# Tychos Python Language Reference

The following reference guide identifies the language syntax, built in variables, functions, and classes that are used to code your simulations using the Python Language. We have included documentation here for some of the helpful functions defined in the Python language. This is not a complete list of all functions available in Python, just ones that might be commonly used in Tychos for building scenarios as well as defining goals for those scenarios.

Comments are statements that you can insert in your code that do not get interpreted and executed by Tychos. To create a comment, you simply indicate a comment by using a hashtag:
# This is a comment.

## Variables

To define a variable in Tychos all you need to do is identify a name for the variable. You then type an `=` sign to assign a value to the variable. The following demonstrates various variable declarations
# Assigns a variable called x the value of 10
x = 10
# Assign a new variable y the value of the x
y = x
# Assign x the value of itself plus 1
x = x + 1

## Built-in Scenario Variables

There are a few variables that are built into Tychos. These variables are:
• `t` — How many seconds has passed since this Scenario was started?
• `dt` — Time between frames as seconds, e.g. 0.1 is 1/10th of a second.
• `frame_count` — How many frames have passed? e.g. 1, 2, 3...

## Common Math Operators and Functions

These are some common mathematical operators and functions for performing various calculations.

### Mathematical Operators

Tychos uses the following operators to perform basic math calculations:
• `+` — Addition
• `-` — Subtraction
• `*` - Multiplication
• `/` - Division
• ** - Exponent
• `%` - Modulo

### Basic Math Functions

You can also use the following basic math functions:

#### sqrt(positive_number)

The `sqrt(positive_number)` function takes a single non negative number and returns the real square root of the number.
# returns number 2
sqrt(4)

#### exp(power)

The `exp(power)` function calculates Euler's number (e) to the given power.
# returns 54.59815
exp(4)

#### log(x)

The `log(x)` returns the natural log (base e) of x.
# returns number 2
abs(-2)

#### ceil(x)

The `ceil(x)` function rounds a number up to the nearest integer.
# returns 5
exp(4.1)

#### floor(x)

The `floor(x)` function rounds a number down to the nearest integer.
# returns 4
exp(4.9)

#### sign(x)

The `sign(x)` function returns +1 if x is less than 0, -1 if x is greater than 0, and 0 if x is equal to 0.
# returns -1
sign(-42)
# returns 1
sign(42)
# returns 0
sign(0)

#### abs(x)

The `abs(x)` function returns the absolute value of a number.
# returns number 2
abs(-2)

#### random()

The `random()` function returns a semi random number between 0 and 1.
x = random()
randrange(a, b)
The `randrange(a,b)` function returns a semi random number between `a` and `b`.
x = randrange(10, 100)

#### factorial(x)

The `factorial(x)` function calculates the product of all positive integers less than or equal to the given positive integer.
# x! = x*(x-1)*(x-2)....(1)
# returns 120
factorial(5)

#### combin(n, r)

The `combin(x,y)` function calculates the number of ways to choose a sample of r elements from a set of n distinct objects where order does not matter and replacements are not allowed.
# x!/(y!*(x-y)!)
# returns 10
combin(5,2)

### Trigonometric Functions

The following functions all use radians as the angle measurement. You can use `pi` to represent PI.

#### sin(angle)

The `sin(angle)` function is used to evaluate the trigonometric sine value for a given input angle. The input angle must be provided in radians.
# returns number 1
sin(pi/2)

#### cos(angle)

The `cos(angle)` function is used to evaluate the trigonometric cosine value for a given input angle. The input angle must be provided in radians.
# returns number 1
cos(0)

#### tan(angle)

The `tan(angle)` function is used to evaluate the trigonometric tangent value for a given input angle. The input angle must be provided in radians.
# returns number 1
tan(pi/4)

#### asin(value)

The `asin(value)` function is used to evaluate the trigonometric arcsine value (inverse sine) for a given input. The output angle is given in radians.
# returns number 1.57
asin(1)

#### acos(value)

The `acos(value)` function is used to evaluate the trigonometric arccosine value (inverse cosine) for a given input. The output angle is given in radians.
# returns number 0
acos(1)

#### atan2(x, y)

The `atan2(value)` function is used to evaluate the trigonometric arctangent value (inverse tangent) for a given x and y input. The output angle is given in radians.
# returns number -0.785
atan2(-1, 1)
# returns 2.36
atan2(1, -1)
The input is an angle measurement in degrees and the output is the angle measurement in radians.
# returns number .785
degrees(angle)
The input is an angle measurement in radians and the output is the angle measurement in degrees.
# returns number 180
degrees(pi)

## Vector and Vector Functions

The following functions provide operations for creating and using vectors in calculations.

#### vec(x, y), or vec(x,y,z)

Creates a Vector object representing a 3d vector with components identified as x, y, and z.
# Create a vector with components x=2, y=2, z=0
v1 = vec(2,2)
# Create a vector with components x=2, y=2, z=2
v2 = vec(2,2,2)
# Change a component of the vector:
v1.x = 3

Vectors can be added or subtracted from one another using standard +, - operators:
v1 = vec(2,2)
v2 = vec(1,1)
# Add the two vectors together:
v3 = v1 + v2 # Returns vec(3,3,0)

#### Multiplying and Dividing By A Scalar

Vectors can also by scaled using the standard *, / operators:
v1 = vec(2,2)
# Multiply by a scalar
v2 = 2 * v1 # Returns vec(4,4,0)
# Divide by a scalar
v3 = v1 / 2 # Returns vec(1,1,0)

#### dot(v1, v2)

Calculates the dot product of two Vector objects.
# Work is the dot product of Force (F) and displacement (r)
F = vec(2, 2)
r = vec(3, 3)
# returns 12
Work = dot(F, r)

#### cross(v1, v2)

Calculates the cross product for two vectors in three dimensional space.
# Torque is the cross product of Force and moment arm (r)
F = vec(2, 0, 0)
r = vec(0, 2, 0)
# returns Vector vec(0, 0, 4)
cross(F, r)

#### norm(vec)

Same as `hat`. See below.

#### hat(vec)

This function returns a unit vector representation of the given input vector. Its magnitude is 1 and the direction matches the direction of the input vector. This can be useful if you need just the direction of a vector, but not its magnitude.
• `vec` - any two or three dimensional vector.
Example:
u = hat(vec(3, 4)) # returns vec(0.6, 0.8, 0)
mag(u) # returns 1

#### mag(vec)

This function returns the scaler magnitude of any given vector. This is helpful when you want to know the length of a vector, for example, if you want the magnitude of a vector, but not the direction.
• `vec` - any two or three dimensional vector.
Example:
mag(vec(3, 4)) # returns 5
mag2(vec)
This function returns the scaler squared magnitude of any given vector.
• `vec` - any two or three dimensional vector.
Example:
mag2(vec(3, 4)) # returns 25

#### diff_angle(vec1, vec2)

This function returns the angle between two vectors. The angle is returned in radians.
• `vec1` - any two or three dimensional vector.
• `vec2` - any two or three dimensional vector.
Example:
diff_angle(vec(4, 4), vec(4, 0)) # returns 0.7853981633974484

#### diff_angle(vec1, vec2)

This function returns the angle between two vectors. The angle value is returned in radians.
• `vec1` - any two or three dimensional vector.
• `vec2` - any two or three dimensional vector.
Example:
diff_angle(vec(4, 4), vec(4, 0)) # returns 0.7853981633974484

#### proj(vec1, vec2)

This function returns the vector projection of `vec1` along `vec2`.
• `vec1` - any two or three dimensional vector.
• `vec2` - any two or three dimensional vector.

#### comp(vec1, vec2)

This function returns the scalar projection of `vec1` along `vec2`.
• `vec1` - any two or three dimensional vector.
• `vec2` - any two or three dimensional vector.

#### distance(point1, point2)

This function returns a scalar quantity representing the distance between two points.
• `point1` - any two or three dimensional vector representing a point in space.
• `point2` - any two or three dimensional vector representing a point in space.
Example:
distance(vec(5,5), vec(3,3)) # returns 2.8284271247461903

#### direction(vec)

This function returns a scalar angle measurement. This is helpful when you want to know the direction of a vector, like the direction of a velocity vector, or the direction of a force vector. The returned angle is given in radians, measured from the positive x axis.
• `vec` - any two or three dimensional vector.
Example:
direction(vec(4, 4)) # returns 0.7853981633974483

This function returns a two-dimensional vector representing the cartesian components of a polar coordinate corresponding to the magnitude of the radius and the radial angle.
• `radius` - scalar quantity representing the scalar distance of the radius of the
• `angle` - scalar quantity representing the angle measurement of the polar coordinate.
Example:
polar(10, pi/4) # returns vec(7.07, 7.07, 0)

#### get_rotated_position(position, angle, axis)

This function is simply used for finding a point that has been rotated a given angle about a specific axis. It is just a utility function that could be performed by doing some simple trigonometry calculations, but hey, why not make it easier for you?
• `position` - A vector representing the point that is rotated.
• `angle` - scalar quantity representing the angle measurement of rotation.
• `axis` - A 2D vector that identifies the axis point about which the position has been rotated.
Example:
get_rotated_position(vec(10, 0), pi, vec(0, 0)) # returns vec(-10, 0, 0)

## Other Useful Functions

Some other useful functions..._

#### rgb(r, g, b)

This function returns a hexadecimal value for the red, green, and blue input values. This can be useful for setting the color of an object based on the RGB color model.
• `r` - a value between 0 and 255 representing the RED of RGB.
• `g` - a value between 0 and 255 representing the GREEN of RGB.
• `b`- a value between 0 and 255 representing the BLUE of RGB.
Example:
color = rgb(100, 100, 0) # returns '#646400'

#### stop()

This function interrupts the simulation and stops it at the current frame.
`stop()` -> stops the simulation.
Example:
1
if buggy.pos.x > 100:
2
stop() # simulation stops

### Collision Functions

Currently `circle` ,`rectangle` , and `line` objects work with any of the collision functions. We are working to add other objects soon.
The following functions are meant to help users model collisions more easily. These functions could be used for other purposes rather than modeling collisions as Tychos is not a physics engine. These functions could be thought of as "overlap" functions. They return information about the overlap of objects.

#### has_collided(source, target)

This function returns a boolean true/false value when two objects are given as the source and target. It returns false if the two objects are not determined to be overlapping.
• `source` - `circle` or `rectangle` or `line ` object
• `target` - `circle` or `rectangle` or `line ` object
Example: 1
# Initial State
2
p1 = circle(pos=vec(15, 0), radius=10, color=rgb(0, 200, 200), opacity=.6)
3
b1 = rectangle(pos=vec(0, 0), size=vec(15, 15), color=rgb(200, 0, 200), opacity=.6)
4
5
p3 = circle(pos=vec(-15, 0), radius=10, color=rgb(0, 0, 200), opacity=.6)
1
# Calculations
2
has_collided(p1, b1) # returns True
3
has_collided(b1, p3) # returns True
4
has_collided(p1, p3) # returns False

#### get_mtv(source, target)

This function returns a two dimensional vector representing the minimum translation vector (MTV) that would be needed to separate two objects when they overlap. This can be used to simulate collision forces or to move objects apart based on the magnitude and direction of the MTV.
• `source` - `circle` or `rectangle` or `line ` object
• `target` - `circle` or `rectangle` or `line ` object
Example: 1
# Initial State
2
p1 = circle(pos=vec(0, 0), radius=10, color=rgb(200, 200, 200), opacity=.6)
3
p2 = circle(pos=vec(12, 10), radius=10, color=rgb(0, 200, 0), opacity=.6)
4
b1 = rectangle(pos=vec(-12, 0), size=vec(15, 15), color=rgb(200, 0, 0), opacity=.6)
5
mtv1 = arrow(pos=p1.pos, color="green")
6
mtv2 = arrow(pos=p1.pos, color="red")
1
# Calculations
2
mtv1.size = get_mtv(p1, p2)
3
mtv2.size = get_mtv(p1, b1)

#### get_intersections(source, target)

This function returns a list containing all the points where the object boundaries intersect. The points are vectors corresponding with the coordinates of those intersection locations. This can be used to identify exactly where the overlap is occurring in your scenarios.
• `source` - `circle` or `rectangle` or `line ` object
• `target` - `circle` or `rectangle` or `line ` object
The image below shows an example of the points of intersection between a rectangle and a line, but note, those points are being showed for demonstration only, and would not be visible unless you assign them to a visible object, in this case the position of two small circle objects. Example:
1
# Initial State
2
r = rectangle(pos=vec(-4, 0), size=vec(10,15), color="orange", opacity=.5)
3
r.rotate(.1)
4
l = line(pos=vec(0,10), pos2=vec(-10, -20))
1
# Calculations
2
points = get_intersections(r, ln)

### Logical Operators

The following operators are used to execute logical AND and OR comparisons for the use of evaluating logical statements.

#### and

This is used for performing a logical AND conjunction. For example, "A and B" is true only if A is true and B is true. "A and B" is false if either A or B is false.
1
A = True
2
B = True
3
A and B # returns true
4
B = False
5
A and B # returns false
You can use the `and` operator to test if two comparisons are both true:
1
x = 2
2
(x < 3) and (x == 2) # returns True
3
(x < 3) and (x != 2) # returns False

#### or

This is used for performing a logical OR conjunction. For example, "A or B" is true if A or B is true. "A or B" is false only if A and B are both false.
A = True
B = False
A or B # returns True
A = False
A or B # returns False
You can use the `or` operator to test if one of two comparisons are true:
x = 2
(x < 3) or (x == 3) # one is true, so returns True
(x < 1) or (x == 3) # both are false, so returns False

## Built-in Classes

Tychos has only a few classes that are used to create the basic simulated objects in the Tychos universe as well as a few tools for analyzing those objects in the simulated world. The graphical objects in Tychos that can be used are the `circle`, the `rectangle`, the `arrow`, the `line`, the `label`, the `spring` and the `poly_line`.

### circle

A `circle` is drawn as a colored circle in the World View. Below is the constructor for the `circle` class that shows its default values:
```circle( pos=vec(0,0), radius=10, color=default_color, border_size=0, border_color=default_color, border_style="none" image="", opacity=1, visible=True, motion_map=False, label_text="" label_color=default_color )```
• `pos` — The initial position of your `circle` as a vector with `x,y,z` coordinates.
• `radius` — The radius of the `circle`.
• `color` — The `circle` will be drawn in this color. Use HTML colors e.g. "#ff3300", "blue".
• `border_size` — The border thickness in pixels.
• `border_color` — The border will be drawn in this color. Use HTML colors e.g. "#ff3300", "blue".
• `border_style` — Sets the border as either solid (default = "none") or "dash" for a dashed border, or "dot" for a dotted border.
• `image` — A URL that identifies a JPEG, GIF, SVG or PNG image.
• `opacity` — The `circle` will be drawn with an opacity between 1 and 0, representing 100% opaque to 100% transparent.
• `visible` — The `circle` can be hidden from view by setting this flag to `False`.
• `motion_map` — This flag tells Tychos to attach a series of strobe images called a motion map.
• `label_text` - The text of an attached label.
• `label_color` - The color of the attached label text.
These attributes may also be modified on the `circle` after it is created. In particular, one will usually change the `pos` attribute of a `circle` in the Calculations editor to show movement. e.g.
# Initial State editor
c = circle()
c_big.color = "red"
c_green = circle(pos=vec(100, 0), color="green", opacity=.5)
# Calculations editor
c.pos = c.pos + vec(1, 0.25)

#### circle.remove()

`circle` objects, like all Tychos objects can be removed from the scenario world scope. Once this done, you will not be able to reference the object as it will be removed from your scenario's collection of viewable objects.

#### circle.rotate()

`circle` objects can be rotated.
`circle.rotate(angle=0, axis=vec(0, 0))` — Rotates the `circle` object by a given angle value in radian units. You can also provide an optional vector that identifies the axis of rotation. This method should only be called from the Calculations code editor.

#### circle.image

`circle` objects can also be represented with an image by setting the image attribute of the object. The text must be a URI link to a graphic file that can be a PNG, SVG, GIF, or JPEG image. A Circle that looks like a rocket.
The above image also demonstrates the use of the `direction` function as well as the `rotate` method:
`rocket.rotate(direction(rocket.v))`

### ellipse

A e`llipse` is drawn as a colored ellipse in the World View.
e1 = ellipse(pos=vec(0, 0), size=vec(10,5), color="green", opacity=.6)
e2 = ellipse(pos=vec(10, 0), size=vec(5,10), color="blue", opacity=.6)
e3 = ellipse(pos=vec(0, -10), size=vec(5,5), color="red", opacity=.6) Three ellipses with different sizes
Below is the constructor for the `ellipse` class that shows its default values:
```ellipse( pos=vec(0,0), size=vec(10,5), color=default_color, border_size=0, border_color=default_color, border_style="none" image="", opacity=1, visible=True, motion_map=False, label_text="" label_color=default_color )```
• `pos` — The initial position of your `ellipse` as a vector with `x,y,z` coordinates.
• `size` — The size of the `ellipse` given as a vector with `x,y,z` coordinates.
• `color` — The `ellipse` will be drawn in this color. Use HTML colors e.g. "#ff3300", "blue".
• `border_size` — The border thickness in pixels.
• `border_color` — The border will be drawn in this color. Use HTML colors e.g. "#ff3300", "blue".
• `border_style` — Sets the border as either solid (default = "none") or "dash" for a dashed border, or "dot" for a dotted border.
• `image` — A URL that identifies a JPEG, GIF, SVG or PNG image.
• `opacity` — The `ellipse` will be drawn with an opacity between 1 and 0, representing 100% opaque to 100% transparent.
• `visible` — The `ellipse` can be hidden from view by setting this flag to `False`.
• `motion_map` — This flag tells Tychos to attach a series of strobe images called a motion map.
• `label_text` - The text of an attached label.
• `label_color` - The color of the attached label text.
These attributes may also be modified on the `ellipse` after it is created, just like the `circle`.

#### ellipse.remove()

`ellipse` objects, like all Tychos objects can be removed from the scenario world scope. Once this done, you will not be able to reference the object as it will be removed from your scenario's collection of viewable objects.

#### ellipse.rotate()

`ellipse` objects can be rotated, just like the `circle.`
`ellipse.rotate(angle=0, axis=vec(0, 0))` — Rotates the `ellipse` object by a given angle value in radian units. You can also provide an optional vector that identifies the axis of rotation. This method should only be called from the Calculations code editor.

#### ellipse.image

`ellipse` objects can also be represented with an image by setting the image attribute of the object. The text must be a URI link to a graphic file that can be a PNG, SVG, GIF, or JPEG image. See the `circle` above for more detail

### rectangle

A `rectangle` is very similar to a `circle` but it is represented as a colored rectangle in the World View. Just as with the `circle`, Tychos only uses the width and height attributes for display. You can define how these attributes change given the rules of the simulation that you define. Below is the constructor for the `rectangle` class that shows its default values:
```rectangle( pos=vec(0,0), size=vec(10,5), color=default_color, border_size=0, border_color=default_color, border_style="none" image="", opacity=1, visible=True, motion_map=False, label_text="" label_color=default_color )```
• `pos` — The initial position of your `rectangle` as a vector with `x,y,z` coordinates.
• `size` — The size of the `rectangle` given as a vector with `x,y,z` coordinates.
• `color` — The `rectangle` will be drawn in this color. Use HTML colors e.g. "#ff3300", "blue".
• `border_size` — The border thickness in pixels.
• `border_color` — The border will be drawn in this color. Use HTML colors e.g. "#ff3300", "blue".
• `border_style` — Sets the border as either solid (default = "none") or "dash" for a dashed border, or "dot" for a dotted border.
• `image` — A URL that identifies a JPEG, GIF, SVG or PNG image.
• `opacity` — The `rectangle` will be drawn with an opacity between 1 and 0, representing 100% opaque to 100% transparent.
• `visible` — The `rectangle` can be hidden from view by setting this flag to `False`.
• `motion_map` — This flag tells Tychos to attach a series of strobe images called a motion map.
• `label_text` - The text of an attached label.
• `label_color` - The color of the attached label text.
These attributes may also be modified on the `rectangle` object after it is created. In particular, one will usually change the `pos` attribute in the Calculations editor to show movement. e.g.
# Initial State editor
r1 = rectangle(pos=vec(0, 0), size=vec(10, 10), color="green")
r2 = rectangle(pos=vec(20, 0), size=vec(10, 20), color="blue")
r3 = rectangle(pos=vec(40, 0), size=vec(20, 10), color="orange")
# Calculations editor
r1.pos = r1.pos + vec(1, 0.25)

#### rectangle.remove()

`rectangle` objects, like all Tychos objects can be removed from the scenario world scope. Once this done, you will not be able to reference the object as it will be removed from your scenario's collection of viewable objects.

#### rectangle.rotate

You can also rotate a `rectangle` object in order to simulate rotational behavior.
`rectangle.rotate(angle=0, axis=vec(0, 0))` — Rotates the `rectangle` object by a given angle value in radian units. You can also provide an optional matrix that identifies the center of rotation. This method should only be called from the Calculations code editor. Three different Rectangle objects rotated at different angles
Example:
# Calculations editor
r1.rotate(-pi/4)
rectangle.image
Just as with `circle` objects, `rectangle` objects can also be represented with an image by setting the image attribute of the object.
r.image = "https://some.image.url.jpg"

### arrow

The `arrow` class represents a graphical arrow and is commonly used to illustrate vectors, but can be used for representing anything in your simulations.
Below is the constructor for the `arrow` class that shows its default values:
```arrow( pos=vec(0,0), size=vec(0,1), color=default_color, stroke=0, style="none" opacity=1, show_components=False, visible=True, motion_map=False, )```
• `pos` — The initial position of your `arrow` tail as a vector with `x,y,z` coordinates.
• `size` — The size of the `arrow` given as a vector with `x,y,z` coordinates.
• `color` — The `arrow` will be drawn in this color. Use HTML colors e.g. "#ff3300", "blue".
• `stroke` — The `arrow` thickness in pixels.
• `style` — An `arrow` can have a "dash" style, or a "dot" style, or "none" which is the default.
• `opacity` — The `arrow` will be drawn with an opacity between 1 and 0, representing 100% opaque to 100% transparent.
• `show_components` — This flag tells Tychos to attach additional x and y component arrows.
• `visible` — The `arrow` can be hidden from view by setting this flag to `False`.
• `motion_map` — This flag tells Tychos to attach a series of strobe images called a motion map. Arrow without components Arrow with components
Example — The illustrations above were drawn using these commands:
# Initial State editor
c = circle(pos=vec(0,0), color="green")
a = arrow(pos=c.pos, size=vec(20, 20), color="purple")
a.show_components = True

#### arrow.remove()

`arrow` objects, like all Tychos objects can be removed from the scenario world scope. Once this done, you will not be able to reference the object as it will be removed from your scenario's collection of viewable objects.

### line

The `line` class draws a line and is commonly used to illustrate some connecting member like a string or cable, but could really represent anything you like.
Below is the constructor for the `line` class that shows its default values:
```line( pos=vec(0,0), pos2=vec(1,0), color=default_color, stroke=1, style="none", opacity=1, visible=True, motion_map=False )```
• `pos` — coordinates for the starting point of the `line` as vector
• `pos2` — coordinates of the termination point of the `line` as a vector.
• `color` — HTML color value for your `line`, e.g. "red" or "#ff0000".
• `stroke` — Stroke value that determines the visual thickness of the `line`. This is measured in pixels.
• `style` — Sets the `line` as either solid (default = "none") or "dash" for a dashed line, or "dot" for a dotted line.
• `opacity` — The `line` will be drawn with an opacity between 1 and 0, representing 100% opaque to 100% transparent.
• `visible` — The `line` can be hidden from view by setting this flag to `False`.
• `motion_map` — This flag tells Tychos to attach a series of strobe images called a motion map. Example:
myLine = line(pos=vec(0, 0), pos2=vec(20, 20), color="purple", stroke=2)
anotherLine = line(pos=vec(0, 0), pos2=vec(10, 20), color="green", stroke=10)

#### line.remove()

`line` objects, like all Tychos objects can be removed from the scenario world scope. Once this done, you will not be able to reference the object as it will be removed from your scenario's collection of viewable objects.

### poly_line

The `poly_line` class draws a series of connected lines between a given set of points. This object can be used to represent a complex path or a shape other than a circle or rectangle.
Below is the constructor for the `poly_line` class that shows its default values:
```poly_line( pos=vec(0,0), color=default_color, stroke=1, style="none" fill=False opacity=1, visible=True, motion_map=False } )```
• `pos` — coordinates for the starting point of the `poly_line` as a vector.
• `color` — HTML color value for your `poly_line`, e.g. "red" or "#ff0000".
• `stroke` — Stroke value that determines the visual thickness of the `poly_line`. This is measured in pixels.
• `style` — Can be `"none"` for solid segments, `"dash"` for dashed line segments or `"dot"` for dotted line segments.
• `fill` — Boolean value (True or False) for displaying the `poly_line` object as a filled in solid.
• `opacity` — The `poly_line` will be drawn with an opacity between 1 and 0, representing 100% opaque to 100% transparent.
• `visible` — The `poly_line` can be hidden from view by setting this flag to `false`.
• `motion_map` — This flag tells Tychos to attach a series of strobe images called a motion map.
`poly_line` objects have a number of methods for manipulating the `poly_line` points, like adding new points, changing existing points, removing points, etc:
• `set_points: (points)` -> Set the points for the `poly_line` given a `List` of points.
• `translate: (delta_position)` -> Move all the points according to a vector.
• `rotate: (angle, axis)` -> Transform the points a certain angle measurement about an axis. This axis is relative to the first point in the `poly_line`.
• `npoints():` -> Returns the number of points in the `poly_line`.
• `append: (*points)` -> Add a point (or many points) to the end of the `poly_line`.
• `unshift: (*points)` -> Add a point (or many points) at the beginning of the `poly_line`.
• `shift: ()` -> Remove the first point in the `poly_line` object.
• `splice: (start, how_many, *points)` -> Insert a point or several points anywhere at the specific index position. You can also identify how many points you would like to remove from the `poly_line` as well.
• `pop: (n)` -> Get the vector for point number n and remove it. Can use negative values, where -1 is the last point, -2 the next to the last, etc.
• `clear: ()` -> Remove all the points in the `poly_line`.
• `modify: (n, point)` -> Modify the point at the specified n position, replacing it with the given vector.
• `slice: (start, end)` -> Returns the set of points (but does not remove them) from the `poly_line` object beginning at the `start` value and ending at the `end` index position. Three poly_line objects showing different styles and fills.

#### poly_line.remove()

`poly_line` objects, like all Tychos objects can be removed from the scenario world scope. Once this done, you will not be able to reference the object as it will be removed from your scenario's collection of viewable objects.

### spring

A `spring` is a visual representation of a common elastic connector that displays a given number of coils that dynamically change shape once the dimensions of the `spring` are changed in the Calculations Pane.
Below is the constructor for the `spring` class that shows its default values:
```spring( pos=vec(0,0), pos2=vec(1,0), color=default_color, coils=5, width=10, stroke=1, opacity=1, visible=True, motion_map=False )```
• `pos` — coordinates for the starting point of the `spring` as a 2D vector.
• `pos2` — coordinates of the termination point of the `spring` as 2D vector
• `color` — HTML color value for your `spring`, e.g. "red" or "#ff0000".
• `coils` — The number "coil" zig-zags.
• `width` — The width of the "coil" zig-zags.
• `stroke` — Stroke value that determines the visual thickness of the `spring`. This is measured in pixels.
• `opacity` — The `spring` will be drawn with an opacity between 1 and 0, representing 100% opaque to 100% transparent.
• `visible` — The `spring` can be hidden from view by setting this flag to `false`.
• `motion_map` — This flag tells Tychos to attach a series of strobe images called a motion map. Three different Spring objects
The code below shows the three different `spring` objects above that have different lengths, widths and coil numbers. The `circle` objects are shown just for reference.
# Initial State editor
c1 = circle(pos=vec(0, 0), radius=2, color="green")
spring1 = spring(pos=vec(0, 20), pos2=c1.pos, color="black", coils=20, width=2)
c2 = circle(pos=vec(10, 0), radius=2, color="green")
spring2 = spring(pos=vec(10, 20), pos2=c2.pos, color="black", coils=10, width=4)
c3 = circle(pos=vec(20, 0), radius=2, color="green")
spring3 = spring(pos=vec(20, 20), pos2=c3.pos, color="black", coils=20, width=2)
These attributes may also be modified after the `spring` is created.

#### spring.remove()

`spring` objects, like all Tychos objects can be removed from the scenario world scope. Once this done, you will not be able to reference the object as it will be removed from your scenario's collection of viewable objects.

### label

You can add text labels to any scenario using the `label` class.
Below is the constructor for the `label` class that shows its default values:
```label( pos=vec(0,0), size=vec(10,10), text="", color=default_color, opacity=1, visible=True, motion_map=False )```
• `pos` — coordinates for the center point of the `label` as a 2D vector.
• `size` — The width and height of the `label` as a 2D vector.
• `text` — The text of the `label` as a string.
• `color` — HTML color value for your `label`, e.g. "red" or "#ff0000".
• `opacity` — The `label` will be drawn with an opacity between 1 and 0, representing 100% opaque to 100% transparent.
• `visible` — The `label` can be hidden from view by setting this flag to `False`.
• `motion_map` — This flag tells Tychos to attach a series of strobe images called a motion map.
These attributes may also be modified after the `label` object is created. Here is an example of how to make several `label` objects: # Initial State editor
label1 = label(pos=vec(0, 100), size=vec(50, 50), text="Cat", color="green")
label2 = label(pos=vec(0, 0), size=vec(150, 150), text="Dog", color="red")
label3 = label(pos=vec(0, -100), size=vec(50, 50), text="Mouse", color="blue")

#### label.remove()

`label` objects, like all Tychos objects can be removed from the scenario world scope. Once this done, you will not be able to reference the object as it will be removed from your scenario's collection of viewable objects.

#### label.rotate

You can rotate a label as shown above:
label3.rotate(pi/4)

## Interface Widgets

Tychos also provides several "widgets" for displaying data in different ways as well as adding user interactivity so that your simulations can respond to input.