Revt families cheat sheet

REVIT FAMILIES CHEAT SHEET Formula Syntax, Geometric Relationships, & Tricks

REVIT FAMILIES CHEAT SHEET Formula Syntax, Geometric Relationships, & Tricks +

Addition

Adds values together

-

Subtraction

Subtracts one value from another

*

Multiplication

Multiplies values together

/

Division

Divides one value from another

^

Exponentiation

Raises a value to another

sqrt(x)

Square Root

Finds the square root of a value

sin(x)

Sine

Finds the sine of an angle

cos(x)

Cosine

Finds the cosine of an angle

tan(x)

Tangent

Finds the tangent of an angle

asin(x)

Arcsine

Finds the inverse sine of a value

acos(x)

Arccosine

Finds the inverse cosine of a value

atan(x)

Arctangent

Finds the inverse tangent of a value

pi()

π Pi

Mathematical constant π

exp(x)

e Raised to an exponent

Mathematical constant e raised to the x power

ln(x)

Natural Logarithm

Logarithm of a number to the base value of mathematical constant e

log(x)

Logarithm

The power to which a fixed number (the base) must be raised to produce a given number. A base of 10 is assumed

abs(x)

Absolute value

The magnitude of a real number without regard to its sign

round(x)

Round

Rounds a value to the nearest whole number

roundup(x)

Round up

Rounds a value to a whole number grater than or equal to the value

rounddown(x) Round down

Rounds a value to a whole number less than or equal to the value

if(x,y,z)

Conditional statement

Gives different values based on whether a given condition is true or false: If(condition, result if condition is true, result if condition is false). When you have a yes/no parameter, the true and false results are implied. You do not use the IF(x,y,z) formula, you simply write the condition. If the condition is true, the box is checked, if false, the box is unchecked

and(a,b,c,…)

And statement

Two or more conditions must all be true: AND(condition 1, condition 2, condition3, etc.)

or(a,b,c,…)

Or statement

One of two or more conditions must be true: OR(condition 1, condition 2, condition3, etc.)

not(a,b,c,…)

Not statement

Two or more conditions must all be false: NOT(condition 1, condition 2, condition3, etc.)

=

Equal

Compares equal values

<

Less than

Compares value which is less than another

>

Greater than

Compares value which is greater than another

not(a>b)

Less than or equal

Compares value which is less than or equal to another. Revit does not have a ≤ function, so this is how to accomplish the same logic

not(a<b)

Greater than or equal

Compares value which is greater than or equal to another. Revit does not have a ≥ function, so this is how to accomplish the same logic

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REVIT FAMILIES CHEAT SHEET Formula Syntax, Geometric Relationships, & Tricks This same logic can be used to return the greatest of more than three variables, but with each variable you can see how it will get more complicated.

Returning a string You can use if statements to return a text value (string) based on a condition, simply us quotation marks around the text to indicate a string: Text Parameter = if(Area<100, “Non-Rentable”, “Rentable”) Circle (x-h)^2+(y-k)^2=r^2 Circular Area pi()*r^2 Circumference 2*pi()*r

Ellipse ((x-h)^2/a^2)+((y-k)^2/b^2)=1 Elliptical Area pi()*a*b Triangular Area (b*h)/2

Useful Tricks Nesting if formulas Placing one or more if statements into another if statement allows you to have more than one condition.

For example, you want to calculate total rent generated by an area, but different square footage ranges have different rental rates: Given:

Restrict user inputs to a range Sometimes you want to build in logic to keep a user from breaking the model by entering in a value that does not make sense or that may prevent your family from working properly: Given: a = Minimum acceptable value b = Maximum acceptable value Value = Parameter set by end user but not assigned as a constraint ActualValue = Restricted parameter which is assigned as a constraint Then: ActualValue = if (Value < a, a, if (Value > b, b, Value))

ft2

$25/ft2

0-49 rents at 50-149 ft2 rents at $22/ft2 150 ft2 or more rents at $20/ft2 Then: TotalRent = if(Area < 50, Area/1 * 25, if(Area <150, Area/1 * 22, Area/1 * 20)) *Notice that the Area is divided by 1. This is to neutralize the ft2 unit. If this is not done, you will get an error. See the Inconsistent Units Error section for more details.

Returning the greatest of three variables Given the following three variables, they could be lengths, numbers, areas, etc.: a, b, & c Then:

Round x to the nearest multiple of y Sometimes it is not enough to round to the nearest whole number. If you would like to round to the nearest multiple of a number use the round function with a little math: = (round(x/y))*y Round 23 to nearest multiple of 5 = (round(23/5)) * 5 = 25 Locking a yes/no parameter Sometimes you want to lock a yes/no parameter so that the end user can’t change it: Lock Checked = 1 < 2 Lock Unchecked = 1 > 2

Greatest = if(if(a > b, a, b) > c, if(a > b, a, b), c)

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REVIT FAMILIES CHEAT SHEET Formula Syntax, Geometric Relationships, & Tricks In other situations, you may not have enough units. Say you have a length or area parameter, and you are trying to define it by multiplying two or more number parameters together, which do not have units, you will also get the Inconsistent Units Error:

Correcting Inconsistent Units Error This error occurs for two main reasons: Reason 1 – The equation you entered does not yield a value in the same units as the parameter type. In other words, you have not considered the units for all the variables in your equation.

For example, recall that Length x Length = Area This means that if you have a length parameter, and you are trying to define it by multiplying two or more length parameters together, you will get the Inconsistent Units Error: Length Param. = Length1 x Length2 = Area Length Param. = 10ft x 20ft = 200ft2

Error Error

Length Param. = Length1 x Length2 x Length3 = Volume Length Param. = 10ft x 20ft x 30ft = 6,000ft3

Error Error

It can also happen that your formula may contain parameters with differing units. In the case of calculating a total cost (a currency parameter) which you are trying to define by multiplying a room area by a square foot cost, you will get the Inconsistent Units Error: Currency Param. = Area x Cost = Mixed Units Currency Param. = 250ft2 x $120 = $30,000ft2

Error Error

To correct these types of errors, you must remove the inappropriate units from one of your parameters so that the equation yields the correct units for the parameter type. This is often accomplished by dividing one or more of the parameters by 1: Length Param. = Length1 x (Length2/1) = Length Length Param. = 10ft x (20ft/1ft) = 200ft

Length Param. = Number1 x Number2 = No Units Length Param. = 10 x 20 = 200

Error Error

Area Param. = Number1 x Number2 = No Units Area Param. = 10 x 20 = 200

Error Error

In this type of situation, you must add the appropriate unit to one or more of your parameters so that the equation yields the correct units for the parameter type. This is often accomplished by multiplying parameters by 1: Length Param. = Number1 x Number2 x 1 = Length Length Param. = 10 x 20 x 1ft = 200ft

No Error No Error

Area Param. = Number1 x 1 x Number2 x 1 = Area Area Param. = 10 x 1ft x 20 x 1ft = 200ft2

No Error No Error

Reason 2 – Part or all your equation is not appropriate for the parameter.

For example, you have a Yes/No parameter but you have not entered a condition statement. Maybe you have a Text parameter but your equation yields a number.

There are other possibilities, but you get the idea; something about your equation does not agree with the parameter’s logic.

You can solve this error by simply checking your parameter type, and reviewing your equation for inappropriate variables, typos, or characters which do not belong given the type of parameter.

No Error No Error

Length Param. = Length1 x (Length2/1) x (Length3/1) = Length No Error Length Param. = 10ft x (20ft/1ft) x (30ft/1ft) = 6,000ft No Error Currency Param. = (Area/1) x Cost = Cost Currency Param. = (250ft2/1ft2) x $120 = $30,000

No Error No Error

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REVIT FAMILIES CHEAT SHEET Formula Syntax, Geometric Relationships, & Tricks Circular Segments Relationship Equation Lookup Chart What you want to find

What you know

s

c

a

r

h

d

(1/2)*c*(1/sin((pi()*a)/360))

(1/2)*c*(CSC((pi()*a)/360)-COT((pi()*a)/360))

(1/2)*c*(1/tan((pi()*a)/360))

r-(sqrt(r^2-(c^2/4)))

(1/2)*r*sqrt(4-(c^2/r^2))

ca

(1/360)*pi()*a*c*(1/sin((pi()*a)/360))

cr

2*r*asin(c/(2*r))

(360/pi())*asin(c/(2*r))

ch

asin(c/(h+(c^2/(4*h))))*(h+(c^2/(4*h)))

(360*asin((4*c*h)/(c^2+4*h^2)))/pi()

(h/2)+(c^2/(8*h))

cd

d*sqrt((c^2/d^2)+4)*atan(c/(2*d))

(360/pi())*atan(c/(2*d))

(1/2)*d*sqrt(c^2/d^2+4)

ar

(a/180)*pi()*r

2*r*sin((pi()*a)/360)

ah

-((pi()*a*h)/(180*(cos((pi()*a)/360)-1)))

2*(-(h/(cos((pi()*a)/360)-1)))*sin((pi()*a)/360)

-(h/(cos((pi()*a)/360)-1))

ad

(1/180)*pi()*a*d*(1/cos((pi()*a)/360))

2*d*tan((pi()*a)/360)

d*(1/cos((pi()*a)/360))

rh

2*r*acos(1-(h/r))

2*sqrt(-h*(h-2*r))

(360/pi())*acos(1-(h/r))

rd

2*r*acos(1-(d/r))

2*sqrt(r^2-d^2)

(360/pi())*acos(d/r)

hd

2*(d+h)*acos(d/(d+h))

2*sqrt(h*(2*d+h))

(360*acos(d/(d+h)))/pi()

(sqrt((c^2-4*h^2)^2/(c^2+4*h^2)^2)*(c^2+4*h^2))/(8*h) sqrt(d^2+((1/2)*c)^2)-d r*(1-cos((pi()*a)/360))

r*cos((pi()*a)/360) -(h/(cos((pi()*a)/360)-1))-h

d*((1/cos((pi()*a)/360))-1) r-h r-d

h+d

Right Triangle Relationship Equation Lookup Chart What you want to find a

b

What you know

ab

c

A

B

sqrt(a^2+b^2)

atan(a/b)

atan(b/a)

asin(a/c)

acos(a/c)

ac

sqrt(c^2-a^2)

aA

a/tan(A)

a/sin(A)

aB

a*tan(b)

a/cos(B)

bA

sqrt(c^2b^2) b*tan(A)

b/cos(A)

bB

b/tan(B)

b/sin(B)

cA

c*sin(A)

c*cos(A)

cB

c*cos(B)

c*sin(B)

bc

90-A 90-B acos(b/c)

asin(b/c) 90-A

90-B 90-A 90-B

Right Triangle

Circular Segment

You can download an excel version of these charts for easy copy and pasting here.

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