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Category: Tutorials

  • Revit Families 102 – Revit Experts don’t Use Locks

    In May I published my picks for Best Revit Blogs on the Web.  Coming in at number 2 was The Revit Kid and Jeff’s Lock Noob Classic Thong.  I still try to read everything Jeff writes but I thought I might stir up a little controversy and make the argument that, contrary to what the thong says, a Revit expert is one who doesn’t use locks.

    I think that Jeff has it backwards.  In my experience the newcomer to Revit wants to lock everything.  I think the initial instinct is to not trust Revit and just lock things down.  Later when this user tries to change something they get a string of messages telling them constraints aren’t met and they end up getting frustrated and removing all the locks anyway.

    therevitkid-locknoobthong

    I’m sure Jeff would argue that the Revit Expert knows how to use locks properly.  I would agree that as you experiment with Revit you learn when to lock and when not to lock.  With Revit family creation that time is only as a last resort.

    So what to do instead of locking?

    1. Reference lines and planes:  Hosting and aligning geometry to reference lines and planes automatically creates a strong connection between them.  The link isn’t quite as strong as a lock, under some conditions it will detach.  But for most purposes it works just fine.  Align geometry to a reference plane and flex your model.  You’ll be surprised how often this works.  Carl Gibson has a great overview of the types of Reference lines.
    2. Parameters:  Instead of locking a dimension to a fixed dimension assign a parameter to it.  Using parameters gives you flexibility to easily change things later, and more importantly it lets the user of the family know what’s going on inside it without having to edit the family.  For example, create a a parameter called Table Thickness and give it the formula 0′ 2″.  This tells the user that the Table is 2″ thick and locks it from changing.  Note that locking a parameter with a formula locks it across all types in the family.

    Locking does have it’s place, but I always try to make a family work without locks first.

  • Revit Families 401 – Data Validation

    As I mentioned in a follow up comment to Revit Families 103 – Formula Basics, Revit still doesn’t allow you to do data validation on values or formulas in families or on table data.

    Still, you can build some functionality into your families to ensure that a value never exceeds a specified range or create warnings for the user of your family.

    Lets start with a simple example.  In the plan view below I am showing a basic table.

    Screen1

    Lets say in this example that we never want the table’s width to be greater than 1/2 the depth.  We have a few choices.

    1. Don’t do anything
    2. Display an error message for the user
    3. Default to another value

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  • Revit Families 103 – Formula Basics

     

    Update: 4/12/11 for Revit 2012 and added more examples.

    I love formulas, they let you do some really fun things.  The formula I mentioned in my last post calculates the overall width of a family taking into account if the family has one or two loops toggled to be visible.  Formulas let you create a family that is truly flexible and has a lot of built in intelligence and a few safeguards.  They can also make using the family a lot easier to use by maintaining relationships between elements or calculating details about the family like area, volume, etc.

    I do some pretty advanced stuff with formulas, but we need to get the basics under our belt first.  Most of this post is from the Revit Help files.  To save you the trouble of looking it up, I’m putting it here.

    Keep in mind that Revit is aware of units.  So to avoid getting an inconsistent units error remember to divide and multiply when appropriate.
    For example, these are correct formula:

    (Length_A * Length_B) = Area_C
    (Length_A * Length_B)/1 = Length_C

    Basic opperators:

    + Add: 15′ + 0′  6″ + Length sin Sine: sin(75)
    – Subtract: 1′ 2″ – Width cos Cosine: cos(75)
    * Multiply: Length * Width tan Tangent: tan(75)
    / Divide: Length / 8 asin Arcsine: asin(75)
    ^ Exponent: x^y, x raised to the y power acos Arccosine: acos(75)
    log Logarithm: log (100) atan Arctangent: atan(75)
    sqrt Square root: sqrt(64), square root of 64 = 8
    exp E raised to an x power: exp(2)
    abs Absolute Value: abs(-2), will return 2
    pi pi: pi() * (Radius ^ 2), the formula for Circumference

    Conditional Statements

    A conditional statement uses this structure:

    IF (<condition>, <result-if-true>, <result-if-false>)

    This means that the values entered for the parameter depend on whether the condition is satisfied (true) or not satisfied (false). If the condition is true, the software returns the true value. If the condition is false, it returns the false value.

    Supported Conditional Operators

    < Less Than
    > Greater Than
    = Equal to
    / Divide: Length / 8
    AND Both statements are true
    OR One of the statements is true
    NOT Statement is false

    Conditional statements can contain numeric values, numeric parameter names, and Yes/No parameters.

    Currently, <= and >= are not implemented. To express such a comparison, you can use a logical NOT. For example, a<=b can be entered as NOT(a>b).  For more information see “Revit Families 402 – Greater Than or Equal To”

    Sample Conditional Statements

    Simple IF Statement
    IF (Length < 30′, 2′ 6″, 4′)

    Formula That Returns Strings
    IF (Length > 30′, “This thing is tall”, “This thing is short”)

    Using logical AND
    IF ( AND (x = 1 , y = 2), 8 , 3 )

    This will return <true> if both x=1 and y=2, else <false>

    Using logical OR
    IF ( OR ( A = 1 , B = 3 ) , 8 , 3 )

    This will return <true> if either A=1 or B=3, else <false>

    Nested IF statements
    IF ( Length < 10′ , 1′ , IF ( Length < 20′ , 2′ , IF ( Length < 30′ , 3′ , 4′ ) ) )

    Returns 1′-0″ if Length<10′-0″, 2′-0″ if Length<20′-0″, 3′-0″ if Length<30′-0″ and 4′-0″ if Length>30′-0″

    IF with Yes/No condition
    Length > 10
    (Note that both the condition and the results are implied.)

    Returns checked box <true> if Length > 10

    NOT with Yes/No condition
    not(myCheckbox)

    Returns checked box (<true>) of Yes/No parameter “myCheckbox” is unchecked, and it returns <false> if “myCheckbox” is checked.

    Rounding

    Prior to Revit 2012 the only way to round numbers was to pass a number through an integer parameter.  The integer parameter always rounds to the nearest whole number with the standard mathematical rounding rules of:

    Down -> for fractions of 0.0 to 0.49 and -0.5 to -0.99
    Up -> for fractions of 0.05 to 0.99 and -0.49 to 0.0

    As of Revit 2012 we now have three additional functions to use!!

    Note that “x” is unit-less

    Round(x)
    Rounds to the nearest whole number per the standard rules mentioned above.

    round (1.1) = 1
    round (1.5) = 2
    round (1.7) = 2

    round (-1.1) = 1
    round (-1.5) = 1
    round (-1.7) = 2

    Roundup(x)
    Rounds to the largest whole number greater than or equal to “x”.

    round (1.0) = 1
    round (1.5) = 2
    round (1.6) = 2

    round (-1.0) = 1
    round (-1.5) = 1
    round (-1.6) = 1

    Rounddown(x)
    Rounds to the smallest whole number less than or equal to “x”.

    round (1.0) = 1
    round (1.5) = 1
    round (1.6) = 1

    round (-1.0) = 1
    round (-1.5) = 2
    round (-1.6) = 2

    Some Extra Stuff

    • Revit allows you to use integers, decimals, fractional values, and parameter names in formulas.  You can enter dimensions in feet and inches just like you do in dimension strings.  Remember that parameter names are case sensitive.
    • You can enter a value in a formula essentially locking it across all types.  This is an alternative to locking the dimension in the model.
    • Instance and Type parameters can not be used in the same formula.
    • It’s a good idea to not name your parameters with any of the mathematical operators in this list.

  • Revit Families 302 – Naming and Grouping Parameters

    I started a post a couple weeks ago on tips for creating families in Revit but I didn’t get very far.   Our friends over at Inside the Factory are more disciplined bloggers than I and beat me to it. Erik Egbertson put together a great post of Family Editor Tips.  He talks about flexing a family, placing Constraints Consistently, not over constraining, avoiding chaining references, shortcuts to duplicating elements, shortcuts to creating dimensions, labeling shortcuts, and a couple other tips.

    Initial Setup and Naming of Family Parameters

    One thing that Eric didn’t cover in too much depth was naming and grouping of parameters.  I also use Eric’s programming syntax method for naming parameters except I usually capitalize the first letter.  It doesn’t make much difference really, I just like the look of it in my parameter list.  For example, “WindowTrimWidth” instead of “windowTrimWidth”.  Although Revit supports parameter names with spaces, I think having your parameters as one “word” makes writing formulas easier.

    The first thing I do when setting up a new family is place all of my reference planes, dimensions and parameters.  I flex the model with the reference planes and make sure it works.  If it does then I’ll start modeling the geometry.

    When I first add parameters I don’t write out the whole name for parameters that I know will involve some calculations.   Sometimes formulas can become quite complex:

    if(and(LoopOne, LoopTwo), DepthDefault, if(or(LoopOne, LoopTwo),DepthDefault- DepthBikeLoop, Diameter))

    Make one error in typing this out and you have a hard time debugging it.  I start with naming my parameters with shortened names like LO, LT, DD, etc.  This makes the structure easier to see.

    if(and(LO, LT), DD, if(or(LO, LT), DD – DBL, D))

    Once I know everything is working I rename the parameters and they are automatically updated in my formulas.

    Grouping of Family Parameters

    Currently Revit only allows us to categorize parameters in a set list.

    • Analysis Results
    • Analytical Model
    • Constraints
    • Construction
    • Dimensions
    • Electrical
    • Electrical – Lighting
    • Electrical – Loads
    • Electrical Engineering
    • Energy Analysis
    • Fire Protection
    • Graphics
    • Green Building Properties
    • Identiy Data
    • IFC Parameters
    • Layers
    • Materials and Finishes
    • Mechanical
    • Mechanical – Airflow
    • Mechanical – Loads
    • Model Properties
    • Other
    • Phasing
    • Photometrics
    • Plumbing
    • Rebar Set
    • Slab Shape Edit
    • Structural
    • Structural Analysis
    • Text
    • Title Text
    Analysis Results
    Analytical Model
    Constraints
    Construction
    Dimensions
    Electrical
    Electrical – Lighting
    Electrical – Loads
    Electrical Engineering
    Energy Analysis
    Fire Protection
    Graphics
    Green Building Properties
    Identiy Data
    IFC Parameters
    Layers
    Materials and Finishes
    Mechanical
    Mechanical – Airflow
    Mechanical – Loads
    Model Properties
    Other
    Phasing
    Photometrics
    Plumbing
    Rebar Set
    Slab Shape Edit
    Structural
    Structural Analysis
    Text
    Title Text

    I’m glad that Revit doesn’t let us customize this list, it would just complicate things even more.  Eric reminds us to “choose a pertinent parameter group for your parameters,” but what does that mean?  Really, it depends on your office.  I would recommend creating a standard.

    I discourage the use of the “Other” category because it ends up being a trash bin holding everything.  “Dimensions” is obvious, but I only put parameters in this group that are relevant to the user of the family.  I use “Analytical Model” for any behind the scenes calculations or dimensions that the user of the model doesn’t need to bother with; unit conversions, dimension calculations to keep the model from breaking, etc.  I have also seen “Model Properties” used for this.  If I have toggles for the visibility of different components I put those under “Construction“, if I have a toggle for something that is graphical only, like in an annotation family, I put that under “Graphics“.

    Tomorrow we will look at using formulas in families.

  • Revit Tip: Easy Wall Poche

    This is the first of what is hopefully many more Revit Tips to come.  Something that I’ve seen in some projects I’ve worked on lately is using filled regions to poché walls and floors in section views.  DON’T DO THIS! Besides taking a large amount of time to initially create, filled regions are not going to update as you add or remove walls, windows, etc.  So how do you poché your walls?  Easy.

    Default Revit Sections Are Flat!
    Default Revit Sections Are Flat!

    There are two tools that you will use to make this happen, Visibility/Graphic Overrides and the Join Tool.

    I think the reason that you would try to used filled regions to poché walls is because you don’t fully understand how Revit displays objects.  Revit uses a hierarchy of graphic settings to determine what to display.

    On the most general level are the project’s Object Styles.  You reach these by going to Manage -> Settings -> Object Styles.  I could write a number of essays on what you can do here, but right now we will just focus on the Walls category.  The main walls category by default has 3 sub-categories.  For these 4 category/sub-categories you can set the line weights/color/pattern for projection and cut views as well as the default material.  This is where we could bump up the line weight for cut walls to make our elevations read clearer.

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