Class Rubygame::Ftor
In: lib/rubygame/ftor.rb
Parent: Object

NOTE: Ftor is DEPRECATED and will be removed in Rubygame 3.0! A mostly-compatible vector class will be provided at or before that time.

NOTE: you must require ‘rubygame/ftor’ manually to gain access to Rubygame::Ftor. It is not imported with Rubygame by default!

Ftor (“Fake vecTOR”), a vector-like class for 2D position/movement.

(NB: See angle for an important note about why angles appear to be the opposite of what you may expect.)

Ftor is useful for storing 2D coordinates (x,y) as well as vector quantities such as velocity and acceleration (representationally, points and vectors are equivalent.) Although Ftors are always represented internally as Cartesian coordinates (x, y), it is possible to deal with an Ftor as polar coordinates (angle, magnitude) instead. See new_am and set_am!, for example.

Ftor is a “fake” vector because it has certain convenient properties which differ from “true” vectors (i.e. vectors in a strict mathematical sense).

Unlike vectors, Ftors may be multiplied or divided to another Ftor. This is equivalent to multiplying or dividing each component by the corresponding component in the second Ftor. If you like, you can think of this feature as scaling each component of the Ftor by a separate factor:

  Ftor(a,b) * Ftor(c,d)  =  Ftor(a*c, b*d)

Of course, Ftors also have the usual vector behavior for addition/subraction between two Ftors, and multiplication/division of an Ftor by a scalar:

  Ftor(a,b) + Ftor(c,d) = Ftor(a+c, b+d)
  Ftor(a,b) * n = Ftor(a*n, b*n)

Additionally, Ftor contains functions for manipulating itself. You can both get and set such properties as angle, magnitude, unit, and normal, and the Ftor will change in-place as needed. For example, if you set angle=, the vector will change to have the new angle, but keeps the same magnitude as before.

Ftor attempts to save processing time (at the expense of memory) by storing secondary properties (angle, magnitude, etc.) whenever they are calculated,so that they need not be calculated repeatedly. If the vector changes, the properties will be calculated again the next time they are needed. (In future versions, it may be possible to disable this feature for certain Ftors, for example if they will change very often, to save memory.)

Methods

*   +   -   -@   /   ==   []   _clear   a   a=   align!   angle   angle=   angle_with   dot   inspect   inspect_am   m   m=   magnitude   magnitude=   n   n=   new   new_am   new_from_to   normal   normal=   pretty   pretty_am   reverse!   rotate   rotate!   set!   set_am!   to_a   to_ary   to_s   to_s_am   u   u=   udot   unit   unit=   x=   y=  

Constants

PI = Math::PI
HALF_PI = PI*0.5
THREE_HALF_PI = PI*1.5
TWO_PI = PI*2

Attributes

x  [R] 
y  [R] 

Public Class methods

Create a new Ftor by specifying its x and y components. See also new_am and new_from_to.

[Source]

# File lib/rubygame/ftor.rb, line 82
        def initialize(x,y)
    Rubygame.deprecated("Rubygame::Ftor", "3.0")
    @x, @y = x, y
        end

Create a new Ftor by specifying its angle (in radians) and magnitude. See also new.

[Source]

# File lib/rubygame/ftor.rb, line 89
        def self.new_am(a,m)
                v = self.new(1,0)
    v.a, v.m = a, m
                return v
        end

Returns a new Ftor which represents the difference in position of two points p1 and p2. (p1 and p2 can be Ftors, size-2 Arrays, or anything else which has two numerical components and responds to #[].)

In other words, assuming v is the Ftor returned by this function:

  p1 + v = p2

[Source]

# File lib/rubygame/ftor.rb, line 101
  def self.new_from_to(p1,p2)
    return self.new(p2[0]-p1[0],p2[1]-p1[1])
  end

Public Instance methods

Perform multiplication of this Ftor by the scalar other, like so:

  Ftor(a,b) * n = Ftor(a*n, b*n)

However, if this causes TypeError, attempt to extract indices 0 and 1 with other’s #[] operator, and multiply them into the corresponding components of this Ftor, like so:

  Ftor(a,b) * Ftor(c,d) = Ftor(a*c, b*d)
  Ftor(a,b) * [c,d]     = Ftor(a*c, b*d)

[Source]

# File lib/rubygame/ftor.rb, line 215
        def *(other)
    return self.class.new(@x*other,@y*other)
  rescue TypeError
    return self.class.new(@x*other[0],@y*other[1])
        end

Perform vector addition with this Ftor and other, adding them on a component-by-component basis, like so:

  Ftor(a,b) + Ftor(c,d)  =  Ftor(a+c, b+d)

[Source]

# File lib/rubygame/ftor.rb, line 198
        def +(other)
    return self.class.new(@x+other[0],@y+other[1])
        end

Like #+, but performs subtraction instead of addition.

[Source]

# File lib/rubygame/ftor.rb, line 203
        def -(other)
    return self.class.new(@x-other[0],@y-other[1])
        end

The reverse of this Ftor. I.e., all components are negated. See also reverse!.

[Source]

# File lib/rubygame/ftor.rb, line 186
  def -@
    self.class.new(-@x,-@y)
  end

Like #*, but performs division instead of multiplication.

[Source]

# File lib/rubygame/ftor.rb, line 222
        def /(other)
                x, y = @x.to_f, @y.to_f
    return self.class.new(x/other,y/other)
  rescue TypeError
    return self.class.new(x/other[0],y/other[1])
        end

True if this Ftor is equal to other, when both have been converted to Arrays via to_a. In other words, a component-by-component equality check.

[Source]

# File lib/rubygame/ftor.rb, line 180
        def ==(other)
                to_a() == other.to_a
        end

Return the +i+th component of this Ftor, as if it were the Array returned by to_a.

[Source]

# File lib/rubygame/ftor.rb, line 174
        def [](i)
                [@x,@y][i]
        end

Clears stored values for angle, magnitude, normal, and unit, so that they will be recalculated the next time they are needed. Intended for internal use, but might be useful in other situations.

[Source]

# File lib/rubygame/ftor.rb, line 369
        def _clear
                @angle = nil
                @magnitude = nil
                @normal = nil
                @unit = nil
                return self
        end
a()

Alias for angle

a=(a)

Alias for angle=

align!(other)

Alias for unit=

Return the angle (radians) this Ftor forms with the positive X axis. This is the same as the Ftor’s angle in a polar coordinate system.

IMPORTANT: Because the positive Y axis on the Rubygame::Screen points downwards, an angle in the range 0..PI will appear to point downwards, rather than upwards! This also means that positive rotation will appear clockwise, and negative rotation will appear counterclockwise! This is the opposite of what you would expect in geometry class!

[Source]

# File lib/rubygame/ftor.rb, line 238
        def angle
                @angle or @angle = Math.atan2(@y,@x)
        end

Set the angle (radians) of this Ftor from the positive X axis. Magnitude is preserved.

[Source]

# File lib/rubygame/ftor.rb, line 244
        def angle=(a)
                m = magnitude()
                set!( Math.cos(a)*m, Math.sin(a)*m )
        end

Return the difference in angles (radians) between this Ftor and other.

[Source]

# File lib/rubygame/ftor.rb, line 322
        def angle_with(other)
                Math.acos( self.udot(other) )
        end

Return the dot product (aka inner product) of this Ftor and other. The dot product of two vectors v1 and v2 is:

  v1.x * v2.x + v1.y * v2.y

[Source]

# File lib/rubygame/ftor.rb, line 312
        def dot(other)
                @x*other[0] + @y*other[1]
        end

Same as to_s, but this Ftor’s object_id is also displayed.

[Source]

# File lib/rubygame/ftor.rb, line 131
        def inspect
                "#<#{self.class}:#{object_id}: %f, %f>"%[@x,@y]
        end

Same as to_s_am, but this Ftor’s object_id is also displayed.

[Source]

# File lib/rubygame/ftor.rb, line 148
        def inspect_am
                "#<#{self.class}:AM:#{object_id}: %f, %f>"%[angle(),magnitude()]
        end
m()

Alias for magnitude

m=(m)

Alias for magnitude=

Returns the magnitude of the Ftor, i.e. its length from tail to head. This is the same as the Ftor’s magnitude in a polar coordinate system.

[Source]

# File lib/rubygame/ftor.rb, line 254
        def magnitude
                @magnitude or @magnitude = Math.hypot(@x,@y)
        end

Modifies the magnitude of the Ftor, preserving its angle.

In other words, the Ftor will point in the same direction, but it will be a different length from tail to head.

[Source]

# File lib/rubygame/ftor.rb, line 262
        def magnitude=(m)
                new = unit() * m
                set!(new.x, new.y)
        end
n()

Alias for normal

n=(other)

Alias for normal=

Return a new unit Ftor which is perpendicular to this Ftor (rotated by pi/2 radians, to be specific).

[Source]

# File lib/rubygame/ftor.rb, line 272
        def normal
                @normal or @normal = unit().rotate(HALF_PI)
        end

Rotate this Ftor in-place, so that it is perpendicular to other. This Ftor will be at an angle of -pi/2 to other.

[Source]

# File lib/rubygame/ftor.rb, line 278
        def normal=(other)
    set!( *(self.class.new(*other).unit().rotate(-HALF_PI) * magnitude()) )
        end

“Pretty print”. Same as to_s, but components are displayed as rounded floats to 3 decimal places, for easy viewing.

[Source]

# File lib/rubygame/ftor.rb, line 143
        def pretty
                "#<#{self.class}: [%0.3f, %0.3f]>"%[@x,@y]
        end

“Pretty print” with angle and magnitude. Same as to_s_am, but components are displayed as rounded floats to 3 decimal places, for easy viewing.

[Source]

# File lib/rubygame/ftor.rb, line 162
        def pretty_am
                "#<#{self.class}:AM: [%0.3f, %0.3f]>"%[angle(),magnitude()]
        end

Like #-@, but reverses this Ftor in-place.

[Source]

# File lib/rubygame/ftor.rb, line 191
  def reverse!
    set!(-@x,-@y)
  end

Like rotate!, but returns a duplicate instead of rotating this Ftor in-place.

[Source]

# File lib/rubygame/ftor.rb, line 362
        def rotate(radians)
                self.dup.rotate!(radians)
        end

Rotate this Ftor in-place by angle (radians). This is the same as adding angle to this Ftor’s angle.

IMPORTANT: Positive rotation will appear clockwise, and negative rotation will appear counterclockwise! See angle for the reason.

[Source]

# File lib/rubygame/ftor.rb, line 344
        def rotate!(angle)
#               case(angle)
#               when HALF_PI, -THREE_HALF_PI
#                       self.set!(@y,-@x)
#               when THREE_HALF_PI, -HALF_PI
#                       self.set!(-@y,@x)
#               when PI, -PI
#                       self.set!(@y,-@x)
#               when 0, TWO_PI, -TWO_PI
#                       self.set!(@y,-@x)
#               else
                        self.a += angle
#               end
                return self
        end

Modify the x and y components of the Ftor in-place

[Source]

# File lib/rubygame/ftor.rb, line 120
        def set!(x,y)
    @x, @y = x,y
                _clear()
        end

Modify the angle (in radians) and magnitude of the Ftor in-place

[Source]

# File lib/rubygame/ftor.rb, line 126
        def set_am!(a,m)
    self.angle, self.magnitude = a, m
  end

Returns an Array of this Ftor’s components, [x,y].

[Source]

# File lib/rubygame/ftor.rb, line 167
        def to_a
                [@x,@y]
        end
to_ary()

Alias for to_a

Display this Ftor in the format: “#”. x and y are displayed as floats at full precision. See also pp.

[Source]

# File lib/rubygame/ftor.rb, line 137
        def to_s
                "#<#{self.class}: [%f, %f]>"%[@x,@y]
        end

Display this Ftor in the format: “#”. angle and magnitude are displayed as floats at full precision. See also to_s and pp_am.

[Source]

# File lib/rubygame/ftor.rb, line 155
  def to_s_am
                "#<#{self.class}:AM: [%f, %f]>"%[angle(),magnitude()]
  end
u()

Alias for unit

u=(other)

Alias for unit=

Return the dot product of unit vectors of this Ftor and other.

[Source]

# File lib/rubygame/ftor.rb, line 317
        def udot(other)
                unit().dot(self.class.new(*other).unit)
        end

Return the unit vector of the Ftor, i.e. an Ftor with the same direction, but a magnitude of 1. (This is sometimes called a “normalized” vector, not to be confused with a vector’s normal.)

[Source]

# File lib/rubygame/ftor.rb, line 288
        def unit
                m = magnitude().to_f
                @unit or @unit = Ftor.new(@x/m, @y/m)
        end

Rotates this Ftor in-place, so that its unit vector matches the unit vector of the given Ftor.

In other words, changes the angle of this Ftor to be the same as the angle of the given Ftor, but this Ftor’s magnitude does not change.

[Source]

# File lib/rubygame/ftor.rb, line 301
        def unit=(other)
                set!( *(self.class.new(*other).unit() * magnitude()) )
        end

Set the x component of the Ftor.

[Source]

# File lib/rubygame/ftor.rb, line 107
        def x=(value)
    @x = value
    _clear()
        end

Set the y component of the Ftor.

[Source]

# File lib/rubygame/ftor.rb, line 114
        def y=(value)
    @y = value
    _clear()
        end

[Validate]