Help with formula..

[Secttor]

Hy . I really need a formula for this situation and also hope it's possible :).

- so.. I need B (200) to grow until it reaches the 45 length extrusion and after that grow in the opposite direction by growing A(360) too. By growing A the portion between B and 45 should modify.

- the problem is related with A which is an instance parameter same as B.. so the user can change it independently. Hope..won't reach an overconstraint situation.

* If any of above isn't possible..maybe a condition for B to grow not more than A - 45? (but also remain instance).

Any suggestion is welcome!

[CoreyDaun]

This may be possible, but a little more information is needed:

- What determines the initial value of "A"? Is this a user-inputted value?

- Is the user expected to control this Family by inputting a value for "B"?
- When "B" reaches its 'max length',does it continue to increase, essentially 'pushing' "A" along with it?

[Secttor]

- Yes.
- Yes.
- and Yes.

" I need B (200) to grow until it reaches the 45 length extrusion and after that grow in the opposite direction by growing A(360) too. By growing A the portion between B and 45 should modify."

hope will not overconstrain 😄

[CoreyDaun]

If the user is supposed to be able input values for both "A" and "B", then these Parameters cannot also be controlled by formulas. What I will suggest, in this case, would be to create separate Parameters for 'User Input' and then use those values to drive the formulas within the Family. See the attached example Family (Revit 2013), which is a very crude mock-up of the situation as I understand it. All Parameters are Instance Parameters and "A" and "B" are Reporting Parameters. Play around with this file and see if it works anything like what you have envisioned.

[Secttor]

Yes.. something simmilar..but with the addition for B1.. to grow in the opposite direction when it reaches..355 (which is the limit for growing in this direction.."touches 45").. but yes.. this is nice too 🙂

1. Also..which version of Revit MEP do you recommend..in terms of stability and .. logical behavior 🙂 ? 2012 > 2015?

[CoreyDaun]

"B1" and "B2" combined make up the dimension "B". "B1" begins to stretch the Extrusion once "B2" hits its limit, which is "A" minus 45. The reporting Parameter "B" will display the appropriate length.

Now that we're getting into the details here, is that 45 width extrusion supposed to remain in place, unmoving? What is the intended origin point of this Family?

[Secttor]

is that 45 width extrusion supposed to remain in place, unmoving?

Yes..

What is the intended origin point of this Family?

Here

[CoreyDaun]

OK, my crude example Family is designed with the origin towards the bottom. See the attached revised, simplified Family. "B" is directly controlled by the user whereas the desired value for "A" is inputted by the user, but then the formulas calculate what "True A" should be, using the formula:

= if(B > A - 45 cm, B + 45 cm, A)

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Secttor wrote:

"1. Also..which version of Revit MEP do you recommend..in terms of stability and .. logical behavior 🙂 ? 2012 > 2015?"

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Sorry, I didn't mean to ignore your previous question. I would say use the latest version you can, keeping in mind that Revit Projects and Families cannot be saved to a previous version. There are many improvements and changes bewteen releases, and modeling your Families is an ancient version limits what new features you can take advantage of, but on the other hand, it would allow you to use the Family in any version of Revit.

I will share this; I created many, many lighting fixture Families back in Revit MEP 2012. Now, every time I load one of these Families into Revit 2013 or 2014, something has always gone wrong, and I have to dissect the Family to find the cause. Sometimes the solution is as easy as opening the Family in 2014, opening the nested components, simply load them back into the host Family, and re-save the Family. It has been quite a pain, though that may be in part due to the elevated complexity of the Families.