Files
rmg-001/src/ppu.rs
T
2021-11-05 10:08:17 -05:00

545 lines
19 KiB
Rust

use crate::utils::{
BitIndex,
get_bit,
set_bit,
};
use crate::bus::{Bus, SPRITE_ATTRIBUTE_TABLE};
use crate::cpu::{Cycles, Interrupt};
pub const LCD_WIDTH: u32 = 160;
pub const LCD_HEIGHT: u32 = 144;
pub const WIDTH: u32 = LCD_WIDTH;
pub const HEIGHT: u32 = LCD_HEIGHT;
pub const FRAME_BUFFER_LENGTH: u32 = WIDTH * HEIGHT;
pub const LCD_CONTROL_ADDRESS: u16 = 0xFF40;
pub const LCD_STATUS_ADDRESS: u16 = 0xFF41;
pub const SCROLL_Y_ADDRESS: u16 = 0xFF42;
pub const SCROLL_X_ADDRESS: u16 = 0xFF43;
pub const LCD_Y_ADDRESS: u16 = 0xFF44;
pub const LCD_Y_COMPARE_ADDRESS: u16 = 0xFF45;
pub const DMA_ADDRESS: u16 = 0xFF46;
pub const BACKGROUND_PALETTE_ADDRESS: u16 = 0xFF47;
pub const OBJECT_PALETTE_0_ADDRESS: u16 = 0xFF48;
pub const OBJECT_PALETTE_1_ADDRESS: u16 = 0xFF49;
pub const WINDOW_X_ADDRESS: u16 = 0xFF4A;
pub const WINDOW_Y_ADDRESS: u16 = 0xFF4B;
pub const TILE_MAP_ADDRESS: u16 = 0x9800;
#[derive(Debug, Copy, Clone)]
enum Pixel {
White,
Light,
Dark,
Black,
}
#[derive(Debug, Copy, Clone)]
struct ColorPalette(u8, u8, u8, u8);
#[derive(Debug, Copy, Clone)]
pub enum LCDControl {
LCDEnable,
WindowTileMapAddress,
WindowEnable,
TileAddressMode,
BackgroundTileMapAddress,
ObjectSize,
ObjectEnable,
BackgroundPriority,
}
impl LCDControl {
fn index(&self) -> BitIndex {
match self {
LCDControl::LCDEnable => BitIndex::I7,
LCDControl::WindowTileMapAddress => BitIndex::I6,
LCDControl::WindowEnable => BitIndex::I5,
LCDControl::TileAddressMode => BitIndex::I4,
LCDControl::BackgroundTileMapAddress => BitIndex::I3,
LCDControl::ObjectSize => BitIndex::I2,
LCDControl::ObjectEnable => BitIndex::I1,
LCDControl::BackgroundPriority => BitIndex::I0,
}
}
pub fn get(&self, byte: u8) -> bool {
get_bit(byte, self.index())
}
pub fn set(&self, byte: u8, val: bool) -> u8 {
set_bit(byte, val, self.index())
}
}
pub enum LCDStatusModeFlag {
HBlank,
VBlank,
SearchingOAM,
TransferringToLCD,
}
pub enum LCDStatus {
LYCInterrupt,
Mode2OAMInterrupt,
Mode1VBlankInterrupt,
Mode0HBlankInterrupt,
LYCFlag,
ModeFlag(LCDStatusModeFlag),
}
pub struct PPU {
prev_state: bool,
cycles: Cycles,
sprite_buffer: Vec<Sprite>,
}
struct Sprite {
x: u8,
y: u8,
tile_number: u8,
x_flip: bool,
y_flip: bool,
over_bg: bool,
palette_one: bool,
is_long: bool,
}
impl Sprite {
pub fn x(&self) -> u8 {
self.x
}
pub fn get_pixel(&self, lcd_x: u8, lcd_y: u8, bus: &Bus) -> Option<Pixel> {
if lcd_x < self.x.saturating_sub(8) || lcd_x >= self.x {
return None;
}
if self.over_bg {
// todo!("Implement over_bg sprite property");
}
let height: u8 = match self.is_long {
true => 16,
false => 8,
};
let x = lcd_x.saturating_sub(self.x.saturating_sub(8));
let y = lcd_y.saturating_sub(self.y .saturating_sub(16));
let x = match self.x_flip {
true => 7 - x,
false => x,
};
let y = match self.y_flip {
true => height - 1 - y,
false => y,
};
let mut tile_number = self.tile_number;
if self.is_long && x <= 7 {
tile_number = tile_number & 0xFE;
} else if self.is_long && x > 7 {
tile_number = tile_number | 0x01;
}
let tile_line = y.rem_euclid(height) * 2;
let addr = 0x8000 + (tile_number as u16 * 16) + tile_line as u16;
let tile_byte_1 = bus.read(addr);
let tile_byte_2 = bus.read(addr + 1);
let pixel_index = (x as usize).rem_euclid(8);
if PPU::get_two_bit_byte_pixels(tile_byte_1, tile_byte_2)[pixel_index] == 0 {
return None;
}
let palette = match self.palette_one {
true => bus.read(OBJECT_PALETTE_1_ADDRESS),
false => bus.read(OBJECT_PALETTE_0_ADDRESS),
};
let pixels = PPU::get_byte_pixels(tile_byte_1, tile_byte_2, palette);
Some(pixels[pixel_index])
}
}
impl PPU {
pub fn new() -> Self {
Self {
prev_state: false,
cycles: Cycles(0),
sprite_buffer: Vec::new(),
}
}
pub fn reset_cycles(&mut self) {
self.cycles.0 = 0;
}
pub fn increment_cycles(&mut self, cycles: Cycles) {
self.cycles.0 += cycles.0;
}
pub fn do_cycles(&mut self, bus: &mut Bus, cycles: Cycles, frame_buffer: &mut [u8]) {
let mut count = 0;
while count < cycles.to_t() {
self.cycle(bus, frame_buffer);
count += 1;
}
}
pub fn cycle(&mut self, bus: &mut Bus, frame_buffer: &mut [u8]) {
if !PPU::get_lcd_control(bus, LCDControl::LCDEnable) {
self.increment_cycles(Cycles(1));
return;
}
if PPU::get_lcd_y(bus) < 144 {
if self.cycles.0 == 0 {
// Mode 2 OAM scan
PPU::set_lcd_status(bus, LCDStatus::ModeFlag(LCDStatusModeFlag::SearchingOAM), true);
self.stat_interrupt(bus);
self.oam_search(bus);
} else if self.cycles.0 == 80 + 1 {
// Mode 3 drawing pixel line. This could also last 289 cycles
self.draw_line(bus, frame_buffer);
PPU::set_lcd_status(bus, LCDStatus::ModeFlag(LCDStatusModeFlag::TransferringToLCD), true);
} else if self.cycles.0 == 80 + 172 + 1 {
// Mode 0 Horizontal blank. This could last 87 or 204 cycles depending on the mode 3
PPU::set_lcd_status(bus, LCDStatus::ModeFlag(LCDStatusModeFlag::HBlank), true);
self.stat_interrupt(bus);
}
} else if PPU::get_lcd_y(bus) == 144 && self.cycles.0 == 0 {
// Mode 1 Vertical blank
bus.set_interrupt_flag(Interrupt::VBlank, true);
PPU::set_lcd_status(bus, LCDStatus::ModeFlag(LCDStatusModeFlag::VBlank), true);
self.stat_interrupt(bus);
}
self.increment_cycles(Cycles(1));
// Horizontal scan completed
if self.cycles.0 > 456 {
self.reset_cycles();
PPU::set_lcd_y(bus, PPU::get_lcd_y(bus).wrapping_add(1));
// Frame completed
if PPU::get_lcd_y(bus) > 153 {
PPU::set_lcd_y(bus, 0);
}
self.check_lyc(bus);
}
}
fn stat_interrupt(&mut self, bus: &mut Bus) {
let state = self.prev_state;
self.prev_state = (PPU::get_lcd_status(bus, LCDStatus::Mode2OAMInterrupt) && PPU::get_lcd_status(bus, LCDStatus::ModeFlag(LCDStatusModeFlag::SearchingOAM))) ||
(PPU::get_lcd_status(bus, LCDStatus::Mode0HBlankInterrupt) && PPU::get_lcd_status(bus, LCDStatus::ModeFlag(LCDStatusModeFlag::HBlank))) ||
(PPU::get_lcd_status(bus, LCDStatus::Mode1VBlankInterrupt) && PPU::get_lcd_status(bus, LCDStatus::ModeFlag(LCDStatusModeFlag::VBlank)));
if self.prev_state && !state {
bus.set_interrupt_flag(Interrupt::LCDSTAT, true);
}
}
fn check_lyc(&mut self, bus: &mut Bus) {
let lyc_compare = PPU::get_lcd_y(bus) == bus.read(LCD_Y_COMPARE_ADDRESS);
PPU::set_lcd_status(bus, LCDStatus::LYCFlag, lyc_compare);
if lyc_compare && PPU::get_lcd_status(bus, LCDStatus::LYCInterrupt) {
bus.set_interrupt_flag(Interrupt::LCDSTAT, true);
self.prev_state = true;
}
}
fn oam_search(&mut self, bus: &Bus) {
self.sprite_buffer = Vec::new();
if !PPU::get_lcd_control(bus, LCDControl::ObjectEnable) {
return;
}
let long_sprites = PPU::get_lcd_control(bus, LCDControl::ObjectSize);
let mut addr = SPRITE_ATTRIBUTE_TABLE.begin();
while addr <= SPRITE_ATTRIBUTE_TABLE.end() {
// The gameboy only supports 10 sprites per line,
// but since we are on an emulator we can avoud that limitation
if self.sprite_buffer.len() >= 10 {
todo!("Make a setting for the 10 sprites per scanline");
// break;
}
let y = bus.read(addr);
let x = bus.read(addr + 1);
if x == 0 {
addr += 4;
continue;
}
let sprite_height: u8 = match long_sprites {
true => 16,
false => 8,
};
let lcd_y = PPU::get_lcd_y(bus).saturating_add(16);
if lcd_y < y || lcd_y > (y + sprite_height - 1) {
addr += 4;
continue;
}
let tile_number = bus.read(addr + 2);
let attributes = bus.read(addr + 3);
self.sprite_buffer.push(Sprite {
x,
y,
tile_number,
is_long: long_sprites,
palette_one: get_bit(attributes, BitIndex::I4),
x_flip: get_bit(attributes, BitIndex::I5),
y_flip: get_bit(attributes, BitIndex::I6),
over_bg: get_bit(attributes, BitIndex::I7),
});
addr += 4;
}
self.sprite_buffer.sort_by(|a, b| a.x().cmp(&b.x()));
}
fn find_sprite_pixel(&self, lcd_x: u8, bus: &Bus) -> Option<Pixel> {
let lcd_y = PPU::get_lcd_y(bus);
for sprite in &self.sprite_buffer {
if let Some(pixel) = sprite.get_pixel(lcd_x, lcd_y, bus) {
return Some(pixel);
}
}
return None;
}
fn get_lcd_y(bus: &Bus) -> u8 {
bus.read(LCD_Y_ADDRESS)
}
fn set_lcd_y(bus: &mut Bus, val: u8) {
bus.force_write(LCD_Y_ADDRESS, val);
}
fn get_scroll_x(bus: &Bus) -> u8 {
bus.read(SCROLL_X_ADDRESS)
}
fn get_scroll_y(bus: &Bus) -> u8 {
bus.read(SCROLL_Y_ADDRESS)
}
fn get_window_x(bus: &Bus) -> u8 {
bus.read(WINDOW_X_ADDRESS)
}
fn get_window_y(bus: &Bus) -> u8 {
bus.read(WINDOW_Y_ADDRESS)
}
pub fn get_lcd_control(bus: &Bus, control: LCDControl) -> bool {
let byte = bus.read(LCD_CONTROL_ADDRESS);
control.get(byte)
}
pub fn get_lcd_status(bus: &Bus, status: LCDStatus) -> bool {
let byte = bus.read(LCD_STATUS_ADDRESS);
match status {
LCDStatus::LYCInterrupt => get_bit(byte, BitIndex::I6),
LCDStatus::Mode2OAMInterrupt => get_bit(byte, BitIndex::I5),
LCDStatus::Mode1VBlankInterrupt => get_bit(byte, BitIndex::I4),
LCDStatus::Mode0HBlankInterrupt => get_bit(byte, BitIndex::I3),
LCDStatus::LYCFlag => get_bit(byte, BitIndex::I2),
LCDStatus::ModeFlag(mode) => match mode {
LCDStatusModeFlag::HBlank => (byte & 0b00000011) == 0,
LCDStatusModeFlag::VBlank => (byte & 0b00000011) == 1,
LCDStatusModeFlag::SearchingOAM => (byte & 0b00000011) == 2,
LCDStatusModeFlag::TransferringToLCD => (byte & 0b00000011) == 3,
},
}
}
fn set_lcd_status(bus: &mut Bus, status: LCDStatus, val: bool) {
let mut byte = bus.read(LCD_STATUS_ADDRESS);
byte = match status {
LCDStatus::LYCInterrupt => set_bit(byte, val, BitIndex::I6),
LCDStatus::Mode2OAMInterrupt => set_bit(byte, val, BitIndex::I5),
LCDStatus::Mode1VBlankInterrupt => set_bit(byte, val, BitIndex::I4),
LCDStatus::Mode0HBlankInterrupt => set_bit(byte, val, BitIndex::I3),
LCDStatus::LYCFlag => set_bit(byte, val, BitIndex::I2),
LCDStatus::ModeFlag(mode) => match mode {
LCDStatusModeFlag::HBlank => (byte & 0b11111100) | 0,
LCDStatusModeFlag::VBlank => (byte & 0b11111100) | 1,
LCDStatusModeFlag::SearchingOAM => (byte & 0b11111100) | 2,
LCDStatusModeFlag::TransferringToLCD => (byte & 0b11111100) | 3,
},
};
bus.force_write(LCD_STATUS_ADDRESS, byte);
}
fn get_tile_bytes(x: u8, y: u8, tilemap_area: u16, default_method: bool, bus: &Bus) -> (u8, u8) {
let index_x = x as u16 / 8;
let index_y = (y as u16 / 8) * 32;
let index = index_x + index_y;
let tile_line = (y).rem_euclid(8) * 2;
let tile_number = bus.read(tilemap_area + index as u16) as u16;
let addr = if default_method {
0x8000 + tile_line as u16 + (tile_number * 16)
} else {
let tile_number = (tile_number as i8) as i16;
let tile_line = tile_line as i16;
let base = (0x9000 as u16) as i16;
(base + tile_line + (tile_number * 16)) as u16
};
(bus.read(addr), bus.read(addr + 1))
}
fn get_window_pixel(lcd_x: u8, bus: &Bus) -> Option<Pixel> {
let lcd_y = PPU::get_lcd_y(bus);
let window_x = PPU::get_window_x(bus);
let window_y = PPU::get_window_y(bus);
if !PPU::get_lcd_control(bus, LCDControl::WindowEnable) || lcd_x < (window_x.saturating_sub(7)) || window_y != lcd_y {
return None;
}
let x = lcd_x.wrapping_sub(window_x.saturating_sub(7));
let y = lcd_y.wrapping_sub(window_y);
let default_mode = PPU::get_lcd_control(bus, LCDControl::TileAddressMode);
let tilemap_area = match PPU::get_lcd_control(bus, LCDControl::WindowTileMapAddress) {
true => 0x9C00,
false => 0x9800,
};
let (tile_byte_1, tile_byte_2) = PPU::get_tile_bytes(x, y, tilemap_area, default_mode, bus);
let palette = bus.read(BACKGROUND_PALETTE_ADDRESS);
let pixels = PPU::get_byte_pixels(tile_byte_1, tile_byte_2, palette);
Some(pixels[(x as usize).rem_euclid(8)])
}
fn draw_line(&mut self, bus: &Bus, frame_buffer: &mut [u8]) {
let palette = bus.read(BACKGROUND_PALETTE_ADDRESS);
let lcd_y = PPU::get_lcd_y(bus);
if lcd_y as u32 >= LCD_HEIGHT {
return;
}
let mut lcd_x: u8 = 0;
while (lcd_x as u32) < LCD_WIDTH {
let y = lcd_y.wrapping_add(PPU::get_scroll_y(bus));
let x = lcd_x.wrapping_add(PPU::get_scroll_x(bus));
let default_mode = PPU::get_lcd_control(bus, LCDControl::TileAddressMode);
let tilemap_area = match PPU::get_lcd_control(bus, LCDControl::BackgroundTileMapAddress) {
true => 0x9C00,
false => 0x9800,
};
let (tile_byte_1, tile_byte_2) = PPU::get_tile_bytes(x, y, tilemap_area, default_mode, bus);
let bg_pixels = PPU::get_byte_pixels(tile_byte_1, tile_byte_2, palette);
let idx = (lcd_x as usize + (lcd_y as usize * LCD_WIDTH as usize)) * 4;
let pixel = bg_pixels[x.rem_euclid(8) as usize];
let rgba = PPU::get_rgba(pixel);
frame_buffer[idx] = rgba[0];
frame_buffer[idx + 1] = rgba[1];
frame_buffer[idx + 2] = rgba[2];
if let Some(window_pixel) = PPU::get_window_pixel(lcd_x, bus) {
let rgba = PPU::get_rgba(window_pixel);
frame_buffer[idx] = rgba[0];
frame_buffer[idx + 1] = rgba[1];
frame_buffer[idx + 2] = rgba[2];
}
if let Some(sprite_pixel) = self.find_sprite_pixel(lcd_x, bus) {
let rgba = PPU::get_rgba(sprite_pixel);
frame_buffer[idx] = rgba[0];
frame_buffer[idx + 1] = rgba[1];
frame_buffer[idx + 2] = rgba[2];
}
lcd_x += 1;
/* for pixel in bg_pixels {
let idx = (lcd_x as usize + (lcd_y as usize * LCD_WIDTH as usize)) * 4;
let rgba = PPU::get_rgba(pixel);
frame_buffer[idx] = rgba[0];
frame_buffer[idx + 1] = rgba[1];
frame_buffer[idx + 2] = rgba[2];
if let Some(window_pixel) = PPU::get_window_pixel(lcd_x, bus) {
let rgba = PPU::get_rgba(pixel);
frame_buffer[idx] = rgba[0];
frame_buffer[idx + 1] = rgba[1];
frame_buffer[idx + 2] = rgba[2];
}
lcd_x += 1;
} */
}
}
fn get_palette(index: u8, palette_byte: u8) -> u8 {
match index {
0b00 => palette_byte & 0b11,
0b01 => (palette_byte >> 2) & 0b11,
0b10 => (palette_byte >> 4) & 0b11,
0b11 => (palette_byte >> 6) & 0b11,
_ => unreachable!(),
}
}
fn get_pixel(two_bit_pixel: u8) -> Pixel {
match two_bit_pixel {
0b00 => Pixel::White,
0b01 => Pixel::Light,
0b10 => Pixel::Dark,
0b11 => Pixel::Black,
_ => unreachable!(),
}
}
fn get_rgba(pixel: Pixel) -> [u8; 4] {
match pixel {
Pixel::White => [255, 255, 255, 0],
Pixel::Light => [192, 192, 192, 0],
Pixel::Dark => [81, 81, 81, 0],
Pixel::Black => [0, 0, 0, 0],
}
}
fn get_two_bit_byte_pixels(byte1: u8, byte2: u8) -> [u8; 8] {
[
((byte1 >> 7) & 0b01) | ((byte2 >> 6) & 0b10),
((byte1 >> 6) & 0b01) | ((byte2 >> 5) & 0b10),
((byte1 >> 5) & 0b01) | ((byte2 >> 4) & 0b10),
((byte1 >> 4) & 0b01) | ((byte2 >> 3) & 0b10),
((byte1 >> 3) & 0b01) | ((byte2 >> 2) & 0b10),
((byte1 >> 2) & 0b01) | ((byte2 >> 1) & 0b10),
((byte1 >> 1) & 0b01) | (byte2 & 0b10),
(byte1 & 0b01) | ((byte2 << 1) & 0b10),
]
}
fn get_byte_pixels(byte1: u8, byte2: u8, palette: u8) -> [Pixel; 8] {
[
PPU::get_pixel(PPU::get_palette(((byte1 >> 7) & 0b01) | ((byte2 >> 6) & 0b10), palette)),
PPU::get_pixel(PPU::get_palette(((byte1 >> 6) & 0b01) | ((byte2 >> 5) & 0b10), palette)),
PPU::get_pixel(PPU::get_palette(((byte1 >> 5) & 0b01) | ((byte2 >> 4) & 0b10), palette)),
PPU::get_pixel(PPU::get_palette(((byte1 >> 4) & 0b01) | ((byte2 >> 3) & 0b10), palette)),
PPU::get_pixel(PPU::get_palette(((byte1 >> 3) & 0b01) | ((byte2 >> 2) & 0b10), palette)),
PPU::get_pixel(PPU::get_palette(((byte1 >> 2) & 0b01) | ((byte2 >> 1) & 0b10), palette)),
PPU::get_pixel(PPU::get_palette(((byte1 >> 1) & 0b01) | (byte2 & 0b10), palette)),
PPU::get_pixel(PPU::get_palette((byte1 & 0b01) | ((byte2 << 1) & 0b10), palette)),
]
}
}