mode7.cpp

#ifdef PPU_CPP

//bsnes mode7 renderer
//
//base algorithm written by anomie
//bsnes implementation written by byuu
//
//supports mode 7 + extbg + rotate + zoom + direct color + scrolling + m7sel + windowing + mosaic
//interlace and pseudo-hires support are automatic via main rendering routine

//13-bit sign extend
//--s---vvvvvvvvvv -> ssssssvvvvvvvvvv
#define CLIP(x) ( ((x) & 0x2000) ? ( (x) | ~0x03ff) : ((x) & 0x03ff) )

template<unsigned bg>
void PPU::render_line_mode7(uint8 pri0_pos, uint8 pri1_pos) {
  if(layer_enabled[bg][0] == false) pri0_pos = 0;
  if(layer_enabled[bg][1] == false) pri1_pos = 0;
  if(pri0_pos + pri1_pos == 0) return;

  if(regs.bg_enabled[bg] == false && regs.bgsub_enabled[bg] == false) return;

  int32 px, py;
  int32 tx, ty, tile, palette;

  int32 a = sclip<16>(cache.m7a);
  int32 b = sclip<16>(cache.m7b);
  int32 c = sclip<16>(cache.m7c);
  int32 d = sclip<16>(cache.m7d);

  int32 cx   = sclip<13>(cache.m7x);
  int32 cy   = sclip<13>(cache.m7y);
  int32 hofs = sclip<13>(cache.m7_hofs);
  int32 vofs = sclip<13>(cache.m7_vofs);

  int  _pri, _x;
  bool _bg_enabled    = regs.bg_enabled[bg];
  bool _bgsub_enabled = regs.bgsub_enabled[bg];

  build_window_tables(bg);
  uint8 *wt_main = window[bg].main;
  uint8 *wt_sub  = window[bg].sub;

  int32 y = (regs.mode7_vflip == false ? line : 255 - line);

  uint16 *mtable_x, *mtable_y;
  if(bg == BG1) {
    mtable_x = (uint16*)mosaic_table[(regs.mosaic_enabled[BG1] == true) ? regs.mosaic_size : 0];
    mtable_y = (uint16*)mosaic_table[(regs.mosaic_enabled[BG1] == true) ? regs.mosaic_size : 0];
  } else {  //bg == BG2
    //Mode7 EXTBG BG2 uses BG1 mosaic enable to control vertical mosaic,
    //and BG2 mosaic enable to control horizontal mosaic...
    mtable_x = (uint16*)mosaic_table[(regs.mosaic_enabled[BG2] == true) ? regs.mosaic_size : 0];
    mtable_y = (uint16*)mosaic_table[(regs.mosaic_enabled[BG1] == true) ? regs.mosaic_size : 0];
  }

  int32 psx = ((a * CLIP(hofs - cx)) & ~63) + ((b * CLIP(vofs - cy)) & ~63) + ((b * mtable_y[y]) & ~63) + (cx << 8);
  int32 psy = ((c * CLIP(hofs - cx)) & ~63) + ((d * CLIP(vofs - cy)) & ~63) + ((d * mtable_y[y]) & ~63) + (cy << 8);
  for(int32 x = 0; x < 256; x++) {
    px = psx + (a * mtable_x[x]);
    py = psy + (c * mtable_x[x]);

    //mask floating-point bits (low 8 bits)
    px >>= 8;
    py >>= 8;

    switch(regs.mode7_repeat) {
      case 0:    //screen repetition outside of screen area
      case 1: {  //same as case 0
        px &= 1023;
        py &= 1023;
        tx = ((px >> 3) & 127);
        ty = ((py >> 3) & 127);
        tile    = vram[(ty * 128 + tx) << 1];
        palette = vram[(((tile << 6) + ((py & 7) << 3) + (px & 7)) << 1) + 1];
      } break;
      case 2: {  //palette color 0 outside of screen area
        if((px | py) & ~1023) {
          palette = 0;
        } else {
          px &= 1023;
          py &= 1023;
          tx = ((px >> 3) & 127);
          ty = ((py >> 3) & 127);
          tile    = vram[(ty * 128 + tx) << 1];
          palette = vram[(((tile << 6) + ((py & 7) << 3) + (px & 7)) << 1) + 1];
        }
      } break;
      case 3: {  //character 0 repetition outside of screen area
        if((px | py) & ~1023) {
          tile = 0;
        } else {
          px &= 1023;
          py &= 1023;
          tx = ((px >> 3) & 127);
          ty = ((py >> 3) & 127);
          tile = vram[(ty * 128 + tx) << 1];
        }
        palette = vram[(((tile << 6) + ((py & 7) << 3) + (px & 7)) << 1) + 1];
      } break;
    }

    if(bg == BG1) {
      _pri = pri0_pos;
    } else {
      _pri = (palette >> 7) ? pri1_pos : pri0_pos;
      palette &= 0x7f;
    }

    if(!palette) continue;

    _x = (regs.mode7_hflip == false) ? (x) : (255 - x);

    uint32 col;
    if(regs.direct_color == true && bg == BG1) {
      //direct color mode does not apply to bg2, as it is only 128 colors...
      col = get_direct_color(0, palette);
    } else {
      col = get_palette(palette);
    }

    if(regs.bg_enabled[bg] == true && !wt_main[_x]) {
      if(pixel_cache[_x].pri_main < _pri) {
        pixel_cache[_x].pri_main = _pri;
        pixel_cache[_x].bg_main  = bg;
        pixel_cache[_x].src_main = col;
        pixel_cache[_x].ce_main  = false;
      }
    }
    if(regs.bgsub_enabled[bg] == true && !wt_sub[_x]) {
      if(pixel_cache[_x].pri_sub < _pri) {
        pixel_cache[_x].pri_sub = _pri;
        pixel_cache[_x].bg_sub  = bg;
        pixel_cache[_x].src_sub = col;
        pixel_cache[_x].ce_sub  = false;
      }
    }
  }
}

#undef CLIP

#endif