Class: Amaterasu::GameBoy::Ppu::Modes::Rendering::SpriteFetcher

Inherits:
Object
  • Object
show all
Defined in:
lib/amaterasu/game_boy/ppu/modes/rendering/sprite_fetcher.rb

Overview

Responsible for fetching Sprites tiles, decoding Sprite pixels and outputting them into the Sprite FIFO.

Defined Under Namespace

Classes: SpritePixel

Constant Summary collapse

BIT_MASK_BG_WIN_PRIORITY_SET = 
1 << 3
BIT_MASK_USE_OBP1_PALETTE = 
1 << 2

Instance Method Summary collapse

Constructor Details

#initialize(ppu, sprite_fifo) ⇒ SpriteFetcher

Returns a new instance of SpriteFetcher.



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# File 'lib/amaterasu/game_boy/ppu/modes/rendering/sprite_fetcher.rb', line 16

def initialize(ppu, sprite_fifo)
  @ppu = ppu
  @sprite_fifo = sprite_fifo

  @step = :fetch_tile_index
  @completed = false
  @fetch_duration = 6

  @current_sprite = nil

  @tile_index     = nil
  @tile_data_low  = nil
  @tile_data_high = nil
  @tile_pixels    = nil
  @encoded_pixels = Array.new(8)
end

Instance Method Details

#done? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/amaterasu/game_boy/ppu/modes/rendering/sprite_fetcher.rb', line 50

def done?
  @completed
end

#start_for(sprite) ⇒ Object 



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# File 'lib/amaterasu/game_boy/ppu/modes/rendering/sprite_fetcher.rb', line 33

def start_for(sprite)
  @current_sprite = sprite
  @step = :fetch_tile_index
  @completed = false
  @fetch_duration = 6
end

#tick ⇒ Object

Core fetch state machine (Takes 2 dots per step).



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# File 'lib/amaterasu/game_boy/ppu/modes/rendering/sprite_fetcher.rb', line 42

def tick
  case @step
  when :fetch_tile_index     then fetch_tile_index
  when :fetch_tile_data_low  then fetch_tile_data_low
  when :fetch_tile_data_high then fetch_tile_data_high
  end
end