== Basics ==

A fragment of a functional program used to generate coherent noise, probably for purposes related to terrain generation.

Noise expressions can be provided as object literals or built using functions in the built-in <code>noise</code> library.
<code>noise.define_noise_function</code> allows noise expressions to be defined using a shorthand
that's a subset of Lua (see [[#Example definition|example definition]] for an example and its literal equivalent).

== Mandatory properties ==

=== type ===

'''Type''': [[Types/string]]

Name of the type of this expression.
Which other properties apply depend on the expression type.

== Expression types ==

=== variable ===

Reference to a pre-defined variable, constant, or a named noise expression.

Predefined variables include "x", "y", and "distance".

Properties:

* '''variable_name''': a [[Types/string]]

=== function-application ===

Apply a function to a list or associative array of arguments. Some functions expect arguments to be named and some expect them not to be.

Function calls are their own class of expression (as opposed to every function just being its own expression type) because function calls all have similar properties -- arguments are themselves expressions, a function call with all-constant arguments can be constant-folded (due to [[Wikipedia:Referential_transparency|referential transparency]]), etc.

Properties:

* '''function_name''' (a string; see functions, below)
* '''arguments''' (a list or associative array of argument expressions)

=== literal-number ===

Evaluates to the same number every time, given by the '''literal_value''' property.

=== literal-string ===

Evaluates to the same string every time, given by the '''literal_value''' property.

Since the noise generation runtime has no notion of strings or use for them,
this is useful only in constant contexts.

=== literal-object ===

Evaluates to the same object every time, given by the '''literal_value''' property.

e.g.

<syntaxhighlight lang="lua">
{
type = "literal-object",
literal_value = {
name = "Bob Hope",
birth_date = {
year = 1903,
month = 5,
day_of_month = 29
}
}
}
</syntaxhighlight>

Since the noise generation runtime has no notion of objects or use for them,
this is useful only in constant contexts, such as the '''points''' argument
of the '''distance-from-nearest-point''' function.

=== literal-expression ===

Returns the expression represented by its '''literal-value''' property.

== Functions ==

=== add ===

'''Arguments (positional)''': term, other term

Takes 2 positional arguments and adds them.

=== subtract ===

'''Arguments (positional)''': minuend, subtrahend

Takes 2 positional arguments and subtracts the second from the first.

=== multiply ===

'''Arguments (positional)''': factor, other factor

Takes 2 positional arguments and multiplies them.

=== divide ===

'''Arguments (positional)''': dividend, divisor

Takes 2 positional arguments and divides the first by the second.

=== exponentiate ===

'''Arguments (positional)''': base, exponent

Takes 2 positional arguments, and raises the first to the second power.

=== absolute-value ===

'''Arguments (positional)''': value to be absoluted

Takes a single positional argument and returns its absolute value. i.e. If the argument is negative, it is inverted.

=== clamp ===

'''Arguments (positional)''': value to be clamped, lower limit, upper limit

First argument is clamped between the second and third. The second is treated as a lower limit and the third the upper limit.

=== ridge ===

'''Arguments (positional)''': value to be ridged, lower limit, upper limit

Similar to clamp but the input value is folded back across the upper and lower limits
until it lies between them.

=== factorio-basis-noise ===

'''Arguments (named)''':

* '''x'''
* '''y'''
* '''seed0''' - integer between 0 and 4294967295 (inclusive) used to populate the backing random noise
* '''seed1''' - integer between 0 and 255 (inclusive) used to provide extra randomness when sampling
* '''input_scale''' (default: 1) - x and y will be multiplied by this before sampling
* '''output_scale''' (default: 1) - output will be multiplied by this before being returned

Scaling input and output can be accomplished other ways, but are done so commonly
as to be built into this function for performance reasons.

=== factorio-multioctave-noise ===

'''Arguments (named)''':

* '''x'''
* '''y'''
* '''seed0''' - integer between 0 and 4294967295 (inclusive) used to populate the backing random noise
* '''seed1''' - integer between 0 and 255 (inclusive) used to provide extra randomness when sampling
* '''octaves''' - how many layers of noise at different scales to sum
* '''persistence''' (constant) - how strong is each layer compared to the next larger one
* '''input_scale''' (default: 1) - x and y will be multiplied by this before sampling
* '''output_scale''' (default: 1) - output will be multiplied by this before being returned

=== spot-noise ===

Generates random conical spots. The map is divided into square regions, and within each region, candidate points are chosen at random and target density, spot quantity, and radius are calculated for each point (or one of every '''skip_span''' candidate points) by configured expressions. Each spot contributes a quantity to a regional target total (which is the average of sampled target densities times the area of the region) until the total has been reached or a maximum spot count is hit. The output value of the function is the maximum height of any spot at a given point.

The parameters that provide expressions to be evaluated for each point (all named '''something_expression''') need to actually return expression objects.

The quantity of the spot is assumed to be the same as its volume. Since the volume of a cone is '''pi * radius^2 * height / 3''',
the height ('peak value') of any given spot is calculated as '''3 * quantity / (pi * radius^2)'''

'''Arguments (named)''':

* '''x''' (number)
* '''y''' (number)
* '''seed0''' (constant integer) - random seed, part 1 - usually the map seed is used
* '''seed1''' (constant integer) - random seed, part 2 - usually chosen to identify the noise layer
* '''region_size''' (constant integer, default: 512) - width/height of each region
* '''skip_offset''' (constant integer, default: 0) - offset of the first candidate point to use
* '''skip_span''' (constant integer, default: 1) - number of candidate points to skip over after each one used as a spot, including the used one
* '''candidate_point_count''' (constant integer, default:256) - how many candidate points to generate
* '''candidate_spot_count''' (constant integer, default depends on skip_span) - an alternative to candidate_point_count - number of spots to generate: ```candidate_spot_count = X``` is equivalent to '''candidate_point_count / skip_span = X'''
* '''minimum_candidate_point_spacing''' (constant number, default depends on region size) - minimum spacing to *try* to achieve while randomly picking points; spot noise may end up placing spots closer than this in crowded regions
* '''hard_region_target_quantity''' (constant boolean, default: true) - whether to place a hard limit on the total quantity in each region by reducing the size of any spot (which will be the last spot chosen) that would put it over the limit.
* '''density_expression''' (number-returningexpression) - an expression that will be evaluated for each candidate spot to calculate density at that point
* '''spot_quantity_expression''' (number-returningexpression) - an expression that will be evaluated for each candidate spot to calculate the spot's quantity
* '''spot_radius_expression''' (number-returning expression) - an expression that will be evaluated for each candidate spot to calculate the spot's radius (this, together with quantity, will determine the spots peak value)
* '''spot_favorability_expression''' (number-returning expression) - an expression that will be evaluated for each candidate spot to calculate the spot's favorability; spots with higher favorability will be considered first when building the final list of spots for a region

== Example definition ==

To override the 'temperature' named noise expression with one that linearly increases to the southeast:

<syntaxhighlight lang="lua">
local noise = require("noise");

data:extend{
{
type = "noise-expression",
name = "togs-new-temperature-function",
intended_property = "temperature", -- Makes this available in the 'temperature generator' drop-down
expression = noise.define_noise_function( function(x,y,tile,map)
return (x + y) / 1000
end)
}
}
</syntaxhighlight>

Which is equivalent to:

<syntaxhighlight lang="lua">
local noise = require("noise");

data:extend{
{
type = "noise-expression",
name = "temperature",
expression = {
type = "function-application",
function_name = "divide",
arguments = {
{
type = "function-application",
function_name = "add",
arguments = {
{
type = "variable",
variable_name = "x"
},
{
type = "variable",
variable_name = "y"
}
}
},
{
type = "literal-number",
literal_value = 1000
}
}
}
}
}
</syntaxhighlight>

== See also ==

* [https://togos.github.io/togos-example-noise-programs/ A tutorial on authoring noise functions]

Types/NoiseExpression

2019-03-07T16:49:45Z

TOGoS: Even random() is actually referrentially transparent, because it takes x, y as seed, so rephrase about that.

== Basics ==

A fragment of a functional program used to generate coherent noise, probably for purposes related to terrain generation.

Noise expressions can be provided as object literals or built using functions in the built-in <code>noise</code> library.
<code>noise.define_noise_function</code> allows noise expressions to be defined using a shorthand
that's a subset of Lua (see [[#Example definition|example definition]] for an example and its literal equivalent).

== Mandatory properties ==

=== type ===

'''Type''': [[Types/string]]

Name of the type of this expression.
Which other properties apply depend on the expression type.

== Expression types ==

=== variable ===

Reference to a pre-defined variable, constant, or a named noise expression.

Predefined variables include "x", "y", and "distance".

Properties:

* '''variable_name''': a [[Types/string]]

=== function-application ===

Apply a function to a list or associative array of arguments. Some functions expect arguments to be named and some expect them not to be.

Function calls are their own class of expression (as opposed to every function just being its own expression type) because function calls all have similar properties -- arguments are themselves expressions, a function call with all-constant arguments can be constant-folded (due to [[Wikipedia:Referential_transparency|referential transparency]]), etc.

Properties:

* '''function_name''' (a string; see functions, below)
* '''arguments''' (a list or associative array of argument expressions)

=== literal-number ===

Evaluates to the same number every time, given by the '''literal_value''' property.

=== literal-string ===

Evaluates to the same string every time, given by the '''literal_value''' property.

Since the noise generation runtime has no notion of strings or use for them,
this is useful only in constant contexts.

=== literal-object ===

Evaluates to the same object every time, given by the '''literal_value''' property.

e.g.

<syntaxhighlight lang="lua">
{
type = "literal-object",
literal_value = {
name = "Bob Hope",
birth_date = {
year = 1903,
month = 5,
day_of_month = 29
}
}
}
</syntaxhighlight>

Since the noise generation runtime has no notion of objects or use for them,
this is useful only in constant contexts, such as the '''points''' argument
of the '''distance-from-nearest-point''' function.

=== literal-expression ===

Returns the expression represented by its '''literal-value''' property.

== Functions ==

=== add ===

'''Arguments (positional)''': term, other term

Takes 2 positional arguments and adds them.

=== subtract ===

'''Arguments (positional)''': minuend, subtrahend

Takes 2 positional arguments and subtracts the second from the first.

=== multiply ===

'''Arguments (positional)''': factor, other factor

Takes 2 positional arguments and multiplies them.

=== divide ===

'''Arguments (positional)''': dividend, divisor

Takes 2 positional arguments and divides the first by the second.

=== exponentiate ===

'''Arguments (positional)''': base, exponent

Takes 2 positional arguments, and raises the first to the second power.

=== absolute-value ===

'''Arguments (positional)''': value to be absoluted

Takes a single positional argument and returns its absolute value. i.e. If the argument is negative, it is inverted.

=== clamp ===

'''Arguments (positional)''': value to be clamped, lower limit, upper limit

First argument is clamped between the second and third. The second is treated as a lower limit and the third the upper limit.

=== ridge ===

'''Arguments (positional)''': value to be ridged, lower limit, upper limit

Similar to clamp but the input value is folded back across the upper and lower limits
until it lies between them.

=== factorio-basis-noise ===

'''Arguments (named)''':

* '''x'''
* '''y'''
* '''seed0''' - integer between 0 and 4294967295 (inclusive) used to populate the backing random noise
* '''seed1''' - integer between 0 and 255 (inclusive) used to provide extra randomness when sampling
* '''input_scale''' (default: 1) - x and y will be multiplied by this before sampling
* '''output_scale''' (default: 1) - output will be multiplied by this before being returned

Scaling input and output can be accomplished other ways, but are done so commonly
as to be built into this function for performance reasons.

=== factorio-multioctave-noise ===

'''Arguments (named)''':

* '''x'''
* '''y'''
* '''seed0''' - integer between 0 and 4294967295 (inclusive) used to populate the backing random noise
* '''seed1''' - integer between 0 and 255 (inclusive) used to provide extra randomness when sampling
* '''octaves''' - how many layers of noise at different scales to sum
* '''persistence''' (constant) - how strong is each layer compared to the next larger one
* '''input_scale''' (default: 1) - x and y will be multiplied by this before sampling
* '''output_scale''' (default: 1) - output will be multiplied by this before being returned

=== spot-noise ===

Generates random conical spots. The map is divided into square regions, and within each region, candidate points are chosen at random and target density, spot quantity, and radius are calculated for each point (or one of every '''skip_span''' candidate points) by configured expressions. Each spot contributes a quantity to a regional target total (which is the average of sampled target densities times the area of the region) until the total has been reached or a maximum spot count is hit. The output value of the function is the maximum height of any spot at a given point.

The parameters that provide expressions to be evaluated for each point (all named '''something_expression''') need to actually return expression objects.

The quantity of the spot is assumed to be the same as its volume. Since the volume of a cone is '''pi * radius^2 * height / 3</math>,
the height ('peak value') of any given spot is calculated as '''3 * quantity / (pi * radius^2)'''

'''Arguments (named)''':

* '''x''' (number)
* '''y''' (number)
* '''seed0''' (constant integer) - random seed, part 1 - usually the map seed is used
* '''seed1''' (constant integer) - random seed, part 2 - usually chosen to identify the noise layer
* '''region_size''' (constant integer, default: 512) - width/height of each region
* '''skip_offset''' (constant integer, default: 0) - offset of the first candidate point to use
* '''skip_span''' (constant integer, default: 1) - number of candidate points to skip over after each one used as a spot, including the used one
* '''candidate_point_count''' (constant integer, default:256) - how many candidate points to generate
* '''candidate_spot_count''' (constant integer, default depends on skip_span) - an alternative to candidate_point_count - number of spots to generate: ```candidate_spot_count = X``` is equivalent to '''candidate_point_count / skip_span = X'''
* '''minimum_candidate_point_spacing''' (constant number, default depends on region size) - minimum spacing to *try* to achieve while randomly picking points; spot noise may end up placing spots closer than this in crowded regions
* '''hard_region_target_quantity''' (constant boolean, default: true) - whether to place a hard limit on the total quantity in each region by reducing the size of any spot (which will be the last spot chosen) that would put it over the limit.
* '''density_expression''' (number-returningexpression) - an expression that will be evaluated for each candidate spot to calculate density at that point
* '''spot_quantity_expression''' (number-returningexpression) - an expression that will be evaluated for each candidate spot to calculate the spot's quantity
* '''spot_radius_expression''' (number-returning expression) - an expression that will be evaluated for each candidate spot to calculate the spot's radius (this, together with quantity, will determine the spots peak value)
* '''spot_favorability_expression''' (number-returning expression) - an expression that will be evaluated for each candidate spot to calculate the spot's favorability; spots with higher favorability will be considered first when building the final list of spots for a region

== Example definition ==

To override the 'temperature' named noise expression with one that linearly increases to the southeast:

<syntaxhighlight lang="lua">
local noise = require("noise");

data:extend{
{
type = "noise-expression",
name = "togs-new-temperature-function",
intended_property = "temperature", -- Makes this available in the 'temperature generator' drop-down
expression = noise.define_noise_function( function(x,y,tile,map)
return (x + y) / 1000
end)
}
}
</syntaxhighlight>

Which is equivalent to:

<syntaxhighlight lang="lua">
local noise = require("noise");

data:extend{
{
type = "noise-expression",
name = "temperature",
expression = {
type = "function-application",
function_name = "divide",
arguments = {
{
type = "function-application",
function_name = "add",
arguments = {
{
type = "variable",
variable_name = "x"
},
{
type = "variable",
variable_name = "y"
}
}
},
{
type = "literal-number",
literal_value = 1000
}
}
}
}
}
</syntaxhighlight>

== See also ==

* [https://togos.github.io/togos-example-noise-programs/ A tutorial on authoring noise functions]

2019-02-15T02:19:45Z

TOGoS: Show better practice of providing an alternate 'temperature' generator rather than simply overriding the default.

Types/NoiseExpression

2018-09-02T23:18:27Z

TOGoS: Syntax-highlight the literal-object example

Types/NoiseExpression

2018-09-02T21:26:02Z

TOGoS: Don't really need that "e.g." when the section is called 'example'

Types/NoiseExpression

2018-09-02T21:25:28Z

TOGoS: Note and give example of noise.define_noise_function

Types/NoiseExpression

2018-09-01T17:46:50Z

TOGoS: TOGoS moved page User:TOGoS/Types/NoiseExpression to Types/NoiseExpression without leaving a redirect: Now fleshed out enough to be useful!

= Types/NoiseExpression =

== Basics ==

A fragment of a functional program used to generate coherent noise, probably for purposes related to terrain generation.

== Mandatory properties ==

=== type ===

'''Type''': [[Types/string]]

Name of the type of this expression.
Which other properties apply depend on the expression type.

== Expression types ==

=== variable ===

Reference to a pre-defined variable, constant, or a named noise expression.

Predefined variables include "x", "y", and "distance".

Properties:

* '''variable_name''': a [[Types/string]]

=== function-application ===

Apply a function to a list or associative array of arguments.
Some functions expect arguments to be named and some expect them not to be.

Function calls are their own class of expression
(as opposed to every function just being its own expression type)
because function calls all have similar properties --
arguments are themselves expressions,
a call to any pure function (i.e. most functions other than <code>random()</code>)
is [https://en.wikipedia.org/wiki/Referential_transparency referentially transparent]
and can be constant-folded if all of its arguments are constant, etc.

Properties:

* '''function_name''' (a string; see functions, below)
* '''arguments''' (a list or associative array of argument expressions)

=== literal-number ===

Evaluates to the same number every time, given by the '''literal_value''' property.

=== literal-string ===

Evaluates to the same string every time, given by the '''literal_value''' property.

Since the noise generation runtime has no notion of strings or use for them,
this is useful only in constant contexts.

=== literal-object ===

Evaluates to the same object every time, given by the '''literal_value''' property.

e.g.

<pre>
{
type = "literal-object",
literal_value = {
name = "Bob Hope",
birth_date = {
year = 1903,
month = 5,
day_of_month = 29
}
}
}
</pre>

Since the noise generation runtime has no notion of objects or use for them,
this is useful only in constant contexts, such as the '''points''' argument
of the '''distance-from-nearest-point''' function.

== Functions ==

=== add ===

'''Arguments (positional)''': term, other term

Takes 2 positional arguments and adds them.

=== subtract ===

'''Arguments (positional)''': minuend, subtrahend

Takes 2 positional arguments and subtracts the second from the first.

=== multiply ===

'''Arguments (positional)''': factor, other factor

Takes 2 positional arguments and multiplies them.

=== divide ===

'''Arguments (positional)''': dividend, divisor

Takes 2 positional arguments and divides the first by the second.

=== exponentiate ===

'''Arguments (positional)''': base, exponent

Takes 2 positional arguments, and raises the first to the second power.

=== absolute-value ===

'''Arguments (positional)''': value to be absoluted

Takes a single positional argument and returns its absolute value. i.e. If the argument is negative, it is inverted.

=== clamp ===

'''Arguments (positional)''': value to be clamped, lower limit, upper limit

First argument is clamped between the second and third. The second is treated as a lower limit and the third the upper limit.

=== ridge ===

'''Arguments (positional)''': value to be ridged, lower limit, upper limit

Similar to clamp but the input value is folded back across the upper and lower limits
until it lies between them.

=== factorio-basis-noise ===

'''Arguments (named)''':

* '''x'''
* '''y'''
* '''seed0''' - integer between 0 and 4294967295 (inclusive) used to populate the backing random noise
* '''seed1''' - integer between 0 and 255 (inclusive) used to provide extra randomness when sampling
* '''input_scale''' (default: 1) - x and y will be multiplied by this before sampling
* '''output_scale''' (default: 1) - output will be multiplied by this before being returned

Scaling input and output can be accomplished other ways, but are done so commonly
as to be built into this function for performance reasons.

=== factorio-multioctave-noise ===

'''Arguments (named)''':

* '''x'''
* '''y'''
* '''seed0''' - integer between 0 and 4294967295 (inclusive) used to populate the backing random noise
* '''seed1''' - integer between 0 and 255 (inclusive) used to provide extra randomness when sampling
* '''octaves''' - how many layers of noise at different scales to sum
* '''persistence''' (constant) - how strong is each layer compared to the next larger one
* '''input_scale''' (default: 1) - x and y will be multiplied by this before sampling
* '''output_scale''' (default: 1) - output will be multiplied by this before being returned

Types/NoiseExpression

2018-09-01T17:26:53Z

TOGoS: "every time" is 2 words

Types/NoiseExpression

2018-09-01T17:10:49Z

TOGoS: Document noise functions

= Types/NoiseExpression =

== Basics ==

A fragment of a functional program used to generate coherent noise, probably for purposes related to terrain generation.

== Mandatory properties ==

=== type ===

'''Type''': [[Types/string]]

Name of the type of this expression.
Which other properties apply depend on the expression type.

== Expression types ==

=== variable ===

Reference to a pre-defined variable, constant, or a named noise expression.

Predefined variables include "x", "y", and "distance".

Properties:

* '''variable_name''': a [[Types/string]]

=== function-application ===

Apply a function to a list or associative array of arguments.
Some functions expect arguments to be named and some expect them not to be.

Function calls are their own class of expression
(as opposed to every function just being its own expression type)
because function calls all have similar properties --
arguments are themselves expressions,
a call to any pure function (i.e. most functions other than <code>random()</code>)
is [https://en.wikipedia.org/wiki/Referential_transparency referentially transparent]
and can be constant-folded if all of its arguments are constant, etc.

Properties:

* '''function_name''' (a string; see functions, below)
* '''arguments''' (a list or associative array of argument expressions)

=== literal-number ===

Evaluates to the same number every time, given by the '''literal_value''' property.

=== literal-string ===

Evaluates to the same stringevery time, given by the '''literal_value''' property.

Since the noise generation runtime has no notion of strings or use for them,
this is useful only in constant contexts.

=== literal-object ===

Evaluates to the same object every time, given by the '''literal_value''' property.

e.g.

<pre>
{
type = "literal-object",
literal_value = {
name = "Bob Hope",
birth_date = {
year = 1903,
month = 5,
day_of_month = 29
}
}
}
</pre>

Since the noise generation runtime has no notion of objects or use for them,
this is useful only in constant contexts, such as the '''points''' argument
of the '''distance-from-nearest-point''' function.

== Functions ==

=== add ===

'''Arguments (positional)''': term, other term

Takes 2 positional arguments and adds them.

=== subtract ===

'''Arguments (positional)''': minuend, subtrahend

Takes 2 positional arguments and subtracts the second from the first.

=== multiply ===

'''Arguments (positional)''': factor, other factor

Takes 2 positional arguments and multiplies them.

=== divide ===

'''Arguments (positional)''': dividend, divisor

Takes 2 positional arguments and divides the first by the second.

=== exponentiate ===

'''Arguments (positional)''': base, exponent

Takes 2 positional arguments, and raises the first to the second power.

=== absolute-value ===

'''Arguments (positional)''': value to be absoluted

Takes a single positional argument and returns its absolute value. i.e. If the argument is negative, it is inverted.

=== clamp ===

'''Arguments (positional)''': value to be clamped, lower limit, upper limit

First argument is clamped between the second and third. The second is treated as a lower limit and the third the upper limit.

=== ridge ===

'''Arguments (positional)''': value to be ridged, lower limit, upper limit

Similar to clamp but the input value is folded back across the upper and lower limits
until it lies between them.

=== factorio-basis-noise ===

'''Arguments (named)''':

* '''x'''
* '''y'''
* '''seed0''' - integer between 0 and 4294967295 (inclusive) used to populate the backing random noise
* '''seed1''' - integer between 0 and 255 (inclusive) used to provide extra randomness when sampling
* '''input_scale''' (default: 1) - x and y will be multiplied by this before sampling
* '''output_scale''' (default: 1) - output will be multiplied by this before being returned

Scaling input and output can be accomplished other ways, but are done so commonly
as to be built into this function for performance reasons.

=== factorio-multioctave-noise ===

'''Arguments (named)''':

* '''x'''
* '''y'''
* '''seed0''' - integer between 0 and 4294967295 (inclusive) used to populate the backing random noise
* '''seed1''' - integer between 0 and 255 (inclusive) used to provide extra randomness when sampling
* '''octaves''' - how many layers of noise at different scales to sum
* '''persistence''' (constant) - how strong is each layer compared to the next larger one
* '''input_scale''' (default: 1) - x and y will be multiplied by this before sampling
* '''output_scale''' (default: 1) - output will be multiplied by this before being returned

Types/NoiseExpression

2018-09-01T16:28:29Z

TOGoS: Move from User:TOGoS

= Types/NoiseExpression =

== Basics ==

A fragment of a functional program used to generate coherent noise, probably for purposes related to terrain generation.

== Mandatory properties ==

=== type ===

'''Type''': [[Types/string]]

Name of the type of this expression.
Which other properties apply depend on the expression type.

== Expression types ==

=== variable ===

Reference to a pre-defined variable, constant, or a named noise expression.

Predefined variables include "x", "y", and "distance".

Properties:

* '''variable_name''': a [[Types/string]]

=== function-application ===

Apply a function to a list or associative array of arguments.
Some functions expect arguments to be named and some expect them not to be.

Function calls are their own class of expression
(as opposed to every function just being its own expression type)
because function calls all have similar properties --
arguments are themselves expressions,
a call to any pure function (i.e. most functions other than <code>random()</code>)
is [https://en.wikipedia.org/wiki/Referential_transparency referentially transparent]
and can be constant-folded if all of its arguments are constant, etc.

Properties:

* '''function_name''' (a string; see functions, below)
* '''arguments''' (a list or associative array of argument expressions)

=== literal-number ===

Evaluates to the same number every time, given by the '''literal_value''' property.

=== literal-string ===

Evaluates to the same stringevery time, given by the '''literal_value''' property.

Since the noise generation runtime has no notion of strings or use for them,
this is useful only in constant contexts.

=== literal-object ===

Evaluates to the same object every time, given by the '''literal_value''' property.

e.g.

<pre>
{
type = "literal-object",
literal_value = {
name = "Bob Hope",
birth_date = {
year = 1903,
month = 5,
day_of_month = 29
}
}
}
</pre>

Since the noise generation runtime has no notion of objects or use for them,
this is useful only in constant contexts, such as the '''points''' argument
of the '''distance-from-nearest-point''' function.

== Functions ==

=== add ===

'''Arguments (positional)''': term, other term

Takes 2 positional arguments and adds them.

=== subtract ===

'''Arguments (positional)''': minuend, subtrahend

Takes 2 positional arguments and subtracts the second from the first.

=== multiply ===

'''Arguments (positional)''': factor, other factor

Takes 2 positional arguments and multiplies them.

=== divide ===

'''Arguments (positional)''': dividend, divisor

Takes 2 positional arguments and divides the first by the second.

=== exponentiate ===

'''Arguments (positional)''': base, exponent

Takes 2 positional arguments, and raises the first to the second power.

=== absolute-value ===

'''Arguments (positional)''': value to be absoluted

Takes a single positional argument and returns its absolute value. i.e. If the argument is negative, it is inverted.

=== clamp ===

'''Arguments (positional)''': value to be clamped, lower limit, upper limit

First argument is clamped between the second and third. The second is treated as a lower limit and the third the upper limit.

=== ridge ===

'''Arguments (positional)''': value to be ridged, lower limit, upper limit

Similar to clamp but the input value is folded back across the upper and lower limits
until it lies between them.

=== factorio-basis-noise ===
=== factorio-multioctave-noise ===

User:TOGoS

2018-09-01T16:28:16Z

TOGoS: Remove noise expressions

Hi, I'm TOGoS! I'm mostly trying to open up the terrain generation so that it can be hacked on (by staff or modders) without having to embed oneself in the C++ guts of factorio for several weeks.

User:TOGoS

2018-09-01T16:27:35Z

TOGoS: /* Functions */

Hi, I'm TOGoS! I'm mostly trying to open up the terrain generation so that it can be hacked on (by staff or modders) without having to embed oneself in the C++ guts of factorio for several weeks.

= Types/NoiseExpression =

== Basics ==

A fragment of a functional program used to generate coherent noise, probably for purposes related to terrain generation.

== Mandatory properties ==

=== type ===

'''Type''': [[Types/string]]

Name of the type of this expression.
Which other properties apply depend on the expression type.

== Expression types ==

=== variable ===

Reference to a pre-defined variable, constant, or a named noise expression.

Predefined variables include "x", "y", and "distance".

Properties:

* '''variable_name''': a [[Types/string]]

=== function-application ===

Apply a function to a list or associative array of arguments.
Some functions expect arguments to be named and some expect them not to be.

Function calls are their own class of expression
(as opposed to every function just being its own expression type)
because function calls all have similar properties --
arguments are themselves expressions,
a call to any pure function (i.e. most functions other than <code>random()</code>)
is [https://en.wikipedia.org/wiki/Referential_transparency referentially transparent]
and can be constant-folded if all of its arguments are constant, etc.

Properties:

* '''function_name''' (a string; see functions, below)
* '''arguments''' (a list or associative array of argument expressions)

=== literal-number ===

Evaluates to the same number every time, given by the '''literal_value''' property.

=== literal-string ===

Evaluates to the same stringevery time, given by the '''literal_value''' property.

Since the noise generation runtime has no notion of strings or use for them,
this is useful only in constant contexts.

=== literal-object ===

Evaluates to the same object every time, given by the '''literal_value''' property.

e.g.

<pre>
{
type = "literal-object",
literal_value = {
name = "Bob Hope",
birth_date = {
year = 1903,
month = 5,
day_of_month = 29
}
}
}
</pre>

Since the noise generation runtime has no notion of objects or use for them,
this is useful only in constant contexts, such as the '''points''' argument
of the '''distance-from-nearest-point''' function.

== Functions ==

=== add ===

'''Arguments (positional)''': term, other term

Takes 2 positional arguments and adds them.

=== subtract ===

'''Arguments (positional)''': minuend, subtrahend

Takes 2 positional arguments and subtracts the second from the first.

=== multiply ===

'''Arguments (positional)''': factor, other factor

Takes 2 positional arguments and multiplies them.

=== divide ===

'''Arguments (positional)''': dividend, divisor

Takes 2 positional arguments and divides the first by the second.

=== exponentiate ===

'''Arguments (positional)''': base, exponent

Takes 2 positional arguments, and raises the first to the second power.

=== absolute-value ===

'''Arguments (positional)''': value to be absoluted

Takes a single positional argument and returns its absolute value. i.e. If the argument is negative, it is inverted.

=== clamp ===

'''Arguments (positional)''': value to be clamped, lower limit, upper limit

First argument is clamped between the second and third. The second is treated as a lower limit and the third the upper limit.

=== ridge ===

'''Arguments (positional)''': value to be ridged, lower limit, upper limit

Similar to clamp but the input value is folded back across the upper and lower limits
until it lies between them.

=== factorio-basis-noise ===
=== factorio-multioctave-noise ===

User:TOGoS

2018-09-01T16:07:29Z

TOGoS: Move noise expression work to my user page

Prototype/NamedNoiseExpression

2018-08-29T02:38:59Z

TOGoS: Types/NoiseExpression

== Basics ==

A [[Types/NoiseExpression]] together with a name.

Named noise expressions are used to specify functions for elevation, temperature, moisture, aux, and cliffiness.

In 0.16 the 'name' of the NamedNoiseExpression must be "default-<property>", e.g. "default-elevation"
for it to be picked up by the terrain generation system and used to calculate elevation.

== Mandatory properties ==

=== name ===
'''Type''': [[Types/string]]

Name of this expression, e.g. "default-temperature".

=== expression ===
'''Type''': [[Types/NoiseExpression]]

The expression itself.

Prototype/NamedNoiseExpression

2018-08-29T02:38:34Z

TOGoS: Types/NoiseExpression

== Basics ==

A [[Types/NoiseExpreession]] together with a name.

Named noise expressions are used to specify functions for elevation, temperature, moisture, aux, and cliffiness.

In 0.16 the 'name' of the NamedNoiseExpression must be "default-<property>", e.g. "default-elevation"
for it to be picked up by the terrain generation system and used to calculate elevation.

== Mandatory properties ==

=== name ===
'''Type''': [[Types/string]]

Name of this expression, e.g. "default-temperature".

=== expression ===
'''Type''': [[Types/NoiseExpression]]

The expression itself.

Prototype/NamedNoiseExpression

2018-08-29T02:37:26Z

TOGoS: Created page with "== Basics == A NoiseExpreession together with a name. Named noise expressions are used to specify functions for elevation, temperature, moisture, aux, and cliffiness. I..."

== Basics ==

A [[NoiseExpreession]] together with a name.

Named noise expressions are used to specify functions for elevation, temperature, moisture, aux, and cliffiness.

In 0.16 the 'name' of the NamedNoiseExpression must be "default-<property>", e.g. "default-elevation"
for it to be picked up by the terrain generation system and used to calculate elevation.

== Mandatory properties ==

=== name ===
'''Type''': [[Types/string]]

Name of this expression, e.g. "default-temperature".

=== expression ===
'''Type''': [[Types/NoiseExpression]]

The expression itself.