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new ppu: sprite priority and left 8 pixel enable/disable rendering support

This commit is contained in:
zeromus 2008-08-18 06:03:27 +00:00
parent 86754e3b21
commit 7d7f5ad468
1 changed files with 24 additions and 4 deletions
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28
src/ppu.cpp
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@ -50,6 +50,9 @@
#define ScreenON (PPU[1]&0x08) //Show screen
#define PPUON (PPU[1]&0x18) //PPU should operate
#define SpriteLeft8 (PPU[1]&0x04)
#define BGLeft8 (PPU[1]&0x02)
#define PPU_status (PPU[2])
#define Pal (PALRAM)
@ -1871,6 +1874,11 @@ int FCEUX_PPU_Loop(int skip) {
uint8 *target=XBuf+(yp<<8)+xstart;
uint8 *ptr = target;
int rasterpos = xstart;
//check all the conditions that can cause things to render in these 8px
bool renderspritenow = SpriteON && rendersprites && (xt>0 || SpriteLeft8);
bool renderbgnow = ScreenON && renderbg && (xt>0 || BGLeft8);
for(int xp=0;xp<8;xp++,rasterpos++) {
//bg pos is different from raster pos due to its offsetability.
@ -1879,10 +1887,10 @@ int FCEUX_PPU_Loop(int skip) {
int bgpx = bgpos&7;
int bgtile = bgpos>>3;
//generate the BG data
uint8 pixel=0, pixelcolor;
if(ScreenON && renderbg)
//generate the BG data
if(renderbgnow)
{
uint8* pt = bgdata.main[bgtile].pt;
pixel = ((pt[0]>>(7-bgpx))&1) | (((pt[1]>>(7-bgpx))&1)<<1) | bgdata.main[bgtile].at;
@ -1890,7 +1898,8 @@ int FCEUX_PPU_Loop(int skip) {
pixelcolor = PALRAM[pixel];
//look for a sprite to be drawn
if(SpriteON)
if(renderspritenow) {
bool havepixel = false;
for(int s=0;s<oamcount;s++) {
uint8* oam = oams[renderslot][s];
int x = oam[3];
@ -1904,6 +1913,9 @@ int FCEUX_PPU_Loop(int skip) {
oam[4] >>= 1;
oam[5] >>= 1;
//bail out if we already have a pixel from a higher priority sprite
if(havepixel) continue;
//transparent pixel bailout
if(spixel==0) continue;
@ -1914,12 +1926,20 @@ int FCEUX_PPU_Loop(int skip) {
if(oam[6] == 0 && pixel != 0)
PPU_status |= 0x40;
havepixel = true;
//priority handling
if(oam[2]&0x20) {
//behind background:
if((pixel&3)!=0) continue;
}
//bring in the palette bits and palettize
spixel |= (oam[2]&3)<<2;
pixelcolor = PALRAM[0x10+spixel];
break;
}
}
}
//fceu rendering system requires that this be set
//(so that it knows there is a valid pixel there?)