fix: resolve relative sprite priority issues
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parent
c6e6b42869
commit
5579643d65
35
src/ppu.zig
35
src/ppu.zig
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@ -121,37 +121,36 @@ pub const Ppu = struct {
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/// Draw all relevant sprites on a scanline
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/// Draw all relevant sprites on a scanline
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fn drawSprites(self: *Self, prio: u2) void {
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fn drawSprites(self: *Self, prio: u2) void {
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// Object VRAM 3rd and 4th (0-indexed) charblocks
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const char_base = 0x4000 * 4;
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const char_base = 0x4000 * 4;
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const y = @bitCast(i8, self.vcount.scanline.read());
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const y = @bitCast(i8, self.vcount.scanline.read());
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var i: u9 = 0;
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// Loop over every fetched sprite
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while (i < width) : (i += 1) {
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sprite_loop: for (self.scanline_sprites) |maybe_sprites| {
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// Exit early if a pixel is already here
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if (maybe_sprites) |sprite| {
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if (self.scanline_buf[i] != null) continue;
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// Move on to the next sprite If its of a different priority
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if (sprite.priority() != prio) continue :sprite_loop;
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const x = i;
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for (self.scanline_sprites) |maybe_sprite| {
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if (maybe_sprite) |sprite| {
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if (sprite.priority() != prio) continue;
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var i: u9 = 0;
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px_loop: while (i < sprite.width) : (i += 1) {
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const x = (sprite.x() +% i) % 240;
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const ix = @bitCast(i9, x);
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const ix = @bitCast(i9, x);
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// If We've already rendered a pixel here don't overwrite it
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if (self.scanline_buf[x] != null) continue :px_loop;
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const start = sprite.x();
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const start = sprite.x();
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const istart = @bitCast(i9, start);
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const istart = @bitCast(i9, start);
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const end = start +% sprite.width;
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const end = start +% sprite.width;
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const iend = @bitCast(i9, end);
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const iend = @bitCast(i9, end);
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// Sprites are expected to wrap, by performing the same check on both
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// By comparing with both signed and unsigned values we ensure that sprites
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// signed and unsigned values we ensure that sprites are properly displayed
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// are displayed in all valid (AFAIK) configuration
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// in all valid scenarios
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if ((start <= x and x < end) or (istart <= ix and ix < iend)) {
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if ((start <= x and x < end) or (istart <= ix and ix < iend)) {
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self.drawSpritePixel(char_base, sprite, ix, y);
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self.drawSpritePixel(char_base, sprite, ix, y);
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}
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}
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} else break;
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}
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}
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} else break;
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}
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}
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}
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}
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@ -275,12 +274,12 @@ pub const Ppu = struct {
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0x0 => {
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0x0 => {
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const start = framebuf_pitch * @as(usize, scanline);
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const start = framebuf_pitch * @as(usize, scanline);
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self.fetchSprites();
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if (obj_enable) self.fetchSprites();
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var i: usize = 0;
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var i: usize = 0;
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while (i < 4) : (i += 1) {
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while (i < 4) : (i += 1) {
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// Draw Sprites Here
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// Draw Sprites Here
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if (obj_enable) self.drawSprites(@truncate(u2, i));
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self.drawSprites(@truncate(u2, i));
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if (i == self.bg[0].cnt.priority.read() and bg_enable & 1 == 1) self.drawBackround(0);
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if (i == self.bg[0].cnt.priority.read() and bg_enable & 1 == 1) self.drawBackround(0);
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if (i == self.bg[1].cnt.priority.read() and bg_enable >> 1 & 1 == 1) self.drawBackround(1);
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if (i == self.bg[1].cnt.priority.read() and bg_enable >> 1 & 1 == 1) self.drawBackround(1);
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if (i == self.bg[2].cnt.priority.read() and bg_enable >> 2 & 1 == 1) self.drawBackround(2);
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if (i == self.bg[2].cnt.priority.read() and bg_enable >> 2 & 1 == 1) self.drawBackround(2);
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