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Constrain two points relative positions on a plane (by Ken Kolbly)
I have been a modest user of AutoCAD in 2D for a *ahem* VERY long time!

For a new project I want to use SolveSpace to build a 3D model based on my AudoCAD drawings.

So far what I have done is imported my DXF's, created some arbitrary reference lines and then added constraints until my drawing was stable. It is tricky adding the right constraints to both be stable and not be over-constrained.

For example, sometimes the imported line segments will already have point-coincident constraints on the endpoints and sometimes not. I struggle with adding a constraint to two points that are on top of each other. It's usually a multi-step process to do so. The picture shows what I have accomplished so far with three separate DXF files. Each DXF was imported into several workplanes to get the different extrusion depths. Then I "assembled" the objects. This all took a lot of hours, of which at least half was learning what worked and what didn't. Multiple start-overs! I'm very happy with how it's coming together. But I have at least another 20 or 30 drawings I need to bring in to build the full product.

I've done a lot of research but I must not be asking the question the right way.

My question is...is there some simple or direct way to constrain the relative position of two points on a plane? The ability to do so would greatly simplify the importing of the DXF files.
Mon Jan 25 2021, 14:25:28, download attachment RA_Assembly.png
(no subject) (by Tom)
The only way I know to constrain two points coincident is to select each one and then constrain. If they're very close, then that means you have to drag them far enough apart to individually select first.

But do you actually have to add constraints? Obviously it's better to have constraints, but you should still be able to extrude the section without that. If you can't, then maybe there's actually a small gap, and you can see it if you zoom way in?
Mon Jan 25 2021, 15:23:30
(no subject) (by Ken Kolbly)
The problem isn't constraining the points coincident, the problem is constraining them NON-coincident!

Envision a 2D outline created from a series of line and arcs. If all the end points of the lines and arcs are constrained coincident, closing the structure, the shape of the structure is still **very** malleable. Attempting to move the structure can completely distort the shape.

Continue to add additional constraints to the lines and points, such as Horizontal, Vertical, length, diameter and so forth and the shape is less likely to change when you move it.

The only technique I found that works consistently was to add a construction line and then add distance constraints from each end of the line to the points that needed to be locked. Forming a series of triangles. (See picture for a simple example)

Reading through the bug/feature requests I just discovered "Lock Point Where Dragged". I've experimented with it a little and it's not exactly what I want but it may be useful in reducing the sheer volume of constraints I have to add.

Consider two points that are already constrained to a plane. If I could readily simultaneously constrain the Delta-X and Delta-Y between the two points then I could lock the shape of my object so that it would not change when moved.
Mon Jan 25 2021, 16:26:54, download attachment NorthBearingPlate02.png
(no subject) (by Andrew)
Constraints can take a bit of thinking about to successfully constrain a drawing. They do become easier with practice. While not your dimensions, the attached drawing shows a way of constraining your example. An alternative would be to give the radius of the arch, rather than the dimension of overhangs, and it depends on what is specified.

If you need to position on the plane, or in 3d space, you can set the distances of a point from the axes.
Mon Jan 25 2021, 17:25:53, download attachment constraints_example.slvs
(no subject) (by Ken Kolbly)
Definitely a lot of thinking!!

Your example was pretty good. I like the use of "equal length" constraints.

I ended up adding a "Horizontal" constraint to the bottom line to prevent dragging it's end points around and thus changing the angle of the arc.

However, I cannot seem to prevent the distortion shown in this example. I tried to constrain the radius of the arc, the symmetry of the bottom line, the distance between the bottom corners and the arc ends and even tried "Lock where dragged" a few places. All fail as "over constrained" but yet there is a second solution that works!

Do you have any suggestions as to how to lock this down a little harder?
Mon Jan 25 2021, 19:02:23, download attachment constraints_example_distorted.slvs
(no subject) (by Andrew)
Where if you drag a point with a quick flick the constraint gets reversed. A quick flick the other way will reverse it.Note a slow drag will not cause this to happen. If you check the properties for the sketch you will see there are no degrees of freedom left.

I can't decide whether this is a bug, or a useful feature for correcting problems when a resize causes similar changes.
Mon Jan 25 2021, 19:35:32
(no subject) (by Tom)
You can constrain delta-x and delta-y between two points using two projected distance constraints--select the two points plus the x or y axis (from the red-green-blue axes at the origin) and constrain distance.
Mon Jan 25 2021, 20:46:24
(no subject) (by Ken Kolbly)
Thank you Tom!

That does exactly what I was looking for! I did have to separately constrain the Delta-X and the Delta-Y but that was a lot simpler then what I was doing before.
Wed Jan 27 2021, 19:08:06
(no subject) (by ruevs)
https://solvespace.com/2d.pl
https://solvespace.com/constraints.pl
Constraints section here:
https://solvespace.com/constraints.pl
An example of a rather complicated fully constrained sketch:
https://github.com/solvespace/...ues/841#issuecomment-742153838 (see previous posts too)
Mon Feb 1 2021, 13:26:37
(no subject) (by ruevs)
Constraints section here: https://solvespace.com/ref.pl
Tue Feb 2 2021, 01:28:46
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