Why can I change one dimension, but not the other one?

[stefanome]

In this screencast you can see that I can successfully select one horizontal line and change the vertical dimension, but I can't select one vertical line and change the horizontal dimension.

What am I doing wrong?

[barthbradley]

Label the Dimension and change the Parameter Value.  

[stefanome]

Thanks, I know I can do that, and I have found other workarounds too.

But I would like to understand why this is happening, because I keep getting in this situation and looking for workarounds.

I'm sure there is a better way than keeping doing something, finding out that 50% of the times it doesn't work and looking for a workaround.

[GustavoUbriaco]

there is something blocking those lines 

check these images in this case the dimension is locked, not on your case maybe the EQ is the problem? what happens if you put a label parameter in that dimension?

[stefanome]

Adding a label works fine. I can change the value from the Family Types dialog and it works as expected. As soon as I set the label back to <none> it stops working.

If I get out of the editor I see a 3" dimension instead of the 6" one:

[barthbradley · Accepted solution]

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@stefanome wrote:

Thanks, I know I can do that, and I have found other workarounds too.

But I would like to understand why this is happening, because I keep getting in this situation and looking for workarounds.

I'm sure there is a better way than keeping doing something, finding out that 50% of the times it doesn't work and looking for a workaround.

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"Workaround"? What I told you to do is not a "Workaround".  It's the only way you can do it with that EQ constraint.  If you remove the EQ Constraint, you can change the Dimension.  You can also select the Right or Left Ref Plane (if accessible) and change the Temporary Dimension for the half-width.  

[barthbradley]

FWIW: I would advise against putting control dims in sketch mode.  Instead, align and lock sketch linework to Ref. Planes that are visible outside of sketch mode and then pull labeled dimension between Ref. Planes.  

[GustavoUbriaco]

click and drag the line in my computer happens some similar and now it is working

[barthbradley]

Have you considered Aligning and Locking to Ref. Planes?  It not a "Workaround". Promise.  😉

[stefanome]

"Workaround"? What I told you to do is not a "Workaround".  It's the only way you can do it with that EQ constraint.  If you remove the EQ Constraint, you can change the Dimension. 

That's weird. What is the logic behind it? Is this a documented behavior?

I'm coming from other 3D modeling software similar to Inventor, where duplicating an entity in a sketch is just confusing. If a line in your sketch can be constrained, then you should constrain that without creating any redundant entities.

Sometimes I think that knowing other parametric 3D software is preventing me from thinking the Revit way. Is there any Inventor-to-Revit guide that lists the dos and don'ts?

[lucdoucet_msdl]

@stefanome 

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That's weird. What is the logic behind it? Is this a documented behavior?

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Welcome to the wonderful world of Revit's parametric constraint ecosystem! There is some specific documentation as per this aptly named help ressource:  Constraints

I'm coming from other 3D modeling software similar to Inventor, where duplicating an entity in a sketch is just confusing. If a line in your sketch can be constrained, then you should constrain that without creating any redundant entities.

There is a category in Revit called "implied" constraints that are a result of the way you create the geometry. The simplest example of this is:

1. a line parallel to a reference plane with a dimension string that controls it's distance from the reference plane;
2. mirror that line about the reference plane and this second line will move towards and away from the reference plane as though there exists an "equality" dimension string.

Here is a link to the different types of constraints that Revit presents : Types of Constraints

Sometimes I think that knowing other parametric 3D software is preventing me from thinking the Revit way. 

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Having also used other parametric CAD/CAM software, I agree that you need to avoid analogies as to the way other software work. Analogies may work in a poetic sense but will lead you astray when you try to used them in a logical problem.

In reviewing your screen cast, I would suggest you activate the "Reveal Constraints" mode to troubleshoot.

Then again, I may be that you are constraining something in sketch mode that would rather be constrained outside the sketch environement.

Good luck,

-luc

[stefanome]

Thank you very much!

[GustavoUbriaco]

Exellent information! thank you @lucdoucet_msdl !