Why use "reference planes" in family creation

[sameerkhankhattak]

Greetings everyone,

I am new to Revit Families and would like to ask that "Why do I have to use reference planes in creating any family?". I have seen so many basic revit family tutorials where they just start from reference planes (right,left,top,bottom,front,back) and then define parameters through them. I read somewhere that they give skeleton (i didnt get what that mean) What if I draw/model a geometry and make its dimensions some parameters (say length,width). Would it be good practice or bad and why ? Any other advice would be much appreciated. Have a good day 

[Rab_i]

Let me share my similar quest and see if that helps.

Build a cube that is a solid geometry. Let’s imagine you put a dimension on the top surface of the cube geometry. While continuing adding another geometry, you needed to use some boolean operations. Now all of a sudden, the geometry you were using to drive dimension (the top surface) doesn’t exist anymore. What will happen to the dimension we originally started with. It will be wanting to reference the surface which doesn’t exist anymore.

This is where Reference planes are used. The key is to use Reference planes at only places where we want to make parametric changes. Just for simple dimensions and locking them, you could do with geometry alone. For that reason I personally prefer nesting families. I like building the geometry complexities in its own families. This also means not everything needs to be parametric. 

I hope it helps.

[RDAOU]

@sameerkhankhattak 

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@sameerkhankhattak wrote:

I read somewhere that they give skeleton (i didnt get what that mean) 

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It is more of a concept, but without digging deep into it and the several purposes of reference planes, best would be to focus on the things you did not get...The Skeleton

Its like one saying a body can stand straight mainly thanks to the bones and muscles it has (among other things of course).

• Leaving the bones and taking the muscles out it MIGHT still be able to stand...maybe for a short while if one carefully balances it
• Leaving the muscles in and taking the bones out it MIGHT also still be able to stand but then how long/much can those muscles take to keep it standing

Can you model a family without Reference Planes? yeah!! you sure can...But there are no guarantees how long it would take till they break/fail.

[mhiserZFHXS]

If you want to make a family that is not meant to move at all based on given inputs, then you wouldn't really need reference planes. But the instant you decide you want different things to flex or change, you need to use them. And that decision really needs to be made before you start.

[ToanDN]

A couple benefits of using ref planes and ref lines to plan your family (may have already been said, I did not read every response) :

- you can flex parameters and see if and how they work, in order to proceed/revise without spending too much time modeling

- if for some reason you need to delete the model or linework, you will lose all parameters and constraints assigned directly to those.  using ref planes and ref lines will prevent this to happen.

[RDAOU]

@mhiserZFHXS 

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@mhiserZFHXS wrote:

If you want to make a family that is not meant to move at all based on given inputs, then you wouldn't really need reference planes. But the instant you decide you want different things to flex or change, you need to use them. And that decision really needs to be made before you start.

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Metaphorically speaking: Even if someone is not the thinker type, that someone still needs his brains. It has other viable functions (like keeping that someone breathing). So are the reference planes to a family.

Reference planes are required irrespective if the elements in a family are parametric or not.

[mhiserZFHXS]

I would agree its best practice to just go ahead and use them in all situations, but they're not really needed for something that doesn't "breath".

[s.borello]

So your families can be parametric, and change sizes via parameters.  otherwise you would be creating many families to meet your project needs; I imagine your models would become bloated.