Sketch should show "Constrained".

[huguesacker]

Hi,

I have an issue on several times on a sketch which is (supposed to be) constrained, and yet, does NOT indicate fully constrained and also indicating some lines are not constrained (meaning blue color, instead of black).

When I try to move sketch components it is impossible, and also, if I try to add other measures, like angles, it says that it is over-constrained: meaning that it is indeed, constrained. This is surprising; do I have something wrong ?

Please see the picture below !

Thanks.

Hugo

[whittakerdw]

The sketches can be constrained by adding dimensions and constraints. Not only dimensioning the lines themselves, but dimensioning them around a center point such as (0,0) on the grid. dimensioning the x and y dimensions to a point of each line will constrain those lines.

[whittakerdw]

I drew a random sketch similar to what you had and all I had dimensioned were the x and y. I didn't add any angles. After dimensioning the x and y for all the lines, the lines were black.

[HughesTooling]

@huguesacker be a good idae to export the model as a f3d and attach so we can see exactly what you have.

Mark

[carl.j.barker]

Hmm This is odd.  While I agree with Fusion that those lines should be blue, they are not constrained and can easily exist else where at those lengths and with tangent ends. It is odd that it seems no additional dims can be added to constrain them. Indeed you should be able to drag them about. This is interesting since I'm a sheet metal type person and 2D geometry (or other peoples idea of 2D geometry) is my bread and butter or more usually the bane of my existence and while a drawing dimensioned like your sketch should/would/maybe never happen it still shows something broken in fusion. Or I have had too many Friday night beers and am missing something.

[huguesacker]

Thank for all. I made a new project in the attachment of this post. It appears, that this behavior is intermittent: in certain rare cases, one of the lines is black, but most of the time, they are blue...

I had already seen that before. It should be constrained.

Hugo

[huguesacker]

Impossible for me to turn the 2 lines black. Did a couple of times new designs, and still same pb. The sketch is constrained but does not show it for me... Impossible to move sketch components, and any other dimension is over-constrained...

[TheCADWhisperer]

I was easily able reproduce the unexpected behavior in Fusion.

I  then did the sketch in Autodesk Inventor Professional and the sketch was fully constrained as expected.

Interesting case because although there are 4 possible solutions - it is not possible to get from one possible solution to the other possible solution without violating the given constraints. (dragging endpoints)

[chrisplyler]

@TheCADWhisperer  is correct, except that I believe this behavior is exactly what should be expected.

Those four straight lines are NOT fully constrained in the picture.

Sure, you can't drag them. But there are four possible solutions to the sketch in the picture. Either of the two joint intersection points could be flipped downwards such that the connecting arm would be in a "mirrored" position. The reason that you can't drag them is because none of the infinite possible points they could be at BETWEEN the acceptable solutions...is acceptable.

To fully constrain that sketch you need add a construction line coincident to the origin or the center point of one of those circles, constrain that line horizontal/vertical, and give an angle dimension from it to at least two of those four lines.

[chrisplyler]

@huguesacker  Might be educational....

@jeff.strater  Please watch from the 7 minute mark. TWO bugs?

[carl.j.barker]

Adding construction circles fully defines.

Of course adding construction circles after the lines is a bit backwards.

[chrisplyler]

It's not evident to me WHY the construction line circles make the connecting arm any more defined than it was before. In fact, the construction line circles make the alternate acceptable points obvious, and don't really do anything else.

[melvinbrian3d]

---

@carl.j.barker wrote:

Adding construction circles fully defines.

Of course adding construction circles after the lines is a bit backwards.

---

it work, But honestly i don't get it O.o

[huguesacker]

@melvinbrian3d@chrisplyler@carl.j.barker@TheCADWhisperer@HughesTooling

Thanks to all. For me, there is something broken in the sketch engine. Of course it is not important but. If we really look for something wrong, it is really easy to find. Look at these 2 pictures: why a not-fully-constrained line turns black ?

and why fully constrained arcs turn blue, since they were fully constrained before ? That's weird...

[HughesTooling]

Be a good idea to upload the file again. Are the arcs part of a circular pattern?

I've brought up several times that 2 colours are not enough to show degrees of freedom left.

Here's an example. A vertical or horizontal line drawn from the origin show constrained if though it's length is not fixed if you add a dimension the line looks exactly the some, the end point doesn't change colour. If the is another line drawn from it with it's length defined it will not show as constrained because the horizontal line has no length dimension. 

Mark

[HughesTooling]

Similar to my example the line endpoint and direction are fixed by the tangent and to the end of the arc only its length is free but the constraint colouring status will show it as constrained. I've used another program the used 3 colours for DOF and it made adding constraints\dimension a lot easier.

[huguesacker]

@HughesTooling

Here is the project file attached.

The arcs are not a pattern, they are just drawn, one by one, like we do with a classic compass on paper. I agree with your remark. Some time, colour do not reflect reality of constrains; this is a proof. Also, the state some time depends of if we have the state after drawing, or if we obtain the state after undo's or redo's: at a moment we have a certain colour, and for example erase something, the colour changes, and undo, and the colour is not reset like previous.

[melvinbrian3d]

[HughesTooling]

I found something odd at the end of this screencast. At the start I try adding tangent lines from the end of the arc in your sketch, these should be white because only their length is undefined. Next I reconstruct your sketch and create a new sketch in another design and get similar results but changing the diameter to 6cm or 60mm gives the correct colour status! So definitely something a bit bugged. @jeff_strater what do you think. Sorry the screencast's a bit long but it didn't go quite how I thought it would, I tested before with a 60mm circle and all worked OK just in the screencast I tried a 40mm circle and got different results.

Mark

[huguesacker]

@melvinbrian3d I did not put the dimension at the intersect to illustrate and show the fact that one of the lines is black even if it should be blue; the point was: certain times, objects are black when they should be blue, but also the opposite (blue instead of black). Also, some of the arcs turn blue, even if they were black and fully constrained before too. It looks like certain actions corrupt what is known to be ok: here deletion of a dimension turns arcs into blue.