by DIV)
Hello, Paul.

Thanks for clarifying SolveSpace's design principles.

I definitely agree that having those lines can be useful to 'grab' with the mouse.
They're also useful for specifying constraints (although arguably the points at either end can do almost the same job).

I guess in terms of the clutter I'd be less bothered if they didn't show up as white lines just like all the 'real' bits of the sketch.

Unfortunately it seems currently impossible to define them as construction lines.

To me it seems logical that:

* the points defining the centre of a circle, the origin of a workplane, the end of a construction line, or a control point for a tangent arc should all be 'construction points' (or, at least, toggle-able as such);

* if lines get extruded from points, it should be possible to toggle their construction line status;

* if 3D circles get 'lathed' from points, it should be possible to toggle their construction line status [e.g. currently the control point of a tangent arc creates a white circle when revolved to make a 3D solid].

Alternatively, if you don't want the ability to toggle status in 3D, it would be OK just to base the status of 3D lines on the status of the point in the 2D sketch, provided that it's possible to define points as "construction points".
Tue Oct 15 2019, 20:02:07
I agree (by Ryan)
As a new user this seemed weird to me as well. I spent a bit of time wondering why the lines were floating and did exactly what OP wrote about. Thankfully this post was still here to clear things up. I expected the center lines to be construction lines since they don't exist in physical space. Now that I understand how it works, I don't care too much since it doesn't seem to affect how the STL model are created . Still worth noting because it was a point of friction.
Sat Apr 17 2021, 23:03:23
(no subject) (by Paul)
Another reason to use the origin as a point in your sketch is to fully constrain it and bring the DoF to zero.
Mon Apr 19 2021, 11:51:44
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