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feat: implement object blending

This commit is contained in:
Rekai Nyangadzayi Musuka 2022-06-23 02:31:34 -03:00
parent 02534c5c19
commit 265234ee97
1 changed files with 39 additions and 27 deletions
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66
src/ppu.zig
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@ -164,7 +164,7 @@ pub const Ppu = struct {
const x = (sprite.x() +% i) % width; const x = (sprite.x() +% i) % width;
const ix = @bitCast(i9, x); const ix = @bitCast(i9, x);
if (self.scanline.top()[x] != null) continue; if (!shouldDrawSprite(self.bldcnt, &self.scanline, x)) continue;
const sprite_start = sprite.x(); const sprite_start = sprite.x();
const isprite_start = @bitCast(i9, sprite_start); const isprite_start = @bitCast(i9, sprite_start);
@ -191,7 +191,10 @@ pub const Ppu = struct {
const pal_id: u16 = if (!is_8bpp) get4bppTilePalette(sprite.palBank(), col, tile) else tile; const pal_id: u16 = if (!is_8bpp) get4bppTilePalette(sprite.palBank(), col, tile) else tile;
// Sprite Palette starts at 0x0500_0200 // Sprite Palette starts at 0x0500_0200
if (pal_id != 0) self.scanline.top()[x] = self.palette.read(u16, 0x200 + pal_id * 2); if (pal_id != 0) {
const bgr555 = self.palette.read(u16, 0x200 + pal_id * 2);
copyToSpriteBuffer(self.bldcnt, &self.scanline, x, bgr555);
}
} }
} }
@ -211,15 +214,7 @@ pub const Ppu = struct {
const x = (sprite.x() +% i) % width; const x = (sprite.x() +% i) % width;
const ix = @bitCast(i9, x); const ix = @bitCast(i9, x);
if (self.scanline.top()[x] != null) continue; if (!shouldDrawSprite(self.bldcnt, &self.scanline, x)) continue;
if (self.scanline.btm()[x] != null) {
if (self.bldcnt.mode.read() != 0b01) continue;
const b_layers = self.bldcnt.layer_b.read();
const is_blend_enabled = (b_layers >> 4) & 1 == 1;
if (!is_blend_enabled) continue;
}
const sprite_start = sprite.x(); const sprite_start = sprite.x();
const isprite_start = @bitCast(i9, sprite_start); const isprite_start = @bitCast(i9, sprite_start);
@ -254,19 +249,7 @@ pub const Ppu = struct {
// Sprite Palette starts at 0x0500_0200 // Sprite Palette starts at 0x0500_0200
if (pal_id != 0) { if (pal_id != 0) {
const bgr555 = self.palette.read(u16, 0x200 + pal_id * 2); const bgr555 = self.palette.read(u16, 0x200 + pal_id * 2);
copyToSpriteBuffer(self.bldcnt, &self.scanline, x, bgr555);
if (self.bldcnt.mode.read() == 0b01) {
// Alpha Blending
const a_layers = self.bldcnt.layer_a.read();
const is_blend_enabled = (a_layers >> 4) & 1 == 1;
if (is_blend_enabled) {
self.scanline.btm()[x] = bgr555;
return;
}
}
self.scanline.top()[x] = bgr555;
} }
} }
} }
@ -312,7 +295,7 @@ pub const Ppu = struct {
if (pal_id != 0) { if (pal_id != 0) {
const bgr555 = self.palette.read(u16, pal_id * 2); const bgr555 = self.palette.read(u16, pal_id * 2);
drawToScanlineBuffer(n, self.bldcnt, &self.scanline, i, bgr555); copyToBackgroundBuffer(n, self.bldcnt, &self.scanline, i, bgr555);
} }
} }
@ -369,7 +352,7 @@ pub const Ppu = struct {
if (pal_id != 0) { if (pal_id != 0) {
const bgr555 = self.palette.read(u16, pal_id * 2); const bgr555 = self.palette.read(u16, pal_id * 2);
drawToScanlineBuffer(n, self.bldcnt, &self.scanline, i, bgr555); copyToBackgroundBuffer(n, self.bldcnt, &self.scanline, i, bgr555);
} }
} }
} }
@ -1110,7 +1093,21 @@ fn shouldDrawBackground(comptime n: u2, bldcnt: io.BldCnt, scanline: *Scanline,
return true; return true;
} }
fn drawToScanlineBuffer(comptime n: u2, bldcnt: io.BldCnt, scanline: *Scanline, i: usize, bgr555: u16) void { fn shouldDrawSprite(bldcnt: io.BldCnt, scanline: *Scanline, x: u9) bool {
if (scanline.top()[x] != null) return false;
if (scanline.btm()[x] != null) {
if (bldcnt.mode.read() != 0b01) return false;
const b_layers = bldcnt.layer_b.read();
const is_blend_enabled = (b_layers >> 4) & 1 == 1;
if (!is_blend_enabled) return false;
}
return true;
}
fn copyToBackgroundBuffer(comptime n: u2, bldcnt: io.BldCnt, scanline: *Scanline, i: usize, bgr555: u16) void {
if (bldcnt.mode.read() == 0b01) { if (bldcnt.mode.read() == 0b01) {
// Standard Alpha Blending // Standard Alpha Blending
const a_layers = bldcnt.layer_a.read(); const a_layers = bldcnt.layer_a.read();
@ -1127,6 +1124,21 @@ fn drawToScanlineBuffer(comptime n: u2, bldcnt: io.BldCnt, scanline: *Scanline,
scanline.top()[i] = bgr555; scanline.top()[i] = bgr555;
} }
fn copyToSpriteBuffer(bldcnt: io.BldCnt, scanline: *Scanline, x: u9, bgr555: u16) void {
if (bldcnt.mode.read() == 0b01) {
// Alpha Blending
const a_layers = bldcnt.layer_a.read();
const is_blend_enabled = (a_layers >> 4) & 1 == 1;
if (is_blend_enabled) {
scanline.btm()[x] = bgr555;
return;
}
}
scanline.top()[x] = bgr555;
}
const Scanline = struct { const Scanline = struct {
const Self = @This(); const Self = @This();