Class: PSX::GPU

Inherits:
Object
  • Object
show all
Defined in:
lib/psx/gpu.rb

Overview

Graphics Processing Unit Handles 2D/3D rendering to VRAM

Constant Summary collapse

VRAM_WIDTH =

VRAM dimensions

1024
VRAM_HEIGHT = 
512
STAT_TEXTURE_PAGE_X =

Status register bits

0x0000_000F
STAT_TEXTURE_PAGE_Y =

Texture page X base (N*64)

0x0000_0010
STAT_SEMI_TRANSPARENCY =

Texture page Y base (N*256)

0x0000_0060
STAT_TEXTURE_DEPTH =

Semi-transparency mode

0x0000_0180
STAT_DITHER =

Texture color depth

0x0000_0200
STAT_DRAW_TO_DISPLAY =

Dither enabled

0x0000_0400
STAT_SET_MASK_BIT =

Drawing to display area allowed

0x0000_0800
STAT_DRAW_PIXELS =

Set mask bit when drawing

0x0000_1000
STAT_INTERLACE_FIELD =

Draw pixels (0=always, 1=not to masked)

0x0000_2000
STAT_REVERSE_FLAG =

Interlace field

0x0000_4000
STAT_TEXTURE_DISABLE =

Reverse flag

0x0000_8000
STAT_HORIZONTAL_RES2 =

Texture disable

0x0001_0000
STAT_HORIZONTAL_RES1 =

Horizontal resolution 2

0x0006_0000
STAT_VERTICAL_RES =

Horizontal resolution 1

0x0008_0000
STAT_VIDEO_MODE =

Vertical resolution (0=240, 1=480)

0x0010_0000
STAT_COLOR_DEPTH =

Video mode (0=NTSC, 1=PAL)

0x0020_0000
STAT_VERTICAL_INTERLACE =

Display color depth (0=15bit, 1=24bit)

0x0040_0000
STAT_DISPLAY_ENABLE =

Vertical interlace

0x0080_0000
STAT_IRQ =

Display enable (0=enabled, 1=disabled)

0x0100_0000
STAT_DMA_REQUEST =

IRQ flag

0x0200_0000
STAT_CMD_READY =

DMA request

0x0400_0000
STAT_VRAM_TO_CPU_READY =

Ready for command

0x0800_0000
STAT_DMA_READY =

Ready for VRAM to CPU transfer

0x1000_0000
STAT_DMA_DIRECTION =

Ready for DMA

0x6000_0000
STAT_DRAWING_ODD =

DMA direction

0x8000_0000
CMD_NOP =

GP0 command types

0x00
CMD_CLEAR_CACHE = 
0x01
CMD_FILL_RECT = 
0x02
CMD_POLY_BASE =

0x20-0x3F polygons

0x20
CMD_LINE_BASE =

0x40-0x5F lines

0x40
CMD_RECT_BASE =

0x60-0x7F rectangles

0x60
CMD_COPY_VRAM_VRAM = 
0x80
CMD_COPY_CPU_VRAM = 
0xA0
CMD_COPY_VRAM_CPU = 
0xC0
CMD_ENV_BASE =

0xE0-0xEF environment commands

0xE0

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(interrupts: nil) ⇒ GPU

Returns a new instance of GPU.



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# File 'lib/psx/gpu.rb', line 52

def initialize(interrupts: nil)
  @interrupts = interrupts

  # VRAM: 1024x512 16-bit pixels
  @vram = Array.new(VRAM_WIDTH * VRAM_HEIGHT, 0)

  # Status register
  @status = STAT_CMD_READY | STAT_DMA_READY | STAT_VRAM_TO_CPU_READY

  # Display settings
  @display_enabled = false
  @display_start_x = 0
  @display_start_y = 0
  @display_h_start = 0x200
  @display_h_end = 0xC00
  @display_v_start = 0x10
  @display_v_end = 0x100
  @video_mode = :ntsc
  @horizontal_res = 320
  @vertical_res = 240
  @color_depth_24 = false
  @interlaced = false

  # Drawing area
  @draw_area_left = 0
  @draw_area_top = 0
  @draw_area_right = 0
  @draw_area_bottom = 0
  @draw_offset_x = 0
  @draw_offset_y = 0

  # Texture settings
  @texture_page_x = 0
  @texture_page_y = 0
  @texture_depth = 0  # 0=4bit, 1=8bit, 2=15bit
  @semi_transparency = 0
  @texture_window_mask_x = 0
  @texture_window_mask_y = 0
  @texture_window_offset_x = 0
  @texture_window_offset_y = 0
  @texture_disable_allow = false

  # Mask settings
  @set_mask_bit = false
  @check_mask_bit = false

  # Command buffer for multi-word commands
  @cmd_buffer = []
  @cmd_remaining = 0
  @current_cmd = 0

  # VRAM transfer state
  @vram_transfer_x = 0
  @vram_transfer_y = 0
  @vram_transfer_start_x = 0  # Starting X for line wrap detection
  @vram_transfer_width = 0
  @vram_transfer_height = 0
  @vram_transfer_count = 0
  @vram_transfer_mode = nil  # :cpu_to_vram or :vram_to_cpu
  @vram_read_buffer = []

  # Framebuffer caching
  @framebuffer_dirty = true
  @framebuffer_cache = nil

  # DMA direction
  @dma_direction = 0

  # Interlace field (toggled by VBlank)
  @odd_field = false
end

Instance Attribute Details

#vram ⇒ Object (readonly)

Returns the value of attribute vram.



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# File 'lib/psx/gpu.rb', line 50

def vram
  @vram
end

Instance Method Details

#framebuffer ⇒ Object

Get current framebuffer as RGBA packed binary string for display Returns hash with :width, :height, :rgba (binary string) Uses caching to avoid regenerating unchanged frames



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# File 'lib/psx/gpu.rb', line 253

def framebuffer
  # Return cached framebuffer if VRAM hasn't changed
  if !@framebuffer_dirty && @framebuffer_cache &&
     @framebuffer_cache[:width] == @horizontal_res &&
     @framebuffer_cache[:height] == @vertical_res
    return @framebuffer_cache
  end

  width = @horizontal_res
  height = @vertical_res
  num_pixels = width * height

  # Build RGBA array and pack once (faster than building string)
  rgba_arr = Array.new(num_pixels * 4)
  dst_i = 0

  height.times do |y|
    vram_row = (@display_start_y + y) * VRAM_WIDTH + @display_start_x
    width.times do |x|
      color16 = @vram[vram_row + x] || 0

      # Convert 15-bit to 24-bit RGB
      rgba_arr[dst_i] = (color16 & 0x001F) << 3      # R
      rgba_arr[dst_i + 1] = (color16 & 0x03E0) >> 2  # G
      rgba_arr[dst_i + 2] = (color16 & 0x7C00) >> 7  # B
      rgba_arr[dst_i + 3] = 255                       # A
      dst_i += 4
    end
  end

  @framebuffer_dirty = false
  @framebuffer_cache = { width: width, height: height, rgba: rgba_arr.pack("C*") }
end

#gp0(value) ⇒ Object

GP0 - Rendering commands and VRAM access



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# File 'lib/psx/gpu.rb', line 155

def gp0(value)
  if @vram_transfer_mode == :cpu_to_vram
    vram_write_data(value)
    return
  end

  if @cmd_remaining > 0
    @cmd_buffer << value
    @cmd_remaining -= 1

    if @cmd_remaining == 0
      execute_gp0_command
    end
    return
  end

  cmd = (value >> 24) & 0xFF
  @current_cmd = cmd
  @cmd_buffer = [value]

  case cmd
  when CMD_NOP
    # Do nothing
  when CMD_CLEAR_CACHE
    # Clear texture cache - ignore for now
  when CMD_FILL_RECT
    @cmd_remaining = 2
  when 0x20..0x3F
    # Polygons
    @cmd_remaining = polygon_word_count(cmd) - 1
  when 0x40..0x5F
    # Lines
    @cmd_remaining = line_word_count(cmd) - 1
  when 0x60..0x7F
    # Rectangles
    @cmd_remaining = rectangle_word_count(cmd) - 1
  when CMD_COPY_VRAM_VRAM
    @cmd_remaining = 3
  when CMD_COPY_CPU_VRAM
    @cmd_remaining = 2
  when CMD_COPY_VRAM_CPU
    @cmd_remaining = 2
  when 0xE1
    gp0_draw_mode(value)
  when 0xE2
    gp0_texture_window(value)
  when 0xE3
    gp0_draw_area_top_left(value)
  when 0xE4
    gp0_draw_area_bottom_right(value)
  when 0xE5
    gp0_draw_offset(value)
  when 0xE6
    gp0_mask_settings(value)
  else
    # Unknown command - ignore
  end

  execute_gp0_command if @cmd_remaining == 0 && @cmd_buffer.length > 0
end

#gp1(value) ⇒ Object

GP1 - Display control



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# File 'lib/psx/gpu.rb', line 217

def gp1(value)
  cmd = (value >> 24) & 0xFF

  case cmd
  when 0x00
    gp1_reset
  when 0x01
    gp1_reset_command_buffer
  when 0x02
    gp1_acknowledge_irq
  when 0x03
    gp1_display_enable(value)
  when 0x04
    gp1_dma_direction(value)
  when 0x05
    gp1_display_start(value)
  when 0x06
    gp1_horizontal_range(value)
  when 0x07
    gp1_vertical_range(value)
  when 0x08
    gp1_display_mode(value)
  when 0x09
    gp1_texture_disable(value)
  when 0x10..0x1F
    gp1_gpu_info(value)
  end
end

#gp1_texture_disable(value) ⇒ Object 



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# File 'lib/psx/gpu.rb', line 246

def gp1_texture_disable(value)
  @texture_disable_allow = (value & 1) != 0
end

#mark_dirty ⇒ Object

Mark framebuffer as needing regeneration (call when VRAM is modified)



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# File 'lib/psx/gpu.rb', line 288

def mark_dirty
  @framebuffer_dirty = true
end

#read_data ⇒ Object 



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# File 'lib/psx/gpu.rb', line 146

def read_data
  if @vram_transfer_mode == :vram_to_cpu && !@vram_read_buffer.empty?
    @vram_read_buffer.shift
  else
    0
  end
end

#status ⇒ Object 



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# File 'lib/psx/gpu.rb', line 129

def status
  stat = @status

  # Update dynamic bits
  stat &= ~STAT_DISPLAY_ENABLE
  stat |= STAT_DISPLAY_ENABLE unless @display_enabled

  stat &= ~STAT_DMA_DIRECTION
  stat |= (@dma_direction << 29) & STAT_DMA_DIRECTION

  # Bit 31: Drawing odd lines in interlace mode
  stat &= ~STAT_DRAWING_ODD
  stat |= STAT_DRAWING_ODD if @odd_field

  stat
end

#vblank ⇒ Object

Called by emulator on VBlank to toggle interlace field



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# File 'lib/psx/gpu.rb', line 125

def vblank
  @odd_field = !@odd_field
end