Class: Doom::Render::ScreenMelt

Inherits:
Object
  • Object
show all
Defined in:
lib/doom/render/screen_melt.rb

Overview

DOOM’s screen melt/wipe effect from wipe.c. Each column slides down at a slightly different speed, revealing the new screen underneath.

Constant Summary collapse

WIDTH = 
SCREEN_WIDTH
HEIGHT = 
SCREEN_HEIGHT
MELT_SPEED =

~8 pixels per frame (Chocolate Doom does HEIGHT/15 at 35fps)

HEIGHT / 30

Instance Method Summary collapse

Constructor Details

#initialize(old_screen, new_screen) ⇒ ScreenMelt

Returns a new instance of ScreenMelt.



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# File 'lib/doom/render/screen_melt.rb', line 13

def initialize(old_screen, new_screen)
  # Snapshot both screens (arrays of palette indices, 320x240)
  @old = old_screen.dup
  @new = new_screen.dup
  @done = false

  # Initialize column offsets (from wipe_initMelt in wipe.c)
  # Column 0 gets random negative offset, each subsequent column
  # varies by -1/0/+1 from previous, creating a jagged melt line
  @y = Array.new(WIDTH)
  @y[0] = -(rand(16))
  (1...WIDTH).each do |i|
    @y[i] = @y[i - 1] + (rand(3) - 1)
    @y[i] = -15 if @y[i] < -15
    @y[i] = 0 if @y[i] > 0
  end
end

Instance Method Details

#done? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/doom/render/screen_melt.rb', line 31

def done?
  @done
end

#update(framebuffer) ⇒ Object

Advance one tic. Returns the composited framebuffer.



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# File 'lib/doom/render/screen_melt.rb', line 36

def update(framebuffer)
  all_done = true

  WIDTH.times do |x|
    if @y[x] < 0
      @y[x] += 1
      all_done = false
      # Column hasn't started melting yet - show old screen
      HEIGHT.times { |row| framebuffer[row * WIDTH + x] = @old[row * WIDTH + x] }
    elsif @y[x] < HEIGHT
      all_done = false
      dy = @y[x]

      # Top part: new screen revealed
      dy.times do |row|
        framebuffer[row * WIDTH + x] = @new[row * WIDTH + x]
      end

      # Bottom part: old screen shifted down
      (dy...HEIGHT).each do |row|
        src_row = row - dy
        framebuffer[row * WIDTH + x] = @old[src_row * WIDTH + x]
      end

      @y[x] += MELT_SPEED
    else
      # Column fully melted - show new screen
      HEIGHT.times { |row| framebuffer[row * WIDTH + x] = @new[row * WIDTH + x] }
    end
  end

  @done = all_done
end