10-08-2018, 06:58 AM
Hi Domarius,
Sorry for the late reply to your interesting question.
In classic systems, the tileset (the graphics) and the tilemap must fit inside the VRAM. The VRAM provided space to hold a portion of the tilemap that wast a bit bigger that the screen, so you could scroll a small window inside it.Scrolling the whole map required a combination of moving the window inside the viewport, that wrapped around the edges, and "streaming" new tileset data from the ROM to the VRAM. I recommend you to check an emulator with graphical debugging capabilities (like the Gens KMod or Meka). These emulators can show the VRAM area of the viewport updating the tilemap in realtime as the game progresses.
Tilengine is different in this regard. The whole tileset and tilemap are loaded into RAM, so you can locate the viewport at any section without having to stream tiles from another place. Of course the original behavior can be emulated in tilengine too, using a small tilemap layer that works as the viewport and then copy sections of the tilemap, but it would be really cumbersome.
Sorry for the late reply to your interesting question.
In classic systems, the tileset (the graphics) and the tilemap must fit inside the VRAM. The VRAM provided space to hold a portion of the tilemap that wast a bit bigger that the screen, so you could scroll a small window inside it.Scrolling the whole map required a combination of moving the window inside the viewport, that wrapped around the edges, and "streaming" new tileset data from the ROM to the VRAM. I recommend you to check an emulator with graphical debugging capabilities (like the Gens KMod or Meka). These emulators can show the VRAM area of the viewport updating the tilemap in realtime as the game progresses.
Tilengine is different in this regard. The whole tileset and tilemap are loaded into RAM, so you can locate the viewport at any section without having to stream tiles from another place. Of course the original behavior can be emulated in tilengine too, using a small tilemap layer that works as the viewport and then copy sections of the tilemap, but it would be really cumbersome.