QUARTER_PI

A number constant that's approximately 0.7854.

QUARTER_PI is one-fourth the value of the mathematical constant π. It's useful for many tasks that involve rotation and oscillation. For example, calling rotate(QUARTER_PI) rotates the coordinate system QUARTER_PI radians, which is an eighth turn (45˚).

Note: TWO_PI radians equals 360 degrees, PI radians equals 180 degrees, HALF_PI radians equals 90 degrees, and QUARTER_PI radians equals 45 degrees.

Examples

QUARTER_PI example 1

function setup()
  size(100, 100)

  background(200)

  -- Draw an arc from 0 to QUARTER_PI.
  arc(50, 50, 80, 80, 0, QUARTER_PI)

  describe('A one-eighth slice of a circle drawn in white on a gray background.')
end

QUARTER_PI example 2

function setup()
  size(100, 100)

  background(200)

  -- Translate the origin to the center.
  translate(50, 50)

  -- Draw a line.
  line(0, 0, 40, 0)

  -- Rotate an eighth turn.
  rotate(QUARTER_PI)

  -- Draw the same line, rotated.
  line(0, 0, 40, 0)

  describe('Two black lines that form a "V" opening towards the bottom-right corner of a gray square.')
end

QUARTER_PI example 3

function setup()
  size(100, 100)

  describe(
    'A red circle and a blue circle oscillate from left to right on a gray background. The red circle appears to chase the blue circle.'
  )
end

function draw()
  background(200)

  -- Translate the origin to the center.
  translate(50, 50)

  -- Calculate the x-coordinates.
  local x1 = 40 * sin(frameCount * 0.05)
  local x2 = 40 * sin(frameCount * 0.05 + QUARTER_PI)

  -- Style the oscillators.
  noStroke()

  -- Draw the red oscillator.
  fill(255, 0, 0)
  circle(x1, 0, 20)

  -- Draw the blue oscillator.
  fill(0, 0, 255)
  circle(x2, 0, 20)
end

This reference page contains content adapted from p5.js and Processing by p5.js Contributors and Processing Foundation, licensed under CC BY-NC-SA 4.0.

QUARTER_PI

Examples

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