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fix(ppu): ensure better timings for sprite fetcher

This commit is contained in:
Rekai Nyangadzayi Musuka 2021-04-20 03:14:00 -05:00
parent db1b40fe2d
commit 4f4c867a63
1 changed files with 73 additions and 68 deletions
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141
src/ppu.rs
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@ -168,45 +168,45 @@ impl Ppu {
fn draw(&mut self, cycle: u32) { fn draw(&mut self, cycle: u32) {
use FetcherState::*; use FetcherState::*;
let control = &self.control;
let pos = &self.pos;
// By only running on odd cycles, we can ensure that we draw every two T cycles let line_y = self.pos.line_y;
if cycle % 2 != 0 { let window_y = self.pos.window_y;
let control = &self.control; let is_window = self.control.window_enabled() && window_y <= line_y;
let pos = &self.pos;
let line_y = self.pos.line_y; // Determine whether we need to enable sprite fetching
let window_y = self.pos.window_y; let mut obj_attr = None;
let is_window = self.control.window_enabled() && window_y <= line_y;
// Determine whether we need to enable sprite fetching for i in 0..self.obj_buffer.len() {
let mut obj_attr = None; if let Some(attr) = self.obj_buffer.get(i) {
for i in 0..self.obj_buffer.len() { if attr.x <= (self.x_pos + 8) {
if let Some(attr) = self.obj_buffer.get(i) { // self.fetcher.obj.resume(); TODO: Try running only when there's a sprite
if attr.x <= (self.x_pos + 8) { self.fetcher.bg.reset();
// self.fetcher.obj.resume(); TODO: Try running only when there's a sprite self.fetcher.bg.pause();
self.fetcher.bg.reset(); self.fifo.pause();
self.fetcher.bg.pause();
self.fifo.pause();
obj_attr = Some(attr); obj_attr = Some(attr);
}
} }
} }
}
if let Some(attr) = obj_attr { if let Some(attr) = obj_attr {
// Run the Object Fetcher match self.fetcher.obj.state {
let obj_size = match self.control.obj_size() { TileNumber => {
ObjectSize::EightByEight => 8, if cycle % 2 != 0 {
ObjectSize::EightBySixteen => 16,
};
match self.fetcher.obj.state {
TileNumber => {
self.fetcher.obj.tile.with_id(attr.tile_index); self.fetcher.obj.tile.with_id(attr.tile_index);
self.fetcher.obj.next(TileDataLow); self.fetcher.obj.next(TileDataLow);
} }
TileDataLow => { }
TileDataLow => {
if cycle % 2 != 0 {
let obj_size = match self.control.obj_size() {
ObjectSize::EightByEight => 8,
ObjectSize::EightBySixteen => 16,
};
let addr = PixelFetcher::get_obj_low_addr(attr, &self.pos, obj_size); let addr = PixelFetcher::get_obj_low_addr(attr, &self.pos, obj_size);
let byte = self.read_byte(addr); let byte = self.read_byte(addr);
@ -214,7 +214,14 @@ impl Ppu {
self.fetcher.obj.next(TileDataHigh); self.fetcher.obj.next(TileDataHigh);
} }
TileDataHigh => { }
TileDataHigh => {
if cycle % 2 != 0 {
let obj_size = match self.control.obj_size() {
ObjectSize::EightByEight => 8,
ObjectSize::EightBySixteen => 16,
};
let addr = PixelFetcher::get_obj_low_addr(attr, &self.pos, obj_size); let addr = PixelFetcher::get_obj_low_addr(attr, &self.pos, obj_size);
let byte = self.read_byte(addr + 1); let byte = self.read_byte(addr + 1);
@ -222,55 +229,57 @@ impl Ppu {
self.fetcher.obj.next(SendToFifo); self.fetcher.obj.next(SendToFifo);
} }
SendToFifo => { }
self.fetcher.obj.fifo_count += 1; SendToFifo => {
self.fetcher.obj.fifo_count += 1;
if self.fetcher.obj.fifo_count == 1 { if self.fetcher.obj.fifo_count == 1 {
// Load into fifo // Load into Fifo
let tile_bytes = let tile_bytes = self.fetcher.obj.tile.low.zip(self.fetcher.obj.tile.high);
self.fetcher.obj.tile.low.zip(self.fetcher.obj.tile.high);
if let Some(bytes) = tile_bytes { if let Some(bytes) = tile_bytes {
let low = bytes.0; let low = bytes.0;
let high = bytes.1; let high = bytes.1;
let pixel = TwoBitsPerPixel::from_bytes(high, low); let pixel = TwoBitsPerPixel::from_bytes(high, low);
let palette = match attr.flags.palette() { let palette = match attr.flags.palette() {
ObjectPaletteId::Palette0 => self.monochrome.obj_palette_0, ObjectPaletteId::Palette0 => self.monochrome.obj_palette_0,
ObjectPaletteId::Palette1 => self.monochrome.obj_palette_1, ObjectPaletteId::Palette1 => self.monochrome.obj_palette_1,
};
let num_to_add = 8 - self.fifo.object.len();
for i in 0..num_to_add {
let bit = 7 - i;
let priority = attr.flags.priority();
let shade = palette.colour(pixel.pixel(bit));
let fifo_pixel = ObjectFifoPixel {
shade,
palette,
priority,
}; };
let num_to_add = 8 - self.fifo.object.len(); self.fifo.object.push_back(fifo_pixel);
for i in 0..num_to_add {
let bit = 7 - i;
let priority = attr.flags.priority();
let shade = palette.colour(pixel.pixel(bit));
let fifo_pixel = ObjectFifoPixel {
shade,
palette,
priority,
};
self.fifo.object.push_back(fifo_pixel);
}
} }
} else if self.fetcher.obj.fifo_count == 2 {
self.fetcher.bg.resume(); self.fetcher.bg.resume();
self.fifo.resume(); self.fifo.resume();
self.fetcher.obj.reset();
} else {
panic!("Rekai Musuka <rekai@musuka.dev> is a bad programmer");
} }
} else if self.fetcher.obj.fifo_count == 2 {
self.fetcher.obj.reset();
} else {
panic!("Object FIFO Logic Error has occurred :angry:");
} }
} }
} }
}
// By only running on odd cycles, we can ensure that we draw every two T cycles
if cycle % 2 != 0 {
if self.fetcher.bg.is_enabled() { if self.fetcher.bg.is_enabled() {
match self.fetcher.bg.state { match self.fetcher.bg.state {
TileNumber => { TileNumber => {
@ -316,8 +325,6 @@ impl Ppu {
self.fetcher.bg.next(TileNumber); self.fetcher.bg.next(TileNumber);
} }
} }
} else {
self.fetcher.bg.resume();
} }
} }
@ -339,8 +346,6 @@ impl Ppu {
self.x_pos += 1; self.x_pos += 1;
} }
} else {
self.fifo.resume();
} }
} }