mirror of https://github.com/bsnes-emu/bsnes.git
108 lines
2.7 KiB
C++
108 lines
2.7 KiB
C++
#ifdef PPU_CPP
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signed PPU::Background::clip(signed n) {
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//13-bit sign extend: --s---nnnnnnnnnn -> ssssssnnnnnnnnnn
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return n & 0x2000 ? (n | ~1023) : (n & 1023);
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}
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//H = 28
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void PPU::Background::begin_mode7() {
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cache.hoffset = self.regs.mode7_hoffset;
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cache.voffset = self.regs.mode7_voffset;
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}
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void PPU::Background::run_mode7() {
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signed a = sclip<16>(self.regs.m7a);
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signed b = sclip<16>(self.regs.m7b);
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signed c = sclip<16>(self.regs.m7c);
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signed d = sclip<16>(self.regs.m7d);
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signed cx = sclip<13>(self.regs.m7x);
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signed cy = sclip<13>(self.regs.m7y);
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signed hoffset = sclip<13>(cache.hoffset);
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signed voffset = sclip<13>(cache.voffset);
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if(Background::x++ & ~255) return;
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unsigned x = mosaic.hoffset;
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unsigned y = self.bg1.mosaic.voffset; //BG2 vertical mosaic uses BG1 mosaic size
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if(--mosaic.hcounter == 0) {
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mosaic.hcounter = regs.mosaic + 1;
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mosaic.hoffset += regs.mosaic + 1;
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}
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if(self.regs.mode7_hflip) x = 255 - x;
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if(self.regs.mode7_vflip) y = 255 - y;
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signed psx = ((a * clip(hoffset - cx)) & ~63) + ((b * clip(voffset - cy)) & ~63) + ((b * y) & ~63) + (cx << 8);
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signed psy = ((c * clip(hoffset - cx)) & ~63) + ((d * clip(voffset - cy)) & ~63) + ((d * y) & ~63) + (cy << 8);
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signed px = psx + (a * x);
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signed py = psy + (c * x);
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//mask pseudo-FP bits
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px >>= 8;
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py >>= 8;
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unsigned tile;
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unsigned palette;
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switch(self.regs.mode7_repeat) {
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//screen repetition outside of screen area
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case 0:
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case 1:
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px &= 1023;
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py &= 1023;
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tile = ppu.vram[((py >> 3) * 128 + (px >> 3)) << 1];
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palette = ppu.vram[(((tile << 6) + ((py & 7) << 3) + (px & 7)) << 1) + 1];
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break;
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//palette color 0 outside of screen area
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case 2:
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if((px | py) & ~1023) {
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palette = 0;
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} else {
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px &= 1023;
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py &= 1023;
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tile = ppu.vram[((py >> 3) * 128 + (px >> 3)) << 1];
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palette = ppu.vram[(((tile << 6) + ((py & 7) << 3) + (px & 7)) << 1) + 1];
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}
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break;
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//character 0 repetition outside of screen area
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case 3:
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if((px | py) & ~1023) {
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tile = 0;
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} else {
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px &= 1023;
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py &= 1023;
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tile = ppu.vram[((py >> 3) * 128 + (px >> 3)) << 1];
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}
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palette = ppu.vram[(((tile << 6) + ((py & 7) << 3) + (px & 7)) << 1) + 1];
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break;
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}
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unsigned priority;
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if(id == ID::BG1) {
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priority = regs.priority0;
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} else if(id == ID::BG2) {
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priority = (palette & 0x80 ? regs.priority1 : regs.priority0);
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palette &= 0x7f;
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}
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if(palette == 0) return;
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if(regs.main_enable) {
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output.main.palette = palette;
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output.main.priority = priority;
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output.main.tile = 0;
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}
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if(regs.sub_enable) {
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output.sub.palette = palette;
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output.sub.priority = priority;
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output.sub.tile = 0;
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}
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}
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#endif
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