private void EvaluateSprites()
{
for (int i = 0; i < spritesNumber; ++i)
{
currentScanlineSprites[i].Reset();
}
spritesNumber = 0;
spriteZeroSelected = false;
statusRegister.SpriteOverflow = false;
// decide which sprites are visible on current scanline
for (int i = 0; i < 64; ++i)
{
ObjectAttributeEntry currentSprite = Oam.EntryAt(i);
int diff = scanLine - currentSprite.Y;
if (diff >= 0 && diff < (controlRegister.SpriteSize ? 16 : 8))
{
if (spritesNumber == 8)
{
statusRegister.SpriteOverflow = true;
break;
}
// clone because we are modifying X value in each cycle
currentScanlineSprites[spritesNumber++] = currentSprite.Clone() as ObjectAttributeEntry;
// sprite zero is in current scanline
if (i == 0)
{
spriteZeroSelected = true;
}
}
}
}
public Ppu()
{
for (int i = 0; i < 8; ++i)
{
currentScanlineSprites[i] = new ObjectAttributeEntry();
}
}
public void Reset()
{
fineX = 0;
toggle = false;
internalBuffer = 0;
scanLine = 0;
cycle = 0;
FrameComplete = false;
bgNextTileId = 0;
bgNextTileAttribute = 0;
bgNextTileLsb = 0;
bgNextTileMsb = 0;
bgPatternLow.Register = 0;
bgPatternHigh.Register = 0;
bgAttributeLow.Register = 0;
bgAttributeHigh.Register = 0;
vRam.Register = 0;
tRam.Register = 0;
controlRegister.Register = 0;
maskRegister.Register = 0;
statusRegister.Register = 0;
for (int i = 0; i < 8; ++i)
{
currentScanlineSprites[i] = new ObjectAttributeEntry();
}
spriteZeroSelected = false;
spriteZeroRendered = false;
}