Path: blob/master/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/PPU.run.cs
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//http://nesdev.parodius.com/bbs/viewtopic.php?p=4571&sid=db4c7e35316cc5d734606dd02f11dccb
//todo - read http://wiki.nesdev.com/w/index.php/PPU_sprite_priority
//TODO - correctly emulate PPU OFF state
using BizHawk.Common;
using System;
namespace BizHawk.Emulation.Cores.Nintendo.NES
{
sealed partial class PPU
{
const int kFetchTime = 2;
struct BGDataRecord
{
public byte nt, at;
public byte pt_0, pt_1;
};
public short[] xbuf = new short[256 * 240];
// values here are used in sprite evaluation
public bool sprite_eval_write;
public byte read_value;
public int soam_index;
public int soam_index_prev;
public int soam_m_index;
public int oam_index;
public int read_value_aux;
public int soam_m_index_aux;
public int oam_index_aux;
public bool is_even_cycle;
public bool sprite_zero_in_range = false;
public bool sprite_zero_go = false;
public int yp;
public int target;
public int spriteHeight;
public byte[] soam = new byte[512]; // in a real nes, this would only be 32, but we wish to allow more then 8 sprites per scanline
public bool reg_2001_color_disable_latch; // the value used here is taken
public bool conflict_2006, ppu_was_on;
struct TempOAM
{
public byte oam_y;
public byte oam_ind;
public byte oam_attr;
public byte oam_x;
public byte patterns_0;
public byte patterns_1;
}
TempOAM[] t_oam = new TempOAM[64];
int ppu_addr_temp;
void Read_bgdata(ref BGDataRecord bgdata)
{
for (int i = 0; i < 8; i++)
Read_bgdata(i, ref bgdata);
}
// attempt to emulate graphics pipeline behaviour
// experimental
int pixelcolor_latch_1;
int pixelcolor_latch_2;
void pipeline(int pixelcolor, int target, int row_check)
{
if (row_check > 1)
{
if (reg_2001.color_disable)
pixelcolor_latch_2 &= 0x30;
xbuf[(target - 2)] = PaletteAdjustPixel(pixelcolor_latch_2);
}
if (row_check >= 1)
{
pixelcolor_latch_2 = pixelcolor_latch_1;
}
pixelcolor_latch_1 = pixelcolor;
}
void Read_bgdata(int cycle, ref BGDataRecord bgdata)
{
switch (cycle)
{
case 0:
ppu_addr_temp = ppur.get_ntread();
bgdata.nt = ppubus_read(ppu_addr_temp, true, true);
runppu(1);
break;
case 1:
runppu(1);
break;
case 2:
{
ppu_addr_temp = ppur.get_atread();
byte at = ppubus_read(ppu_addr_temp, true, true);
//modify at to get appropriate palette shift
if ((ppur.vt & 2) != 0) at >>= 4;
if ((ppur.ht & 2) != 0) at >>= 2;
at &= 0x03;
at <<= 2;
bgdata.at = at;
runppu(1);
break;
}
case 3:
runppu(1);
break;
case 4:
ppu_addr_temp = ppur.get_ptread(bgdata.nt);
bgdata.pt_0 = ppubus_read(ppu_addr_temp, true, true);
runppu(1);
break;
case 5:
runppu(1);
break;
case 6:
ppu_addr_temp |= 8;
bgdata.pt_1 = ppubus_read(ppu_addr_temp, true, true);
runppu(1);
if (reg_2001.PPUON)
{
ppu_was_on = true;
}
break;
case 7:
runppu(1);
//horizontal scroll clocked at cycle 3 and then
//vertical scroll at 256
if (ppu_was_on)
{
ppur.increment_hsc();
if (ppur.status.cycle == 256 && !conflict_2006)
ppur.increment_vs();
}
ppu_was_on = false;
break;
} //switch(cycle)
}
//TODO - check flashing sirens in werewolf
short PaletteAdjustPixel(int pixel)
{
//tack on the deemph bits. THESE MAY BE ORDERED WRONG. PLEASE CHECK IN THE PALETTE CODE
return (short)(pixel | reg_2001.intensity_lsl_6);
}
const int kLineTime = 341;
public unsafe void FrameAdvance()
{
BGDataRecord* bgdata = stackalloc BGDataRecord[34]; //one at the end is junk, it can never be rendered
//262 scanlines
if (ppudead != 0)
{
FrameAdvance_ppudead();
return;
}
Reg2002_vblank_active_pending = true;
ppuphase = PPUPHASE.VBL;
ppur.status.sl = 241;
//Not sure if this is correct. According to Matt Conte and my own tests, it is. Timing is probably off, though.
//NOTE: Not having this here breaks a Super Donkey Kong game.
if (reg_2001.show_obj || reg_2001.show_bg) reg_2003 = 0;
//this was repeatedly finetuned from the fceux days thrugh the old cpu core and into the new one to pass 05-nmi_timing.nes
//note that there is still some leniency. for instance, 4,2 will pass in addition to 3,3
const int delay = 6;
runppu(3);
bool nmi_destiny = reg_2000.vblank_nmi_gen && Reg2002_vblank_active;
runppu(3);
if (nmi_destiny) TriggerNMI();
nes.Board.AtVsyncNMI();
runppu(postNMIlines * kLineTime - delay);
//this seems to run just before the dummy scanline begins
clear_2002();
idleSynch ^= true;
//render 241 scanlines (including 1 dummy at beginning)
for (int sl = 0; sl < 241; sl++)
{
ppur.status.cycle = 0;
ppur.status.sl = sl;
soam_index = 0;
soam_m_index = 0;
soam_m_index_aux = 0;
oam_index_aux = 0;
oam_index = 0;
is_even_cycle = true;
sprite_eval_write = true;
sprite_zero_go = false;
if (sprite_zero_in_range)
sprite_zero_go = true;
sprite_zero_in_range = false;
yp = sl - 1;
ppuphase = PPUPHASE.BG;
if (NTViewCallback != null && yp == NTViewCallback.Scanline) NTViewCallback.Callback();
if (PPUViewCallback != null && yp == PPUViewCallback.Scanline) PPUViewCallback.Callback();
//ok, we're also going to draw here.
//unless we're on the first dummy scanline
if (sl != 0)
{
//the main scanline rendering loop:
//32 times, we will fetch a tile and then render 8 pixels.
//two of those tiles were read in the last scanline.
int yp_shift = yp << 8;
for (int xt = 0; xt < 32; xt++)
{
int xstart = xt << 3;
target = yp_shift + xstart;
int rasterpos = xstart;
spriteHeight = reg_2000.obj_size_16 ? 16 : 8;
//check all the conditions that can cause things to render in these 8px
bool renderspritenow = reg_2001.show_obj && (xt > 0 || reg_2001.show_obj_leftmost);
bool renderbgnow;
for (int xp = 0; xp < 8; xp++, rasterpos++)
{
//////////////////////////////////////////////////
//Sprite Evaluation Start
//////////////////////////////////////////////////
if (ppur.status.cycle <= 63 && !is_even_cycle)
{
// the first 64 cycles of each scanline are used to initialize sceondary OAM
// the actual effect setting a flag that always returns 0xFF from a OAM read
// this is a bit of a shortcut to save some instructions
// data is read from OAM as normal but never used
soam[soam_index] = 0xFF;
soam_index++;
}
if (ppur.status.cycle == 64)
soam_index = 0;
// otherwise, scan through OAM and test if sprites are in range
// if they are, they get copied to the secondary OAM
if (ppur.status.cycle >= 64)
{
if (oam_index == 64)
{
sprite_eval_write = false;
}
if (is_even_cycle && oam_index<64)
{
read_value = OAM[oam_index * 4 + soam_m_index];
if (oam_index_aux > 63)
oam_index_aux = 63;
read_value_aux = OAM[oam_index_aux * 4 + soam_m_index_aux];
}
else if (sprite_eval_write)
{
if (soam_index >= 8)
{
// this code mirrors sprite overflow bug behaviour
// see http://wiki.nesdev.com/w/index.php/PPU_sprite_evaluation
if (yp >= read_value && yp < read_value + spriteHeight && reg_2001.PPUON)
{
Reg2002_objoverflow = true;
}
else
{
soam_m_index++;
oam_index++;
if (soam_m_index == 4)
soam_m_index = 0;
}
}
//look for sprites
soam[soam_index * 4] = OAM[oam_index_aux * 4];
if (yp >= read_value_aux && yp < read_value_aux + spriteHeight && soam_m_index_aux == 0)
{
//a flag gets set if sprite zero is in range
if (oam_index_aux == 0)
sprite_zero_in_range = true;
soam_m_index_aux++;
}
else if (soam_m_index_aux > 0 && soam_m_index_aux < 4)
{
soam[soam_index * 4 + soam_m_index_aux] = OAM[oam_index_aux * 4 + soam_m_index_aux];
soam_m_index_aux++;
if (soam_m_index_aux == 4)
{
oam_index_aux++;
soam_index++;
soam_m_index_aux = 0;
}
}
else
{
oam_index_aux++;
}
if (soam_index < 8)
{
soam_m_index = soam_m_index_aux;
oam_index = oam_index_aux;
}
}
}
//////////////////////////////////////////////////
//Sprite Evaluation End
//////////////////////////////////////////////////
//process the current clock's worth of bg data fetching
//this needs to be split into 8 pieces or else exact sprite 0 hitting wont work due to the cpu not running while the sprite renders below
if (reg_2001.show_obj || reg_2001.show_bg)
Read_bgdata(xp, ref bgdata[xt + 2]);
else
runppu(1);
renderbgnow = reg_2001.show_bg && (xt > 0 || reg_2001.show_bg_leftmost);
//bg pos is different from raster pos due to its offsetability.
//so adjust for that here
int bgpos = rasterpos + ppur.fh;
int bgpx = bgpos & 7;
int bgtile = bgpos >> 3;
int pixel = 0, pixelcolor = PALRAM[pixel];
//according to qeed's doc, use palette 0 or $2006's value if it is & 0x3Fxx
//at one point I commented this out to fix bottom-left garbage in DW4. but it's needed for full_nes_palette.
//solution is to only run when PPU is actually OFF (left-suppression doesnt count)
if (!reg_2001.show_bg && !reg_2001.show_obj)
{
// if there's anything wrong with how we're doing this, someone please chime in
int addr = ppur.get_2007access();
if ((addr & 0x3F00) == 0x3F00)
{
pixel = addr & 0x1F;
}
pixelcolor = PALRAM[pixel];
pixelcolor |= 0x8000; //whats this? i think its a flag to indicate a hidden background to be used by the canvas filling logic later
}
//generate the BG data
if (renderbgnow)
{
byte pt_0 = bgdata[bgtile].pt_0;
byte pt_1 = bgdata[bgtile].pt_1;
int sel = 7 - bgpx;
pixel = ((pt_0 >> sel) & 1) | (((pt_1 >> sel) & 1) << 1);
if (pixel != 0)
pixel |= bgdata[bgtile].at;
pixelcolor = PALRAM[pixel];
}
if (!nes.Settings.DispBackground)
pixelcolor = 0x8000; //whats this? i think its a flag to indicate a hidden background to be used by the canvas filling logic later
//look for a sprite to be drawn
bool havepixel = false;
for (int s = 0; s < soam_index_prev; s++)
{
int x = t_oam[s].oam_x;
if (rasterpos >= x && rasterpos < x + 8)
{
//build the pixel.
//fetch the LSB of the patterns
int spixel = t_oam[s].patterns_0 & 1;
spixel |= (t_oam[s].patterns_1 & 1) << 1;
//shift down the patterns so the next pixel is in the LSB
t_oam[s].patterns_0 >>= 1;
t_oam[s].patterns_1 >>= 1;
//bail out if we already have a pixel from a higher priority sprite.
//notice that we continue looping anyway, so that we can shift down the patterns
//transparent pixel bailout
if (!renderspritenow || havepixel || spixel == 0) continue;
havepixel = true;
//TODO - make sure we dont trigger spritehit if the edges are masked for either BG or OBJ
//spritehit:
//1. is it sprite#0?
//2. is the bg pixel nonzero?
//then, it is spritehit.
Reg2002_objhit |= (sprite_zero_go && s == 0 && pixel != 0 && rasterpos < 255 && reg_2001.show_bg && reg_2001.show_obj);
//priority handling, if in front of BG:
bool drawsprite = !(((t_oam[s].oam_attr & 0x20) != 0) && ((pixel & 3) != 0));
if (drawsprite && nes.Settings.DispSprites)
{
//bring in the palette bits and palettize
spixel |= (t_oam[s].oam_attr & 3) << 2;
//save it for use in the framebuffer
pixelcolor = PALRAM[0x10 + spixel];
}
} //rasterpos in sprite range
} //oamcount loop
/*
if (reg_2001.color_disable)
pixelcolor &= 0x30;
xbuf[target] = PaletteAdjustPixel(pixelcolor);
*/
pipeline(pixelcolor, target, xt*32+xp);
target++;
} //loop across 8 pixels
} //loop across 32 tiles
}
else
for (int xt = 0; xt < 32; xt++)
Read_bgdata(ref bgdata[xt + 2]);
// normally only 8 sprites are allowed, but with a particular setting we can have more then that
// this extra bit is here because the actual loop doesn't have enough time to scann all sprites if there are more then 8
if (nes.Settings.AllowMoreThanEightSprites)
{
while (oam_index_aux < 64)
{
//look for sprites
soam[soam_index * 4] = OAM[oam_index_aux * 4];
read_value_aux = OAM[oam_index_aux * 4];
if (yp >= read_value_aux && yp < read_value_aux + spriteHeight)
{
soam[soam_index * 4 + 1] = OAM[oam_index_aux * 4 + 1];
soam[soam_index * 4 + 2] = OAM[oam_index_aux * 4 + 2];
soam[soam_index * 4 + 3] = OAM[oam_index_aux * 4 + 3];
soam_index++;
oam_index_aux++;
}
else
{
oam_index_aux++;
}
}
}
soam_index_prev = soam_index;
if (soam_index_prev > 8 && !nes.Settings.AllowMoreThanEightSprites)
soam_index_prev = 8;
ppuphase = PPUPHASE.OBJ;
spriteHeight = reg_2000.obj_size_16 ? 16 : 8;
// if there are less then 8 evaluated sprites, we still process 8 sprites
int bound;
if (soam_index_prev > 8)
{
bound = soam_index_prev;
}
else
{
bound = 8;
}
for (int s = 0; s < 8; s++)
{
//if this is a real sprite sprite, then it is not above the 8 sprite limit.
//this is how we support the no 8 sprite limit feature.
//not that at some point we may need a virtual CALL_PPUREAD which just peeks and doesnt increment any counters
//this could be handy for the debugging tools also
bool realSprite = (s < 8);
bool junksprite = (!reg_2001.PPUON);
t_oam[s].oam_y = soam[s * 4];
t_oam[s].oam_ind = soam[s * 4 + 1];
t_oam[s].oam_attr = soam[s * 4 + 2];
t_oam[s].oam_x = soam[s * 4 + 3];
int line = yp - t_oam[s].oam_y;
if ((t_oam[s].oam_attr & 0x80) != 0) //vflip
line = spriteHeight - line - 1;
int patternNumber = t_oam[s].oam_ind;
int patternAddress;
//8x16 sprite handling:
if (reg_2000.obj_size_16)
{
int bank = (patternNumber & 1) << 12;
patternNumber = patternNumber & ~1;
patternNumber |= (line >> 3) & 1;
patternAddress = (patternNumber << 4) | bank;
}
else
patternAddress = (patternNumber << 4) | (reg_2000.obj_pattern_hi << 12);
//offset into the pattern for the current line.
//tricky: tall sprites have already had lines>8 taken care of by getting a new pattern number above.
//so we just need the line offset for the second pattern
patternAddress += line & 7;
//garbage nametable fetches + scroll resets
int garbage_todo = 2;
ppubus_read(ppur.get_ntread(), true, true);
if (reg_2001.PPUON)
{
if (sl == 0 && ppur.status.cycle == 304)
{
runppu(1);
read_value = t_oam[s].oam_y;
if (reg_2001.PPUON) ppur.install_latches();
runppu(1);
read_value = t_oam[s].oam_ind;
garbage_todo = 0;
}
if ((sl != 0) && ppur.status.cycle == 256)
{
runppu(1);
if (target<=61441 && target > 0 && s==0)
{
pipeline(0, target,256);
target++;
}
read_value = t_oam[s].oam_y;
//at 257: 3d world runner is ugly if we do this at 256
if (reg_2001.PPUON) ppur.install_h_latches();
runppu(1);
if (target <= 61441 && target > 0 && s==0)
{
pipeline(0, target, 257); // last pipeline call option 1 of 2
}
read_value = t_oam[s].oam_ind;
garbage_todo = 0;
}
}
if (realSprite)
{
for (int i = 0; i < garbage_todo; i++)
{
runppu(1);
if (i == 0)
{
if (target <= 61441 && target > 0 && s==0)
{
pipeline(0, target,256);
target++;
}
read_value = t_oam[s].oam_y;
}
else
{
if (target <= 61441 && target > 0 && s==0)
{
pipeline(0, target, 257); // last pipeline call option 2 of 2
}
read_value = t_oam[s].oam_ind;
}
}
}
ppubus_read(ppur.get_atread(), true, true); //at or nt?
if (realSprite)
{
runppu(1);
read_value = t_oam[s].oam_attr;
runppu(1);
read_value = t_oam[s].oam_x;
}
// TODO - fake sprites should not come through ppubus_read but rather peek it
// (at least, they should not probe it with AddressPPU. maybe the difference between peek and read is not necessary)
if (junksprite)
{
if (realSprite)
{
ppubus_read(patternAddress, true, false);
ppubus_read(patternAddress, true, false);
runppu(kFetchTime * 2);
}
}
else
{
int addr = patternAddress;
t_oam[s].patterns_0 = ppubus_read(addr, true, true);
if (realSprite)
{
runppu(kFetchTime);
read_value = t_oam[s].oam_x;
}
addr += 8;
t_oam[s].patterns_1 = ppubus_read(addr, true, true);
if (realSprite)
{
runppu(kFetchTime);
read_value = t_oam[s].oam_x;
}
// hflip
if ((t_oam[s].oam_attr & 0x40) == 0)
{
t_oam[s].patterns_0 = BitReverse.Byte8[t_oam[s].patterns_0];
t_oam[s].patterns_1 = BitReverse.Byte8[t_oam[s].patterns_1];
}
}
} // sprite pattern fetch loop
//now do the same for extra sprites, but without any cycles run
if (bound>8)
{
for (int s = 8; s < bound; s++)
{
bool junksprite = (!reg_2001.PPUON);
t_oam[s].oam_y = soam[s * 4];
t_oam[s].oam_ind = soam[s * 4 + 1];
t_oam[s].oam_attr = soam[s * 4 + 2];
t_oam[s].oam_x = soam[s * 4 + 3];
int line = yp - t_oam[s].oam_y;
if ((t_oam[s].oam_attr & 0x80) != 0) //vflip
line = spriteHeight - line - 1;
int patternNumber = t_oam[s].oam_ind;
int patternAddress;
//8x16 sprite handling:
if (reg_2000.obj_size_16)
{
int bank = (patternNumber & 1) << 12;
patternNumber = patternNumber & ~1;
patternNumber |= (line >> 3) & 1;
patternAddress = (patternNumber << 4) | bank;
}
else
patternAddress = (patternNumber << 4) | (reg_2000.obj_pattern_hi << 12);
//offset into the pattern for the current line.
//tricky: tall sprites have already had lines>8 taken care of by getting a new pattern number above.
//so we just need the line offset for the second pattern
patternAddress += line & 7;
//garbage nametable fetches + scroll resets
int garbage_todo = 2;
ppubus_read(ppur.get_ntread(), true, false);
for (int i = 0; i < garbage_todo; i++)
{
if (i == 0)
{
read_value = t_oam[s].oam_y;
}
else
{
read_value = t_oam[s].oam_ind;
}
}
ppubus_read(ppur.get_atread(), true, false); //at or nt?
read_value = t_oam[s].oam_attr;
read_value = t_oam[s].oam_x;
int addr = patternAddress;
t_oam[s].patterns_0 = ppubus_read(addr, true, false);
read_value = t_oam[s].oam_x;
addr += 8;
t_oam[s].patterns_1 = ppubus_read(addr, true, false);
read_value = t_oam[s].oam_x;
// hflip
if ((t_oam[s].oam_attr & 0x40) == 0)
{
t_oam[s].patterns_0 = BitReverse.Byte8[t_oam[s].patterns_0];
t_oam[s].patterns_1 = BitReverse.Byte8[t_oam[s].patterns_1];
}
} // sprite pattern fetch loop
}
ppuphase = PPUPHASE.BG;
// fetch BG: two tiles for next line
for (int xt = 0; xt < 2; xt++)
{
Read_bgdata(ref bgdata[xt]);
}
// this sequence is tuned to pass 10-even_odd_timing.nes
runppu(kFetchTime);
bool evenOddDestiny = (reg_2001.show_bg || reg_2001.show_obj);
runppu(kFetchTime);
// After memory access 170, the PPU simply rests for 4 cycles (or the
// equivelant of half a memory access cycle) before repeating the whole
// pixel/scanline rendering process. If the scanline being rendered is the very
// first one on every second frame, then this delay simply doesn't exist.
if (sl == 0 && idleSynch && evenOddDestiny && chopdot)
{ }
else
runppu(1);
conflict_2006 = false;
} // scanline loop
ppur.status.sl = 241;
//idle for pre NMI lines
runppu(preNMIlines * kLineTime);
} //FrameAdvance
void FrameAdvance_ppudead()
{
//not quite emulating all the NES power up behavior
//since it is known that the NES ignores writes to some
//register before around a full frame, but no games
//should write to those regs during that time, it needs
//to wait for vblank
/*
if (ppudead < 2)
{
ppur.status.sl = 241;
runppu(1);
Reg2002_vblank_active = true;
runppu(5);
runppu(postNMIlines * kLineTime - 6);
ppur.status.sl = 0;
clear_2002();
}
if (ppudead==2)
{
*/
runppu(241 * kLineTime-7*3);
/*
} else
{
runppu(241 * kLineTime);
runppu(preNMIlines * kLineTime);
idleSynch ^= true;
}
*/
ppudead--;
}
}
}