You have to load the second tile of the line before rendering starts. That means tilemap and tile data for up to 4 BGs must be present for 2 complete tiles before you start.

you can load 2 bytes per dot, and you render one pixel or 2 half-pixels in high res in that time.

worst case, you have to reload everything after 1 pixel. The SNES can't do that, but 8 pixels is just enough to do that, necessitating caching a second tile. (1 dot = 1 16-bit read, so 1 tilemap or 1 2bpp chunk of 8 pixels). This is why every time you raise the bit depth, the layers drop: to shift bandwidth to accomodate more planes being fetched.

Work it out, you NEED 2 tiles to draw at all with 7 pixels of the first tile scrolled off the left edge of the screen. Can't work any other way (although the order BGs are fetched in isn't assured, and it's unknown how tiles and tilemaps are interleaved)

This only affects a given line. The whole proces restarts on the next line.

Last edited by Heretical_One; 08/17/09 01:35 AM.