How can this line be constrained?

[tbenkerE2YG2]

As poor hobbyist i bought myself a Logitech MX Ergo trackball mouse as a CAD mouse. Today i was practicing with it  by randomly doodling with every geometry and function in the sketch. I draw a house like shape on the right. The sides of the rectangle are equal but not dimensioned. As well as the two lines forming a triangle on top. I applied no dimensions or constraint to them. The centerline between them constrained perpendicular but no dimension as well.

As soon as i dimensioned the distance between the central rectangle and the origin that line became constrained while rest of the shape was still unconstrained. If i double click and select the line, all shape scales up and down when i move the line.

As that line has no defined length or starting point i would expect it to be unconstrained as well i am confused.

I am attaching a screenshot pointing the line I am referring to and the sketch file if anyone would like to check.

[TimelesslyTiredYouth]

I'm guessing Fusion made it constrained automatically somehow?

but I see a midpoint constrain sign ( the upside triangle) forcing to stay in the centre of the line, and it's obviously snapped to the top of the triangle, forcing an automatic coincident constraint I'm guessing.

My guess is that as the line couldn't move anywhere anyway, (as it's already midpoint of line and snapped to a point (the triangle top) it was just made constrained)

Idk how automatic constraining works or even if it exists, but here are a few observations...

*connects both of the shapes in some way, I'm guessing the bottom one is a square, so it connected the square to the triangle (as it hit the traingle top point, causing everyting to scale with it.?

*yeh now after further inspection, I see the two sides of the triangle are the same length and are connected by that point, so if the point goes up the length of the triangle will also increase in poroportion, and as square's automatically have equal constraints, I'm guessing it conneccted the length of the trianglele to the square casuing it to scale upwards, -this is a first for me as I constrain as I go instead of after finishing the sketch, just an guess...

[davebYYPCU]

Don’t forget the endpoints, of any line need constraining too.

That line is only showing as black, as it can’t move sideways.  Both end points are free to change height.

Might help…..

[tbenkerE2YG2]

I am relatively new to Fusion and it sometimes does not react as i would expect. I am still trying to figure out some small things i have not realized/learnt so far. 

As i mentioned, i was just doodling to practice. The initial shape on the left is fully constraint and act as a harbor allowing me to draw some two point , three point tangents etc. After practicing all types of a shape like; all forms of circles, I was deleting all but the initial harbor. The last one I was drawing to practice my clicking precision with the trackball. That's why midpoint and perpendicular were set much before anything.

You are right that the rectangle and triangle is somewhat frozen by the mid point and perpendicular constraints of the line and rectangle sides equal constraints. So it is no surprise that everything scales together. But this is obviously not enough for Fusion (they do not have dimensions) that they are blue. Fusion can not determine where they suppose to be on space. This is exactly the same case for the line as well. That mid point and perpendicular constraints should not be enough to determine where it should be. At least in by brief experience with it, it had never been enough. If this is not a bug but normal behavior based on some principles i had not been discovered yet, this information may help me simplify my design algorithm. 

[etfrench]

The line is constrained, but its endpoints are not.  You can change the size of the rectangle or the triangle and the line will increase or decrease in length, but it will not move horizontally.  Dimensioning one side of the rectangle and one side of the triangle will fully constrain the line.  To fully constrain the sketch, the point above the origin needs constrained on the X axis.  The easiest way is with a horizontal/vertical constraint between it and the origin.

[g-andresen]

Hi,

The important thing is that the point in the square is not aligned with the origin.

günther

[tbenkerE2YG2]

"That line is only showing as black, as it can’t move sideways.  Both end points are free to change height."

That part confuses me. Without the points of the line are fixed to a determined coordinate should not be the whole line blue as well? 

[etfrench]

See post #5😎  The endpoints of the line are not constrained.  The line itself is constrained because it cannot move.  Only its endpoints can move.

[Drewpan]

Hi,

I would strongly recommend that you do the embedded tutorials in the Fusion Documentation and also some of the

Self-Paced Learning to help you to learn fusion faster and better. They can be found here:

It is also much easier for the forum to help you if you attach your file AND a screenshot of what you want to achieve

and what the problem is. You can create a file to export like this:

Time spent on the tutorials and self paced learning will not be wasted. Also check out the three RULES that are pinned to the forum for further guidance.

Cheers

Andrew

[tbenkerE2YG2]

Dear @Drewpan,

I am an enthusiast of 3D printing and 3D design. Self taught as any one I know interested in these and i rely on videos and forums. I indeed did quite amount of self paced learning. The thing " a not completely defined line becoming constrained" was not mentioned in any of them. I was not trying to achieve a certain design goal. I was randomly doodling to practice and get familiar with my new mouse. As soon as i entered a dimension from central point of the rectangle, the line became constrained. Which i believe it should not be. To test my thought process, I draw a 3-tangent circle in the center rectangle. Although it is fixed in the rectangle and scales the whole section when dragged like the line but unlike line  it is still blue. I found this strange and i am trying to understand why fusion regard this line differently. I am not an engineer and my rusted math's from 40 years ago might be failing me to understand.

I am also uploading that version of the sketch now. In fact i had already uploaded a screenshot to show which line i was referring to and the sketch in my very first post.

And about the rules, do you think I broke any rules? If so i am sorry.

@etfrench

I get your point and I agree with that but this means those end points are not regarded as the parts of the line by Fusion. 

[TimelesslyTiredYouth · Accepted solution]

1. About the rules, no-need to worry there, R.U.L.E 1 & 2 as well as 0 are very useful to people new to Fusion or in your case, hobbyists trying to get better and achieve a better workflow in order to avoid issues in the timeline or other problems of sort, and 0 gives more hlepful info.

2.When you add a dimension to a line in Fusion 360, it automatically becomes constrained because the software defines its size and position. A circle with tangents, though, remains blue because it's not fully defined in terms of its size and position. 

3.A point is unconstrained because it can move freely, while a line becomes constrained when you apply a dimension, fixing its position and size relative to other elements. Fusion 360 automatically applies constraints when it detects a defined relationship like a dimension.

in your case this is as the line can move side to side, yes, but the point isn't constrained as it also relates the two lines of the triangle, so multiple lines need to be fully constrained before that point is constrained, unless you used a coincident constrain, as the point controls multiple factors ie,the line and the triangle lines.

so it can't be constrained by only one of the three factors, it's like saying one person is enough to pull 500kg when you actually need 3 people

Tired Regards

Ricky

*With the point needing three factors, that's if the sketch is being constraied after making it, for me I constrain as I go, so The point would be constrained and the triangle lines would just snap to it and I'd continue working, may be a bad workflow, but yeh.

[tbenkerE2YG2]

There is not a defined dimension for the line. I assume Fusion assigns a temporary "derived dimension" for the line as it is somehow fixed to triangle and rectangle and consider it fully defined.

[davebYYPCU]

What do you think they are part of?

A line - consists of the line, 2 endpoints, and a midpoint, that Fusion works with.  
Draw a line from point to point. You get 2 white points, and a blue line.

Gunther showed in the video what an unconstrained end point looks like - white.

For convenience Fusion hides all the points that lay on top of each other - they are still there and to get fully defined, no part movable (constrained).

Articles will be white blue or orange dotted, until you get them constrained, then they are black, if displayed.

Might help….

[g-andresen]

Hi,

1. The circle is already bound to the square by the tangential constraint, but the square is not dimensioned.
2. In addition, the reference point for the distance (444mm) must be bound to the origin via the vertical constraint.

günther

[TimelesslyTiredYouth]

not somehow, there are clear signs, there's a midpoint constraint on the square, and line (the upside down triangle), look at your scrrenshot. And if this is all in the same sketch, the line will have "snapped" to the top of the triangle, as even if there isn't a point displayed there, that is a point, and points snap to eachother, this I'm assuming forced an automatic dimension as you said, between the square and the triangle top, and as the sides of the triangle are equal and square automatically has equal contraints everything scaled up asline increase/decrease in size as there are "automatic"? constraints if you didn't put them, as I've never heard/seen Fusion placing automatic midpoint constraints...

Sleepy Regards

ricky

*A dimension from the line to the top of the triangle making a constraint completely makes sense tho

[tbenkerE2YG2]

@g-andresen, @davebYYPCU,

Thanks for your replies. English is not my native language and the title of the OP might be a bit misleading.  I was not trying to constrain any of shapes on the left.

As @davebYYPCU mentioned, Fusion needs to know the coordinates of the two end points or the dimension of the line, at least coordinate of one endpoints and its angle. For this line, non of these are set. So there is no wonder why the shape is blue and endpoints are not constrained. My question is how come the line itself is black.  My math's says the lines includes their endpoints as well. Thus position of the line in space should be undetermined without knowing the endpoint coordinates. The answer might indeed be; Fusion assigns a temporary "derived dimension" for the line as it is somehow fixed to triangle and rectangle and consider it fully defined.

[etfrench]

The line cannot move!!! Only the endpoints are moving. Try dragging the square or triangle larger or smaller and you will see the line is not moving.

[laughingcreek]

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@tbenkerE2YG2 wrote:...My math's says the lines includes their endpoints as well. ...

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FUSIONS math (and most everybody else's) says a line is infinite in either direction. when you define endpoints on that line, you have a line segment.  we users ( and fusion documentation) are just being lazy when we refer to a line segment as a line.  but the software itself isn't lazy.

[davebYYPCU · Accepted solution]

Thus position of the line in space should be undetermined without knowing the endpoint coordinates.

In your example, not correct.  It is partially determined.
The angle of the line is constrained - vertical

The horizontal position is dimensioned to a fixed position from the Origin.

The vertical positions of the endpoints are not constrained.

When Gunther dimensioned the line, lots of other parts of the sketch also became constrained, turning black.

Fusion uses relationships and existing constraints / dimensions to provide stable behaviour.

Might help…..

[tbenkerE2YG2]

"Fusion uses relationships and existing constraints / dimensions to provide stable behaviour."

thx