What does constrained on line from point mean?


I get this message sometimes when I am trying to connect two connect two simple lines. I have no Idea what it means for the two end points will not connect when this pops up.


As far as I know this can only be initiated by the user.

Maybe you’re pressing an arrow key as you’re drawing the line? …doing so will get SU to lock the lines travel to a particular axis direction. up arrow = z axis , left arrow = y axis, right arrow = x axis.

The same thing can happen if you hold down on the shift key while drawing the line on an x/y/z axis. [it’s also possible to lock onto other axes]

Either action constrains the line to track on whatever axis you were on. The idea being that SketchUp will lock the lines travel to that axis so that you can drag out the cursor and reference some other point in the model without causing the line to follow along into that other direction of travel.

This is a key aspect to SketchUp’s inferencing system, and it goes a long way towards allowing us to draw without having to get caught up with inputing measurements constantly.


Thanks Jim but actually I am not holding any key down just clicking and dragging. I can’t seem to set up a situation that causes it. It happens in some situations where I am trying to connect the end point of a line to an edge or another endpoint of a line.


It’s an inferencing glitch, I believe it will help if you press twice the down key, or if you zoom closer to connect those two.
I think I get these when I have a line that is closer to one of the axis and the inferencing system tries to keep you on the axis only because the line is too close to easily snap to it.


It’s a combination of inferencing constraints, and it can occur in a number of situations. Basically, though, if you project the location of a point out along an axis (say, by hovering with the Line tool), that’s called From Point inferencing. If you lock that first constraint and then further constrain the projection by stopping it on the intersecting axis, you’ve got the combination of From Point and Constrained on Line. Thus:



The must be a very unique situation for this to occur. I tried to mimic your example but could not get the constrained message. I was able to get the from point message.

I guess the question is how do you get around it when it happens? ely862me has some suggestions that I will try next time.


simple answer: wiggle the mouse a bit and/or zoom in.

These tool-tips pop up all the time to let you know what the current inference is and let you know that the program has recognised you are over a line/point/face/…

The term “Constrained” means that when you move the mouse, it will keep the cursor/insertion point on the vector that your mouse has been travelling along - it’s part of the inference system that helps you place points in relation to what you have already drawn.
The “Constrained” text will (only?) show up when you use one of the arrow keys (up=blue, right=red, left=green, down=pink)

the “on line” bit means that the original vector that you have started to move the mouse along is based on an existing line

the “from point” bit means that your current cursor position is pointing to an end point (rather than a face or another line or mid-point or component or…)

Generally this is a good thing and it means that you are snapping to a point and your resulting geometry will all match up and form faces/shapes without gaps or extended bits of line. Most tidying and errors in creating models arise from ignoring these tool-tips and thinking that where they have clicked is an end point when it’s not. I have seen (and created) waaaaaay too many models that don’t pay attention to this.


The idea is not to get around it but to use it when you need to. It’s not a “glitch”; it’s part of the 3D drawing control system, inferencing. That you have not yet mastered the technique is simply evidence that you have a ways to go up the learning curve. Don’t expect it to all come immediately. Keep practicing.

You need to lock the first inference with the Shift key before you can get the second inference from a second point or edge.



Here you can exactly see why I said it is a glitch.
And you don’t need to lock the inference with the Shift key, it just stick trying to follow the axis inference.
In this case only zooming closer will help connect the two endpoints.


Nonetheless, that tool tip is an accurate description of the constraints acting upon your line drawing operation and is the same message you would get anytime you extended an edge along an axis and stopped it at the projection of a point. Obviously, your intended target is within the gravity range of the axis, so the mouse pointer stays snapped to the axis even without the Shift-lock until you zoom in enough to show some daylight between the points. That’s all normal behavior: it’s not a glitch because everything is acting as intended (as the program developers intended) and in a predictable manner.

That conflicting inferences can result in the wrong pick unless you zoom in to get the right one is a general condition that pertains throughout SU in a range of situations. It is not peculiar to that one tooltip or that one form of conbstraint. In general, if you get the wrong tooltip, indicating the wrong inference, and you still go ahead and click the mouse, whose fault is that?



The main problem I had when starting* was not waiting for a tool-tip and clicking, expecting it to snap to the correct point… only to find that it was ever so slightly out when I had then done another 500 operations and something didn’t quote match up… :sigh:

{* and I never do it now. Nope, never, ever, ever.}


Yeah, there is sometimes a lag while the inference engine figures things out. If you get going too fast it is easy to get ahead and then you get imprecise points. (Nah, would never happen to me…)


Huh? Never, ever?
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