🌈 Creating an Animated Plasma Effect in Ruby2D

1Setting Up the Window

First, we need to require Ruby2D and configure our window:

require 'ruby2d'

set title: "Plasma Effect"
set width: 640
set height: 480
set background: 'black'

This creates a 640x480 window with a black background.

2Creating the Grid

Instead of calculating colors for every pixel (which would be slow), we create a grid of rectangles:

GRID_WIDTH = 80
GRID_HEIGHT = 60
CELL_WIDTH = Window.width / GRID_WIDTH
CELL_HEIGHT = Window.height / GRID_HEIGHT

This divides our window into an 80x60 grid. Each cell will be 8x8 pixels.

3Building the Rectangle Grid

Now we create a rectangle for each grid cell:

plasma_grid = []
GRID_HEIGHT.times do |y|
  row = []
  GRID_WIDTH.times do |x|
    rect = Rectangle.new(
      x: x * CELL_WIDTH,
      y: y * CELL_HEIGHT,
      width: CELL_WIDTH,
      height: CELL_HEIGHT,
      color: 'black'
    )
    row << rect
  end
  plasma_grid << row
end

This creates a 2D array where plasma_grid[y][x] gives us the rectangle at position (x, y).

4The Heart of Plasma: The Math

This is where the magic happens! The plasma function combines multiple sine waves:

def plasma_color(x, y, time)
  # Four different sine waves
  v1 = Math.sin(x * 0.1 + time)
  v2 = Math.sin(y * 0.1 + time * 0.8)
  v3 = Math.sin((x + y) * 0.08 + time * 0.5)
  v4 = Math.sin(Math.sqrt(x * x + y * y) * 0.05 + time)
  
  # Average them together
  value = (v1 + v2 + v3 + v4) / 4.0
  
  # ... (color conversion continues)
end

Understanding Each Wave:

• v1: Horizontal wave moving right
• v2: Vertical wave moving down (slightly faster)
• v3: Diagonal wave from top-left to bottom-right
• v4: Circular/radial wave from center

By adding time to each wave with different speeds, they animate at different rates, creating complex patterns.

5Converting Math to Colors

The sine waves give us values between -1 and 1. We need to convert these to colors:

# Normalize to 0-1 range
hue = (value + 1.0) * 0.5

# Create RGB colors using sine waves offset by 120 degrees
r = (Math.sin(hue * Math::PI * 2) * 0.5 + 0.5)
g = (Math.sin((hue + 0.33) * Math::PI * 2) * 0.5 + 0.5)
b = (Math.sin((hue + 0.66) * Math::PI * 2) * 0.5 + 0.5)

[r, g, b, 1.0]  # Return RGBA array

This creates a rainbow gradient by offsetting the red, green, and blue channels.

6Animation Loop

Finally, we animate by updating colors every frame:

time = 0.0

update do
  time += 0.03  # Increment time each frame
  
  GRID_HEIGHT.times do |y|
    GRID_WIDTH.times do |x|
      color = plasma_color(x, y, time)
      plasma_grid[y][x].color = color
    end
  end
end

show  # Start the window

The update block runs every frame (typically 60 times per second), recalculating colors based on the current time.