From 5d3435757cf7aaf98ef36b9afd71f7c698f734ea Mon Sep 17 00:00:00 2001 From: Rekai Musuka Date: Wed, 2 Nov 2022 10:40:07 -0300 Subject: [PATCH] chore: improve readability of sprite drawing code a bit --- src/core/ppu.zig | 58 ++++++++++++++++++------------------------------ 1 file changed, 21 insertions(+), 37 deletions(-) diff --git a/src/core/ppu.zig b/src/core/ppu.zig index e57ea90..d7135ee 100644 --- a/src/core/ppu.zig +++ b/src/core/ppu.zig @@ -263,8 +263,7 @@ pub const Ppu = struct { scanline: Scanline, pub fn init(allocator: Allocator, sched: *Scheduler) !Self { - // Queue first Hblank - sched.push(.Draw, 240 * 4); + sched.push(.Draw, 240 * 4); // Add first PPU Event to Scheduler const sprites = try allocator.create([128]?Sprite); std.mem.set(?Sprite, sprites, null); @@ -324,20 +323,16 @@ pub const Ppu = struct { // Only consider enabled Sprites if (attr0.is_affine.read() or !attr0.disabled.read()) { const attr1 = @bitCast(Attr1, self.oam.read(u16, i + 2)); + const sprite_height = spriteDimensions(attr0.shape.read(), attr1.size.read())[1]; // When fetching sprites we only care about ones that could be rendered // on this scanline - const iy = @bitCast(i8, y); - - const start = attr0.y.read(); - const istart = @bitCast(i8, start); - - const end = start +% spriteDimensions(attr0.shape.read(), attr1.size.read())[1]; - const iend = @bitCast(i8, end); + var y_pos: i32 = attr0.y.read(); + if (y_pos >= 160) y_pos -= 256; // fleroviux's solution to negative positions // Sprites are expected to be able to wraparound, we perform the same check // for unsigned and signed values so that we handle all valid sprite positions - if ((start <= y and y < end) or (istart <= iy and iy < iend)) { + if (y_pos <= y and y < (y_pos + sprite_height)) { for (self.scanline_sprites) |*maybe_sprite| { if (maybe_sprite.* == null) { maybe_sprite.* = Sprite.init(attr0, attr1, @bitCast(Attr2, self.oam.read(u16, i + 4))); @@ -364,8 +359,6 @@ pub const Ppu = struct { } fn drawAffineSprite(self: *Self, sprite: AffineSprite) void { - const iy = @bitCast(i8, self.vcount.scanline.read()); - const is_8bpp = sprite.is8bpp(); const tile_id: u32 = sprite.tileId(); const obj_mapping = self.dispcnt.obj_mapping.read(); @@ -374,25 +367,22 @@ pub const Ppu = struct { const char_base = 0x4000 * 4; + const y = self.vcount.scanline.read(); + var i: u9 = 0; while (i < sprite.width) : (i += 1) { const x = (sprite.x() +% i) % width; - const ix = @bitCast(i9, x); - if (!shouldDrawSprite(self.bld.cnt, &self.scanline, x)) continue; - const sprite_start = sprite.x(); - const isprite_start = @bitCast(i9, sprite_start); - const sprite_end = sprite_start +% sprite.width; - const isprite_end = @bitCast(i9, sprite_end); + var x_pos: i32 = sprite.x(); + if (x_pos >= 240) x_pos -= 512; - const condition = (sprite_start <= x and x < sprite_end) or (isprite_start <= ix and ix < isprite_end); - if (!condition) continue; + if (!(x_pos <= x and x < (x_pos + sprite.width))) continue; // Sprite is within bounds and therefore should be rendered // std.math.absInt is branchless - const tile_x = @bitCast(u9, std.math.absInt(ix - @bitCast(i9, sprite.x())) catch unreachable); - const tile_y = @bitCast(u8, std.math.absInt(iy -% @bitCast(i8, sprite.y())) catch unreachable); + const tile_x = @bitCast(u32, @as(i32, std.math.absInt(@as(i32, x) - x_pos) catch unreachable)); + const tile_y = @bitCast(u32, @as(i32, std.math.absInt(@bitCast(i8, y) -% @bitCast(i8, sprite.y())) catch unreachable)); const row = @truncate(u3, tile_y); const col = @truncate(u3, tile_x); @@ -414,8 +404,6 @@ pub const Ppu = struct { } fn drawSprite(self: *Self, sprite: Sprite) void { - const iy = @bitCast(i8, self.vcount.scanline.read()); - const is_8bpp = sprite.is8bpp(); const tile_id: u32 = sprite.tileId(); const obj_mapping = self.dispcnt.obj_mapping.read(); @@ -424,31 +412,27 @@ pub const Ppu = struct { const char_base = 0x4000 * 4; + const y = self.vcount.scanline.read(); + var i: u9 = 0; while (i < sprite.width) : (i += 1) { const x = (sprite.x() +% i) % width; - const ix = @bitCast(i9, x); - if (!shouldDrawSprite(self.bld.cnt, &self.scanline, x)) continue; - const sprite_start = sprite.x(); - const isprite_start = @bitCast(i9, sprite_start); - const sprite_end = sprite_start +% sprite.width; - const isprite_end = @bitCast(i9, sprite_end); + var x_pos: i32 = sprite.x(); + if (x_pos >= 240) x_pos -= 512; - const condition = (sprite_start <= x and x < sprite_end) or (isprite_start <= ix and ix < isprite_end); - if (!condition) continue; + if (!(x_pos <= x and x < (x_pos + sprite.width))) continue; // Sprite is within bounds and therefore should be rendered - // std.math.absInt is branchless - const x_diff = @bitCast(u9, std.math.absInt(ix - @bitCast(i9, sprite.x())) catch unreachable); - const y_diff = @bitCast(u8, std.math.absInt(iy -% @bitCast(i8, sprite.y())) catch unreachable); + const x_diff: i32 = std.math.absInt(@as(i32, x) - x_pos) catch unreachable; + const y_diff: i32 = std.math.absInt(@bitCast(i8, y) -% @bitCast(i8, sprite.y())) catch unreachable; // Note that we flip the tile_pos not the (tile_pos % 8) like we do for // Background Tiles. By doing this we mirror the entire sprite instead of // just a specific tile (see how sprite.width and sprite.height are involved) - const tile_y = y_diff ^ if (sprite.vFlip()) (sprite.height - 1) else 0; - const tile_x = x_diff ^ if (sprite.hFlip()) (sprite.width - 1) else 0; + const tile_x = @intCast(u9, x_diff) ^ if (sprite.hFlip()) (sprite.width - 1) else 0; + const tile_y = @intCast(u8, y_diff) ^ if (sprite.vFlip()) (sprite.height - 1) else 0; const row = @truncate(u3, tile_y); const col = @truncate(u3, tile_x);