Slic3r Manual


Conditional G-code is a powerful feature of Slic3r that allows for arbitrary math to be done in Custom G-code fields as well as setting conditions for specific statements to appear in output from Custom G-code.

Conditional expressions

Conditional expressions has the following syntax:

expression may take one of the following forms:

subexpression has the same forms as expression.

If _subexpression_s exist, they are evaluated before any other operators.

Available operators:

The true and false keywords are available.

To apply a single condition to multiple lines, repeat it once for each line:

{if [layer_num] == 10}M104 S210
{if [layer_num] == 10}M600

If a conditional expression evaluates to false, all the characters until the end of the line are removed. If a conditional expression fails to parse, it's silently left untouched.

Expressions may be chained for an implicit AND:

{if [layer_num] == 10}{if [temperature_1] != 210}M104 S210


Value expressions (G-code Math)

Any expression enclosed in two curly brackets, but not starting with {if is evaluated as an arithmetic expression: {foo - bar}. If evaluation fails, the expression is silently left untouched. If any float variables are used, return value will have decimals. If string variables are mixed with numeric variables, they are parsed as floats if they have a dot, or integers otherwise.

Value expressions can be used in conditional expressions by nesting them: {if {foo - bar} > 10}.