what does the little lock icon do when I draw something to the reference plane?

[yimingZHW6B]

It looks like my lines and other geometries snap to the reference plane just fine as long as the reference plane is highlighted when drafting. Without locking, the lines still moves with the reference plane. Then why do I still see a lot of people lock everything to the reference plane? Any insight is appreciated!

[RDAOU · Accepted solution]

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@yimingZHW6B wrote:

...Without locking, the lines still moves with the reference plane. Then why do I still see a lot of people lock everything to the reference plane? Any insight is appreciated!

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@yimingZHW6B 

That is not true. Elements do not get locked to reference planes intuitively and without the user explicitly locking them (see below GIF, regardless if it is a System family, a line, an inplace component...etc, none locks by default to the plane and none moves with it.

What you might have missed out on or got confused with are automatic constraints and/or the auto join property of lines (detail lines, symbolic) where any newly added lines which are connected and coolinear with A line which was previously locked to a plane will be LOCKED to that line and not to the plane. However, this does not apply to geometries. 

Locking to the reference plane, when it doesn't over constrain the elements,  is always the recommended approach

[blank...]

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@RDAOU wrote:
That is not true. Elements do not get locked to reference planes intuitively and without the user explicitly locking them

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But, sometimes they do.

I had a door family with geometry moving in it, a sweep, and for the life of me I couldn't figure out what makes it move because no element of it, or its sketch, was locked to absolutely anything.

Uploaded the family here and the consensus was that sometimes Revit thinks it's smart and sometimes when you place something near enough to a reference plane it will move with it even though you didn't lock it.

[RDAOU]

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@blank... wrote: 

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But, sometimes they do.

I had a door family with geometry moving in it, a sweep, and for the life of me I couldn't figure out what makes it move because no element of it, or its sketch, was locked to absolutely anything.

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@blank... 

No, they don’t… not on their own. Not being able to figure out how a sweep got locked does not mean that geometries have an innate auto-lock property.

That does not happen randomly or automatically—it is triggered by user actions. For instance: Deleting the host makes the sweep unassociated. Realigning it to a reference plane without locking it to the plane, or rehosting the sketched path on that plane, will not cause the sweep to move along with the plane.

If it had an innate locking mechanisim as the OP suggested, shouldn't it simply relocks itself to another refernce plane without using the lock tool/option? 

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@RDAOU wrote:

@blank... 

No, they don’t… not on their own. Not being able to figure out howyour sweep got locked does not mean that geometries have an innate auto-lock property.

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Would you mind taking a look at this family, it works fine for me in this case so I just accepted that it works because Revit locked it without locking it, but would love to know what is actually going on if that's not the case.

Change the height parameter, an the sweep goes along with it. Sweep path isn't created by picking 3D edges, and it's not locked to ref plane.

[RDAOU]

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@blank... wrote:

Would you mind taking a look at this family, it works fine for me in this case so I just accepted that it works because Revit locked it without locking it, but would love to know what is actually going on if that's not the case.

Change the height parameter, an the sweep goes along with it. Sweep path isn't created by picking 3D edges, and it's not locked to ref plane.

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@blank... 

That is not related to the original topic of this discussion (the purpose of the lock icon and geometries auto-locking to planes). In your case, this is Revit preserving the logical constraint, based on its internal dimensions and not a locking mechanics due to proximity to a reference plane. And yes, this is a smart behavior that can save the user a lot of trouble.

Normally, when in a view there is no associated work plane to host the path, Revit would ask you to pick one else you cannot place the Sketch Line.. This sweep was originally locked/hosted to either a reference plane, a 3D face, or the edge of a geometry, which was later deleted by someone, causing it to become <not associated>. While its original constraints are lost, Revit is simply preserving the logical constraints with respect to the height parameter similar to how it would when a user deletes an EQ dimension string while maintaining the equality constraint.

Note: this has nothing to do with how close the sketch line is to the reference plane either. Edit the sweep and pull that path 1m away from the plane; it would still adjust/move with Height parameter regardless of how far or close it is to the ref plane. (See GIF Below)

What could happen:

• This sweep will function until it eventually breaks (unpredictably).
• What it has constrained itself to might or might not be convinient for the user or the way the family function (in your case the height seems convinient)
• It will not be a fail-safe family until you reassociate the path with a host. (On its own, it will not lock or host itself to anything.)

Edit: @blank... See below...Recreating the behavior of the family you posted (reference plane is irrelevant as you can see)

[blank...]

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@RDAOU wrote:

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I see, thanks for explaining it!

[RDAOU]

@blank... 

You are more than welcome

[yimingZHW6B]

Hi @RDAOU , thank you for this! Yesterday, I was working on my home machine, and I was creating a simple detail item, i didn't lock any lines to RPs but the line still moves with the RP. Today I worked on another machine and you are right - I do need to lock lines to RPs. I'll look closer at the settings on my home machine, wondering if there is any system configuration causing this.

[RSomppi]

In the family editor I've seen this auto locking behavior. Revit will automatically add "inferred constraints" (may not be correct terminology) and lock elements to reference planes. I've seen elements get locked to a plane as I'm moving the reference plane by it as in they were not constrained before and became constrained as I moved the plane by them. If you draw items aligned to reference planes as you draw them, they will be constrained to the planes. 

[SteveKStafford]

Many replies, I'll add this. Automatic Sketch Dimensions (ASD) start to appear in a family as soon as a parameter is invoked to control something. Each view can display them, Annotation Categories in Visibility/Graphics. Revit adds them "internally" to constrain elements that we don't constrain explicitly with align/lock for example. If you have constrained everything well you'll find few if any ASD's.

[RDAOU]

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@yimingZHW6B wrote:

..... I'll look closer at the settings on my home machine, wondering if there is any system configuration causing this.

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I do not believe this is a setting you can disable. The only way around it is to lock elements to reference planes for them to function as intended—or at least as you wish or expect them to. This leads back to your original question: "Why do I still see a lot of people locking everything to the reference plane?" The reason is that it is the recommended approach for parametric modeling (at least in Revit).

Leaving it up to Revit’s intelligence is like counting on fate. It might constrain an element to a dimension or parameter that it considers logical, but that doesn’t mean it will always be the most convenient constraint for you. In @Blank...’s family, maybe the height or rough height was convenient, but this is/will not always the case in all families.