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PostPosted: Sun May 21, 2017 4:47 pm 
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Bitbeam wrote:
You can temporarily stretch your image from 256 pixels wide to 298 pixels wide to preview how your art will look once its showing on an actual SNES.

The PAR for NTSC is 8:7, which is 292.57/256, not 298/256. Stretching to 293 is probably close enough; I'm sure it varied a bit between TVs.

The PAR for PAL is roughly 11:8, which is 352/256 or more accurately 354.86/256. This means that art drawn for an NTSC SNES will look fat on a PAL SNES.

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however you can opt to use a 16x16 tile mode instead, which would allow for level maps being twice as high and wide in pixels

It's not quite that simple. Level maps are usually far larger than tilemaps. You use map scrolling techniques (using DMA to overwrite rows and/or columns in a tilemap between frames) to seamlessly move around the level map. Since a lot of developers use metatiles in their level formats, using 16x16 tiles might not even save any ROM, though it could save some CPU time when generating the tilemap data from the level data.

The most obvious advantage is that it saves a bit of VRAM, since you only need one map to do horizontal scrolling. You could also use the same map to handle more than one layer, if you were careful with scroll values; with HDMA to handle mid-screen scroll changes you could even do vertical scrolling of both layers. This sort of thing can add up fast - horizontal scrolling with three layers of 8x8 tiles takes six tilemaps, or 12 KB, which is a significant chunk of the 64 KB VRAM, but with 16x16 tiles it could be done in about 3 KB if you're clever (you can store tiles in the tilemap area if you know that part of the tilemap isn't going to be onscreen) or 6 KB with no cleverness whatsoever.

Basically it covers more real estate for the same amount of VRAM.

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Each layer can use up to 1,024 tiles, limited by the amount of VRAM being used by all other graphical assets.

Your next statement, regarding tile flipping, notes that Mode 7 is the exception to it. It's true in this case too. Mode 7 can only use 256 tiles.

It's a severe limitation, especially with the lack of flipping. You actually can't do a fullscreen full-resolution image in Mode 7 without repeating tiles, because 256 tiles is only a 128x128 square. Mind you, you can still fill the screen because of the scaling capability afforded by the transform matrix, and if you do reuse tiles the map is an immense 1024x1024 texels; it's just that if you convert an arbitrary image to Mode 7, and it doesn't happen to have repeating patterns that align to an 8x8 grid, it will have to be either blocky or small.


Last edited by 93143 on Sun May 21, 2017 7:55 pm, edited 1 time in total.

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PostPosted: Sun May 21, 2017 5:26 pm 
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Joined: Mon Jan 23, 2006 7:47 am
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93143 wrote:
not 298/256

My fault, wrote 298 above before noticing and fixing it.


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