Expression Modifier

Expression

With the Expression Channel Modifier you use various mathematical and logical operators to define an output value based on input values. Expressions are especially useful in creating complex animations that don't require keyframes, and they are easy to adjust and update. The Expression modifier uses the muParser expression engine.

Input A/Input B/Input C/Input D: These are the user-defined input variables. Each is a floating-point value and is referred to in an expression by its variable name: A, B, C, or D.

Expression: This is the expression that Modo executes based on the defined inputs. For example, A passes the value coming in on the Input A channel to the output channel, or C+D adds the values coming in on the Input C and Input D channels and sets the sum to the output channel. You can also use built-in functions. For example, sin(A) outputs the sine value of Input A to the output. You can also use conditional statements. For example, with A>B?C:D Modo sends the value in Input C to the output if Input A is greater than Input B; if not, Modo sends the value in Input D.

Output: The output value is the value returned by the user-defined expression.

Built-in Functions

By default, Modo with the muParser expression engine includes the following functions. The table lists the function names and a brief description of each with the number of arguments, if applicable.

Name	Meaning
sin	sine function
cos	cosine function
tan	tangens function
asin	arcus sine function
acos	arcus cosine function
atan	arcus tangens function
sinh	hyperbolic sine function
cosh	hyperbolic cosine
tanh	hyperbolic tangens function
asinh	hyperbolic arcus sine function
acosh	hyperbolic arcus tangens function
atanh	hyperbolic arcur tangens function
log2	logarithm to the base 2
log10	logarithm to the base 10
log	logarithm to the base 10
ln	logarithm to base e (2.71828...)
exp	e raised to the power of x
sqrt	square root of a value
sign	-1 if x is less than 0; 1 if x greater than 0
rint	round to nearest integer
abs	absolute value
min	min of all arguments
max	max of all arguments
sum	sum of all arguments
avg	mean value of all arguments
noise	noise value takes 1-3 arguments
floor(x)	gives the integer value of x (For example, 3.5 becomes 3.)
ceil(x)	rounds up to the next integer value of x (For example, 3.5 becomes 4.)
mod(a,b)	returns the remainder of a divided by b
clamp(a, min, max)	given a value a, if a is less then min, min is returned. If greater then max, max is returned. If in between min and max, a is returned.

Built-in Binary Operators

By default, Modo with the muParser expression engine includes the following binary operators. The table lists the operator, a brief description, and the priority assigned to each operator.

Operator	Meaning	Priority
=	assignment *	-1
&&	logical and	1
||	logical or	2
< =	less or equal	4
>=	greater or equal	4
!=	not equal	4
==	equal	4
>	greater than	4
<	less than	4
+	addition	5
-	subtraction	5
*	multiplication	6
/	division	6
^	raise x to the power of y	7

*The assignment operator is special because it changes one of its arguments. You can only apply it to variables.

Other Operators

The muParser expression engine has built-in support for the if/then/else operator. It uses a 'lazy' evaluation to make sure only the necessary branch of the expression is evaluated.

Operator	Meaning	Remarks
?:	if then else operator	C/C++ style syntax