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Any gotchas reading tile buffer/pattern table?

slobu - Jul 29, 2011

		slobu		Jul 29, 2011
			I've read several VDP docs and I don't see any gotchas. However in my side-scrolling engine I (seem to) have issues with reading tile values at the edges of the buffer. Say the screen is set up as 64x64 tiles I'd have trouble reading values at the 64th column or row. Probably chasing a red herring (or my own sloppy code) but I thought I'd ask if reading tile values from vram can have issues.

		Chilly Willy		Jul 29, 2011
			I'm not aware of any issues with that. Make sure you don't accidentally have a 64 in there somewhere as 64 wide means the index is 0 to 63. If you accidentally tried reading index 64, you'd really get index 0 of the next line.

		slobu		Jul 30, 2011
			Chilly Willy said: I'm not aware of any issues with that. Make sure you don't accidentally have a 64 in there somewhere as 64 wide means the index is 0 to 63. If you accidentally tried reading index 64, you'd really get index 0 of the next line. Thanks for the sanity check! I'm now starting to suspect my own map data loading code. I'm probably triggering the map drawing code over and over again thus borking the tile reading. Being a newbie means rewriting your entire engine over and over again

		Chilly Willy		Jul 30, 2011
			slobu said: Thanks for the sanity check! I'm now starting to suspect my own map data loading code. I'm probably triggering the map drawing code over and over again thus borking the tile reading. Being a newbie means rewriting your entire engine over and over again Yes, I've done that myself any number of times.