IV11 SP2 - Silly midpoint sketch constraint issue!

[RobSinglehurst]

I drew an arc on a line that already had a midpoint constraint. I then tried to use the coincident constraint to fix the arc centre to the midpoint of the line and got the following error (see attached)
Easy enough to work around but why should this happen?

Cheers,

--Rob Singlehurst

[Anonymous]

Rob,

On recreating the same situation here I see that the two points have coincident constraints on the line. Probably the arc center inferred it and you probably put the Midpoint constraint on the line. This tells us to fix those points on the line. Now with applying the coincident constraint of one point to another, we get into a overconstrained situation. We got to break something. So we warn the user to either remove the coincident constraint at the arc center or at the midpoint which lets you do what you want.

I have seen this many times in other sketch situations too. One possibility is we could let users override the existing constraints. i.e. in this case break an existing relationship to satisfy a new one.

Thanks
shekar

[RobSinglehurst]

Thanks for your qucik response Skekar,

I see what you're saying but I think that the behaviour is still wrong. The end of the line is constrained to the vertical line but free to move up and down it. So why can't it move down to satisfy the already existing midpoint constraint?
I placed a point on the vertical line and dimensioned it from the top and the coincident constraint works ok then.
And also the end of the line can be constrained to the top or bottom of the vertical line without any problems.
There must be something "odd" in the way that the midpoint constraint works.


Cheers,

--Rob Singlehurst

[Anonymous]

>The end of the line is constrained to the vertical line
I see a single vertical line (1 end out of the 4 lines that make the rectangle) and two points on it. One point is the center of the arc. The other is a midpoint. Is there another shorter vertical line there? i.e. in addition to the right vertical line of the rectangle between the two points? Thanks.

shekar

[RobSinglehurst]

Sorry, I should have said that I tried that after your post. You are correct in that in the original screen shot there is just the midpoint and arc centre.

Cheers,

--Rob Singlehurst

[Anonymous]

In the sketch if you do F8 you can see all the constraints. Without examining that I can't tell for sure whether its an issue in the software or its really a overconstrained situation. From your explanation about the line it dosen't appear like but one need to look at all the constraints thats being there. Sounds like a simple file so could you please attach it so that I could see if this warning is valid or not. Thanks.

shekar

[RobSinglehurst]

Shekar,
I've attached a zip file with the original arc issue and I've also created one with the line issue. Please let me know what the outcome is.

Cheers,

--Rob Singlehurst

[Anonymous]

Rob,

I see coincident constraints at both points in both files. For the file MidPointConstraintArc.ipt please see line arccoincident1,2.png.
For the file MidPointConstraintLine.ipt please see the other three images. I have highlighted the coincident constraints.
When I apply a coinicident constraint from the arc center to the vertical line midpoint (or Line end to the vertical line midpoint) for some reason it is thinking it has to move the midpoint to the center of the arc instead of vice-versa.

This needs more investigation. I logged 907654.

Thanks.
shekar Message was edited by: shekarsub[Autodesk]

[RobSinglehurst]

Thanks Shekar,
I thought that this behaviour wasn't quite "as designed"!

Cheers,

--Rob Singlehurst