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GBA dev and tile sizes

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I am looking into developing a 2d side-scroller GBA game as a hobby project and let me say up front that I am an graphic artist and not a coder. For now I am looking into the feasibility of my idea. What I''d like to know, and hopefully somebody can answer this, is what the possibilities are for the background scrolling side of the game. I know that a way to create the scrolling background layer(s) is to create 1 image file that contains small square tile images that u use to construct your background with. What I didn''t find in the tutorials I''ve found online is what the biggest tile size can be. And is "tiles" the only way to create a scrolling background landscape? Can''t you just use a long image of a landscape that is repeated endless?

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for GBA h/w you can create display images in two different ways. Tiles and pixels. Using the bitmap modes (3,4,5) you can have more colors but at a smaller resolution. Tile modes (0,1,2) are setup so you place your tiles into VRAM and it will display and scroll them as necassary (to a degree). Programming for the GBA is not something to be attempted by non-coders. Not trying to stop you, just saying look for a partner in crime.

the visual specs go something like this:

mode 0, Tiles, 4 layers, 256 or 16x16 colors, 1024 sprites, layers are 256x256 or 512x512 (depending on colors used(i think))

mode 1, Tiles, 1 layers, 256 colors, 256 sprites, layers are 128x128 to 1024x1024

mode 2, Tiles, 2 layers, 256 colors, 256 sprites, layers are 128x128 to 1024x1024

mode 3, Bitmap, 32768 colors, 1 frame, 240x160

mode 4, Bitmap, 256 colros, 2 frames, 240x160

mode 5, Bitmap, 32768 colors, 2 frames 160x128

Some of these choices may not seem worthwhile but that's because there are other factors that are involved in the mode selection (h/w sprite rotation, alpha transparency, h/w luminosity, h/w mosaic effects).

Edited by - Jim_Ross on January 8, 2002 5:22:10 PM

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Thanks for your clear reply!
I am not planning on doing any coding myself but am collecting specs for the graphics which is my area so that I know some of the possibilities and limitations that I need to write the graphics part of the design document.

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Guest Anonymous Poster
I beleive the tile size for the GBA background is a 8x8. Sprite sizes can be different sizes.. from 8x8 to 64x64 i beleive. If you write your background scrolling functions yourself, you can use 8x8<->64x64.. if you use the built in (hardware) functions, I beleive you''re stuck with 8x8 tiles (which isn''t a bad thing).

Billy - BillyB@mrsnj.com

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All the tiles in what i call 'tile mode' are 8x8, as anonymous said. The sprites are a slightly different story. GBA supports "objects" of 8x8 -> 64x64 sizes, but that is not a limiting factor of sprites. A sprite can be constructed of 4 "objects". Think of dracula in circle of the moon (CotM). He took up approx. half the screen (240x160) so i dare say he was bigger than 64x64. He was probably made of 4 32x32 objects arranged in a grid (just a guess).

If you're writing a design doc, keep this in mind. Most gameplay/level bgs are done in tile modes (0-2), most intro/cutscene/option menus are done in bitmap modes (3-5). Look at CotM when you die. The screen says game over, then falls away like grains of sand. Most likely that was done in a bitmap mode and the programmer had some pixel -> sand function. I'm pretty sure you can have objects in both bg modes, but i've never tried sprites on a bitmap bg. My guess is that a game like broken sword (http://gamespot.com/gamespot/stories/previews/0,10869,2774009,00.html) uses bitmap bgs w/characters as objects. You could easily write a tool to define areas on a nice image that are 'walkable' and define how much to scale a character at certain positions - to simulate depth. Don't forget that in most modes any sprite can be rotated, flipped, scaled, transparent using GBA h/w (easy on the programmer).

Edited by - Jim_Ross on January 10, 2002 10:56:42 AM

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