# OpenSCAD User Manual/The OpenSCAD Language/Fast Guide(c.t.chin)

Jump to navigation Jump to search

# Objects

## Primitives

### Primitive Solids

OpenSCAD provides four 3D primitive solids: cube(), sphere(), cylinder(), and polyhedron(). Note that surface() and import() may also be considered as primitive solids.

### Primitive Shapes

OpenSCAD provides four 2D primitive shapes: square(), circle(), polygon(), and text().

## Flow Control

### if() ... else ...

 Conditional Object if (expr_Q) object_T; Conditional Object if (expr_Q) object_T; else object_F;

The conditional object performs a test (evaluates the query expr_Q), and renders either object_T or object_F depending on the truth value of the test result. If object_F was to be nothing, then the else object_F; portion is optional.

More commonly, the compound statement form of if() is used, as exemplified by:

if (a1 > a2) {
// stack cube(a2) on top of cube(a1)
cube(a1);
translate([0,0,a1]) cube(a2);
} else {
// stack cube(a1) on top of cube(a2)
cube(a2);
translate([0,0,a2]) cube(a1);
}

If the result of the conditional evaluation is not an object, but a quantity, use the ? : conditional operator.

While it is allowed to assign variables in the compound form, the scope of those variables is limited to the curly brackets.

a = 5;
translate([0,0,0]) sphere(a);
if (a > 0) {
echo("Let's change!  a = ", a);
translate([20,0,0]) sphere(a);
a = 10;
}
echo("We don't forget!  a = ", a);

The outcome is a small and a large sphere, and in the console:

ECHO: "Let's change!  a = ", 10
ECHO: "We don't forget!  a = ", 5

Note that "a is 10" within the scope of the curly bracket, the corresponding statement a = 10; need not precede the echo() and sphere() statements for its effect to apply. After the if() statement, the assignment to a is lost, so we "recall" a is still 5. See Scope of variables for more details.

Nested if

Since a complete if() statement is an object, it can be nested in another if() statement. A common form is multiply nested "else if" statements:

if (a > 100) {
echo("HUGE!");
sphere(a);
// etc...
} else if (a > 10) {
echo("big.");
translate([0,0,10]) sphere(a);
// etc...
} else if (a > 1) {
echo("not so big...");
color("red") sphere(a);
} else {
echo("Sorry, I lost it.");
}

import()

surface()

echo()

# Operators

## Arithmetic Operators

The scalar arithmetical operators take numbers as operands and produce a new number.

 + add - subtract - negate (unary) * multiply / divide % modulo

## Conditional Operator ? :

 Conditional Operator expr_Q ? expr_T : expr_F

An operator which returns either of two expressions depending on the truth value of a query expression. For example:

var = expr_Q ? expr_T : expr_F;

The expression expr_Q is evaluated and if it's true, expr_T is evaluated and assigned to var; otherwise expr_F is evaluated and assigned to var. If expr_Q evaluated to a non-Boolean result, it is converted to Boolean; see here.

The conditional operator is essential when creating a recursive function call, because it is used to terminate the recursion; see here.

The conditional operator can be used like a nested if also, as in the following example:

 NSides = (FF=="triangular") ? 3 : (FF=="hexagonal") ? 6 (FF=="octagonal") ? 8 : (FF=="circular") ? 180 : 0;

# Functions

## Math Functions

### Trigonometric Functions

The trigonometric functions use the C Language mathematics library functions. Remember all numbers in OpenSCAD are IEEE double floating points. A good reference for the specifics of the C math library are (math.h) and (acos) at the Open Group website. For a quick reference to the relevant mathematics, see Trigonometric functions.

Note that the trigonometric functions do not work on vectors. Invalid inputs produce nan (e.g. acos(2)) or undef (e.g. sin("2")).

Function Description Notes
sin(x) trigonometric sine of x -inf < x < inf is in degrees, return value in [-1,+1]
cos(x) trigonometric cosine of x -inf < x < inf is in degrees, return value in [-1,+1]
tan(x) trigonometric tangent of x -inf < x < inf is in degrees, return value in (-inf, inf)
asin(x) inverse sine of x -1 <= x <= 1, return value in [-90,+90] (degrees)
acos(x) inverse cosine of x -1 <= x <= 1, return value in [0,+180] (degrees)
atan(x) inverse tangent of x -inf <= x <= inf, return value in [-90,+90] (degrees)
atan2(y, x) inverse tangent of y/x -inf <= x,y <= inf, return value in [-180,+180] (degrees) see also: atan2

More precisely the return value is the angle between the line joining origin to the point (x,y) and the X-axis

### Real Functions

Real functions require numeric inputs and produce numbers, except for rands() which returns a vector of numbers.

Function Description Notes
abs(x) absolute value of x -inf < x < inf, return value in [0,+inf)
sign(x) sign of x, see also Sign function -inf < x < inf, return value is 1, 0, or -1, if x is greater than, equal to, or less than 0
ceil(x) ceiling (integer) of real number x, see also: Ceil Function -inf < x < inf, return value is the smallest integer not less than x

also known as rounding off a number towards +inf

floor(x) floor (integer) of real number x, see also: Floor Function -inf < x < inf, return value is the largest integer not greater than x

also known as rounding off a number towards -inf

round(x) rounding function of real number x -inf < x < inf, return value is the integer nearest to x
pow(x,y) x raised to the power of y, i.e. ${\displaystyle x^{y}}$ -inf < x,y < inf
sqrt(x) square root of x, i.e. ${\displaystyle {\sqrt {x}}}$ 0 <= x < inf, return value is the integer nearest to x, if x is negative, returns nan
exp(x) exponential function of x, i.e. ${\displaystyle e^{x}}$, see also: Exponent -inf < x < inf
ln(x) natural logarithm of x, i.e. ${\displaystyle \ln x=\log _{e}x}$, see also: Natural logarithm 0 <= x < inf, if x is negative, returns nan
log(x) logarithm (base 10) of x, i.e. ${\displaystyle \log x=\log _{10}x}$, see also: Logarithm 0 <= x < inf, if x is negative, returns nan
rands(a,b,n) pseudo random number generator, see the main article return a vector with n random numbers in the range [a, b]

Some examples:

echo(ceil(4.4),ceil(-4.4));      // ECHO: 5, -4
echo(floor(4.4),floor(-4.4));    // ECHO: 4, -5
echo(exp(1),exp(ln(3)*4));       // ECHO: 2.71828, 81
sign(-5.0); // ECHO -1
sign(0);// ECHO 0
sign(8.0);// ECHO 1
round(5.4); //-> 5
round(5.5); //-> 6
round(5.6); //-> 6
round(-5.4); //-> -5
round(-5.5); //-> -6
round(-5.6); //-> -6


### Pseudo Random number generator

Generates a vector of pseudo random numbers. In order to generate a single random value as a number, instead of a vector of length 1, use x = rands(a,b,1)[0];. A seed value can be supplied optionally. From the moment a seed value is given, the sequence of pseudo random numbers being generated is deterministic. This provide a convenient way to debug the program using a constant seed value between repeated execution of the program.

Parameters

min_value
Minimum value of random number range
max_value
Maximum value of random number range
value_count
Number of random numbers to return as a vector
seed_value (optional)
Seed value for random number generator for repeatable results. On versions before late 2015, seed_value gets rounded to the nearest integer

Usage Examples:

// get a single number
vec_rand = rands(0,10,1);
single_rand = rands(0,10,1)[0];
echo(vec_rand);    // ECHO: [4.44795]
echo(single_rand); // ECHO: 7.86455

// get a vector of 4 random numbers with seed value 42
random_vect=rands(5,15,4,42);
echo(random_vect); // ECHO: [8.7454, 12.9654, 14.5071, 6.83435]


cross, norm

max, min

len, concat

lookup

search()

str(), chr()

search()

dxf_cross()

dxf_dim()

parent_module(n)

# Functions and Module Definitions

## Function Definition

function name(param_list) = expr;

Note that inside a function definition, variables defined in the main scope is accessible. See variables and scopes.

### Recursive function calls

Recursive function calls are supported. Using the Conditional Operator it's possible to ensure the recursion is terminated. Note: There is a built-in recursion limit to prevent an application crash. If the limit is hit, the function returns undef.

example
 // recursion - find the sum of the values in a vector (array) by calling itself
// from the start (or s'th element) to the i'th element - remember elements are zero based

function sumv(v,i,s=0) = (i==s ? v[i] : v[i] + sumv(v,i-1,s));

vec=[ 10, 20, 30, 40 ];
echo("sum vec=", sumv(vec,2,1)); // calculates 20+30=50


include <>

use <>

# Special Variables

$t$fn etc

$vpn etc$parent_modules

# Modifiers

A modifier, when preceding an object, modifies the behavior of the interpreter during preview and rendering for that object or all other objects in the program. They are essential aids to the user when designing even a minimally complicated object.