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Sprite 0 Hit, Background/Sprite masks (left-most 8 pixels)

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This commit is contained in:
Souryo 2014-06-21 12:42:40 -04:00
parent 95abc2f371
commit 1def59c730
2 changed files with 74 additions and 16 deletions
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79
Core/PPU.cpp
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@ -275,7 +275,9 @@ void PPU::LoadSpriteTileInfo(uint8_t spriteIndex)
uint8_t tileIndex = _secondarySpriteRAM[spriteAddr+1];
uint8_t attributes = _secondarySpriteRAM[spriteAddr+2];
uint8_t spriteX = _secondarySpriteRAM[spriteAddr+3];
bool backgroundPriority = (attributes & 0x20) == 0x20;
bool horizontalMirror = (attributes & 0x40) == 0x40;
bool verticalMirror = (attributes & 0x80) == 0x80;
if(spriteY < 240 && spriteY == _spriteRAM[63 * 4] && tileIndex == 0xFF && attributes == 0xFF && spriteX == 0xFF) {
//Skip this sprite
@ -284,13 +286,25 @@ void PPU::LoadSpriteTileInfo(uint8_t spriteIndex)
if(spriteY < 240) {
uint16_t tileAddr;
if(_flags.LargeSprites) {
throw exception("Not implemented yet");
uint8_t lineOffset;
if(verticalMirror) {
if(_flags.LargeSprites) {
//TODO: Is this ok for large sprites?
std::cout << "TODO";
}
lineOffset = (_flags.LargeSprites ? 15 : 7) - (_scanline - spriteY);
} else {
tileAddr = ((tileIndex << 4) | _flags.SpritePatternAddr) + (_scanline - spriteY);
lineOffset = _scanline - spriteY;
}
if(_flags.LargeSprites) {
tileAddr = ((tileIndex & 0x01) ? 0x1000 : 0x0000) | (tileIndex & ~0x01) + lineOffset;
} else {
tileAddr = ((tileIndex << 4) | _flags.SpritePatternAddr) + lineOffset;
}
_spriteX[spriteIndex] = spriteX;
_spriteTiles[spriteIndex].BackgroundPriority = backgroundPriority;
_spriteTiles[spriteIndex].HorizontalMirror = horizontalMirror;
_spriteTiles[spriteIndex].PaletteOffset = (attributes & 0x03) << 2;
_spriteTiles[spriteIndex].LowByte = _memoryManager->ReadVRAM(tileAddr);
@ -324,16 +338,17 @@ void PPU::ShiftTileRegisters()
void PPU::DrawPixel()
{
//This is called 3.7 million times per second - needs to be as fast as possible.
bool useBackground = true;
uint32_t pixelColor = 0;
uint8_t offset = _state.XScroll;
uint32_t offset = _state.XScroll;
bool useBackground = true;
uint32_t backgroundColor = (((_state.LowBitShift << offset) & 0x8000) >> 15) | (((_state.HighBitShift << offset) & 0x8000) >> 14);
uint32_t spriteColor = 0;
for(int i = 0; i < 8; i++) {
uint8_t i;
for(i = 0; i < 8; i++) {
int32_t shift = -((int32_t)_spriteX[i] - (int32_t)_cycle + 1);
if(shift >= 0 && shift < 8) {
uint32_t spriteColor;
if(_spriteTiles[i].HorizontalMirror) {
spriteColor = ((_spriteTiles[i].LowByte >> shift) & 0x01) | ((_spriteTiles[i].HighByte >> shift) & 0x01) << 1;
} else {
@ -341,20 +356,46 @@ void PPU::DrawPixel()
}
if(spriteColor != 0) {
pixelColor = 0xFF000000 | PPU_PALETTE_RGB[GetSpritePaletteEntry(_spriteTiles[i].PaletteOffset, spriteColor)];
useBackground = false;
//First sprite without a 00 color, use it.
break;
}
}
}
if(useBackground) {
// If we're grabbing the pixel from the high part of the shift register, use the previous tile's palette, not the current one
pixelColor = 0xFF000000 | PPU_PALETTE_RGB[GetBGPaletteEntry(offset < 8 ? _previousTile.PaletteOffset : _currentTile.PaletteOffset, backgroundColor)];
if(_cycle <= 8) {
if(!_flags.BackgroundMask) {
//"0: Hide background in leftmost 8 pixels of screen;"
backgroundColor = 0;
}
if(!_flags.SpriteMask) {
//"0: Hide sprites in leftmost 8 pixels of screen;"
spriteColor = 0;
}
}
if(spriteColor != 0 && (backgroundColor == 0 || !_spriteTiles[i].BackgroundPriority)) {
//Check sprite priority
useBackground = false;
}
if(i == 0 && spriteColor != 0 && backgroundColor != 0 && _sprite0Visible && _cycle != 256 && _flags.BackgroundEnabled && _flags.SpritesEnabled) {
//"The hit condition is basically sprite zero is in range AND the first sprite output unit is outputting a non-zero pixel AND the background drawing unit is outputting a non-zero pixel."
//"Sprite zero hits do not register at x=255" (cycle 256)
//"... provided that background and sprite rendering are both enabled"
//"Should always miss when Y >= 239"
_statusFlags.Sprite0Hit = true;
}
uint32_t pixelColor = 0;
if(useBackground) {
// If we're grabbing the pixel from the high part of the shift register, use the previous tile's palette, not the current one
pixelColor = PPU_PALETTE_RGB[GetBGPaletteEntry(offset < 8 ? _previousTile.PaletteOffset : _currentTile.PaletteOffset, backgroundColor)];
} else {
pixelColor = PPU_PALETTE_RGB[GetSpritePaletteEntry(_spriteTiles[i].PaletteOffset, spriteColor)];
}
uint32_t bufferPosition = _scanline * 256 + (_cycle - 1);
((uint32_t*)_outputBuffer)[bufferPosition] = pixelColor;
((uint32_t*)_outputBuffer)[bufferPosition] = 0xFF000000 | pixelColor;
//Shift the tile registers to prepare for the next cycle
ShiftTileRegisters();
@ -448,11 +489,15 @@ void PPU::CopyOAMData()
static uint8_t _buffer = 0;
static bool _writeData = false;
static bool _done = false;
static bool _sprite0Added = true;
if(_cycle >= 65 && _cycle <= 256) {
if(_cycle == 65) {
_sprite0Added = false;
_secondaryOAMAddr = 0;
_done = false;
} else if(_cycle == 256) {
_sprite0Visible = _sprite0Added;
}
if(_state.SpriteRamAddr >= 0x100) {
@ -476,6 +521,10 @@ void PPU::CopyOAMData()
if(_writeData) {
_secondaryOAMAddr++;
if(_state.SpriteRamAddr == 0x01) {
_sprite0Added = true;
}
if((_secondaryOAMAddr & 0x03) == 0) {
//Done copying
_writeData = false;

11
Core/PPU.h
View file

@ -59,11 +59,19 @@ struct PPUState
};
struct TileInfo
{
uint8_t LowByte;
uint8_t HighByte;
uint8_t PaletteOffset;
};
struct SpriteInfo
{
uint8_t LowByte;
uint8_t HighByte;
uint8_t PaletteOffset;
bool HorizontalMirror;
bool BackgroundPriority;
};
class PPU : public IMemoryHandler
@ -97,7 +105,8 @@ class PPU : public IMemoryHandler
TileInfo _previousTile;
int32_t _spriteX[8];
TileInfo _spriteTiles[8];
SpriteInfo _spriteTiles[8];
bool _sprite0Visible = false;
void UpdateStatusFlag();