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chore: refactor sprite rendering code

This commit is contained in:
Rekai Nyangadzayi Musuka 2022-12-27 11:51:46 -06:00
parent 1ecbbc7d29
commit 6bf1c44961
1 changed files with 22 additions and 16 deletions
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38
src/core/ppu.zig
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@ -340,6 +340,8 @@ pub const Ppu = struct {
// 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
// FIXME: Wrapping for Double-Size Sprites is not properly implemented
if (y_pos <= y and y < (y_pos + sprite_height)) {
for (self.scanline_sprites) |*maybe_sprite| {
if (maybe_sprite.* == null) {
@ -407,7 +409,7 @@ pub const Ppu = struct {
// Check to see if sprite pixel is in bounds
// TODO: Are any of the checks here redundant?
if (!(sprite_x <= x and x < (sprite_x + sprite_width))) continue;
if (sprite_x > x and x >= (sprite_x + sprite.width)) continue;
// Sprite is within bounds and therefore should be rendered
const local_x = @as(i16, x) - sprite_x;
@ -433,9 +435,6 @@ pub const Ppu = struct {
const mapping_offset = if (obj_mapping) sprite.width >> 3 else if (is_8bpp) @as(u32, 0x10) else 0x20;
const tile_offset = (tile_x >> 3) * tile_len + (tile_y >> 3) * tile_len * mapping_offset;
// TODO: This is not the proper check
// if (tile_base + tile_offset >= self.vram.buf.len) continue;
const tile = self.vram.buf[tile_base + tile_offset];
const pal_id: u16 = if (!is_8bpp) get4bppTilePalette(sprite.palBank(), col, tile) else tile;
@ -457,31 +456,36 @@ pub const Ppu = struct {
const tile_len: u32 = if (is_8bpp) 0x40 else 0x20;
const char_base = 0x4000 * 4;
const y = self.vcount.scanline.read();
var sprite_x: i16 = sprite.x();
if (sprite_x >= 240) sprite_x -= 512;
var sprite_y: i16 = sprite.y();
if (sprite_y >= 160) sprite_y -= 256;
var i: u9 = 0;
while (i < sprite.width) : (i += 1) {
const x = (sprite.x() +% i) % width;
// TODO: Something is Wrong Here
const x = @truncate(u9, @bitCast(u16, sprite_x + i));
if (x >= width) continue;
if (!shouldDrawSprite(self.bld.cnt, &self.scanline, x)) continue;
var x_pos: i32 = sprite.x();
if (x_pos >= 240) x_pos -= 512;
if (!(x_pos <= x and x < (x_pos + sprite.width))) continue;
if (sprite_x > x and x >= (sprite_x + sprite.width)) continue;
// Sprite is within bounds and therefore should be rendered
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;
const local_x = @as(i16, x) - sprite_x;
const local_y = @as(i16, y) - sprite_y;
// 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_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 tile_x = @intCast(u9, local_x) ^ if (sprite.hFlip()) (sprite.width - 1) else 0;
const tile_y = @intCast(u8, local_y) ^ if (sprite.vFlip()) (sprite.height - 1) else 0;
const row = @truncate(u3, tile_y);
const col = @truncate(u3, tile_x);
const row = @truncate(u3, tile_y);
// TODO: Finish that 2D Sprites Test ROM
const tile_base = char_base + (tile_id * 0x20) + (row * tile_row_offset) + if (is_8bpp) col else col >> 1;
@ -491,10 +495,12 @@ pub const Ppu = struct {
const tile = self.vram.buf[tile_base + tile_offset];
const pal_id: u16 = if (!is_8bpp) get4bppTilePalette(sprite.palBank(), col, tile) else tile;
const global_x = @truncate(u9, @bitCast(u16, local_x + sprite_x));
// Sprite Palette starts at 0x0500_0200
if (pal_id != 0) {
const bgr555 = self.palette.read(u16, 0x200 + pal_id * 2);
drawSpritePixel(self.bld.cnt, &self.scanline, sprite.attr0, x, bgr555);
drawSpritePixel(self.bld.cnt, &self.scanline, sprite.attr0, global_x, bgr555);
}
}
}