feat(video): add scanline rendering for background, window and sprites
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dualfroz committed
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commit
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+198
@@ -0,0 +1,198 @@
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namespace GameBoy.Video
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{
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public sealed partial class Ppu
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{
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private readonly byte[] lineBgColor = new byte[ScreenWidth];
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private void RenderScanline()
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{
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RenderBackground();
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RenderWindow();
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RenderSprites();
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}
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private void RenderBackground()
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{
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int rowBase = ly * ScreenWidth;
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bool bgEnabled = (lcdc & 0x01) != 0;
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if (!bgEnabled)
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{
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for (int x = 0; x < ScreenWidth; x++)
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{
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lineBgColor[x] = 0;
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Framebuffer[rowBase + x] = 0;
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}
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return;
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}
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int tileMapBase = (lcdc & 0x08) != 0 ? 0x1C00 : 0x1800;
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bool signed = (lcdc & 0x10) == 0;
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int y = (scy + ly) & 0xFF;
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int tileRow = y >> 3;
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int rowInTile = y & 7;
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for (int x = 0; x < ScreenWidth; x++)
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{
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int mapX = (scx + x) & 0xFF;
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int tileCol = mapX >> 3;
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int bit = 7 - (mapX & 7);
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int tileIndex = vram[tileMapBase + tileRow * 32 + tileCol];
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int tileAddr = signed
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? 0x1000 + ((sbyte)tileIndex) * 16 + rowInTile * 2
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: tileIndex * 16 + rowInTile * 2;
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int low = vram[tileAddr];
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int high = vram[tileAddr + 1];
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int color = (((high >> bit) & 1) << 1) | ((low >> bit) & 1);
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lineBgColor[x] = (byte)color;
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Framebuffer[rowBase + x] = Shade(bgp, color);
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}
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}
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private void RenderWindow()
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{
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if ((lcdc & 0x20) == 0)
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return;
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if (wy > ly)
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return;
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if (wx > 166)
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return;
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int rowBase = ly * ScreenWidth;
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int tileMapBase = (lcdc & 0x40) != 0 ? 0x1C00 : 0x1800;
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bool signed = (lcdc & 0x10) == 0;
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int winY = windowLine;
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int tileRow = winY >> 3;
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int rowInTile = winY & 7;
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int start = wx - 7;
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bool drawn = false;
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for (int x = 0; x < ScreenWidth; x++)
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{
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if (x < start)
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continue;
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drawn = true;
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int winX = x - start;
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int tileCol = winX >> 3;
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int bit = 7 - (winX & 7);
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int tileIndex = vram[tileMapBase + tileRow * 32 + tileCol];
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int tileAddr = signed
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? 0x1000 + ((sbyte)tileIndex) * 16 + rowInTile * 2
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: tileIndex * 16 + rowInTile * 2;
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int low = vram[tileAddr];
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int high = vram[tileAddr + 1];
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int color = (((high >> bit) & 1) << 1) | ((low >> bit) & 1);
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lineBgColor[x] = (byte)color;
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Framebuffer[rowBase + x] = Shade(bgp, color);
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}
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if (drawn)
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windowLine++;
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}
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private readonly int[] spriteCandidates = new int[10];
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private void RenderSprites()
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{
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if ((lcdc & 0x02) == 0)
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return;
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int height = (lcdc & 0x04) != 0 ? 16 : 8;
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int count = 0;
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for (int i = 0; i < 40 && count < 10; i++)
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{
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int spriteY = oam[i * 4] - 16;
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if (ly >= spriteY && ly < spriteY + height)
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spriteCandidates[count++] = i;
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}
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SortByPriority(count);
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int rowBase = ly * ScreenWidth;
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for (int x = 0; x < ScreenWidth; x++)
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{
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for (int c = 0; c < count; c++)
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{
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int i = spriteCandidates[c];
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int spriteX = oam[i * 4 + 1] - 8;
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if (x < spriteX || x >= spriteX + 8)
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continue;
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int attr = oam[i * 4 + 3];
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int spriteY = oam[i * 4] - 16;
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int row = ly - spriteY;
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if ((attr & 0x40) != 0)
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row = height - 1 - row;
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int tile = oam[i * 4 + 2];
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if (height == 16)
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{
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tile &= 0xFE;
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if (row >= 8)
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{
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tile += 1;
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row -= 8;
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}
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}
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int pixelCol = x - spriteX;
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int col = (attr & 0x20) != 0 ? 7 - pixelCol : pixelCol;
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int bit = 7 - col;
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int tileAddr = tile * 16 + row * 2;
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int low = vram[tileAddr];
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int high = vram[tileAddr + 1];
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int color = (((high >> bit) & 1) << 1) | ((low >> bit) & 1);
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if (color == 0)
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continue;
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bool behindBg = (attr & 0x80) != 0 && lineBgColor[x] != 0;
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if (!behindBg)
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{
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byte palette = (attr & 0x10) != 0 ? obp1 : obp0;
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Framebuffer[rowBase + x] = Shade(palette, color);
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}
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break;
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}
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}
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}
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private void SortByPriority(int count)
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{
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for (int a = 1; a < count; a++)
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{
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int key = spriteCandidates[a];
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int keyX = oam[key * 4 + 1];
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int b = a - 1;
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while (b >= 0 && ShouldSwap(spriteCandidates[b], keyX, key))
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{
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spriteCandidates[b + 1] = spriteCandidates[b];
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b--;
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}
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spriteCandidates[b + 1] = key;
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}
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}
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private bool ShouldSwap(int current, int keyX, int key)
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{
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int currentX = oam[current * 4 + 1];
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if (currentX != keyX)
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return currentX > keyX;
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return current > key;
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}
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private static byte Shade(byte palette, int color)
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{
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return (byte)((palette >> (color * 2)) & 0x03);
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}
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}
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}
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