Please help consolidate Megadrive info for pixel artists
Posted: Tue May 30, 2017 1:26 pm
Hi everyone. I'm a long time pro pixel artist (and also Genesis/Megadrive fan) and I'm working on rounding up concise and clear (artist friendly) info to help pixel artist who want to make authentic moc-ups and game art for the Megadrive. (I'm also doing this for all the other popular classic consoles.)
I want to create as clear and concise a document as possible (for artists) where every sentence offers definitive guidance for exactly what rules and limits to follow, without drowning, confusing or intimidating artists with lots of technical jargon.
The final document will eventually be a web page, with attached images, animations, examples, and links to communities like this, and also special thanks to anyone who helped improve or confirm or clarify any of the information. This information will also be distributed with the industry standard pixel art program, so It's my hope this will encourage and entice many of today's best pixel artists to fall in love with developing art and games for the Megadrive.
Here's (below) what I have so far. Can anyone who's interested please suggest edits, additions and provide the critical missing info?
One thing I know I really need to add is proper instructions for that special darken and brighten mode the Megadrive had which could darken parts of the screen or brighten. Does anyone know how we artists should approach using/representing this feature? Firstly, what is the exact math used by the Megadrive to do the darkening and the brightening. Secondly, does this work over both background layers and sprites at the same time? Thirdly, can artists paint directly using those darkened and lightened versions of the colors, or only create monochrome overlays to effect the underlying graphics, similar to having layers in Photoshop set to screen and multiply mode?
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Sega Megadrive/Genesis
Graphical summary
Standard game resolution: 320x224 or 256x224
color range: The Megadrive uses 3 bits per color channel, providing a palette of 512 colors.
Number of color indexes available: Typically 64 indexes used, broken into four 16 color palettes. The first color index of each 16 color palette is always used for transparent/
Background graphics color limitations:
The Megadrive allows for 2 scrolling layers, 1 sprite layer, and one non scrolling “window” layer typically used for the games HUD (life bars, score etc.). Each scrolling layer is made of 8x8 pixel tiles. Each tile can be 16 colors, using one of any of the 4 available 16 color palettes.
Unlike 8 bit consoles, there is not a fixed number of unique tiles that can be used, as you can store tile images in any part of available vram.
The number of background tiles can range from 64 to 1808 tiles
Background tiles CAN be flipped horizontally or vertically OR BOTH at the same time!
On top of the 2 separate background layers, either of them can be individually sliced horizontally in order to add even more parts of the background scrolling at separate speeds to create the illusion or dept in scrolling games.
Sprites
Sprites: The Megadrive can display 20 fifteen color (plus a “clear” index for transparent pixels) sprites per scan line (row of pixels on screen).
Each sprite can use any of the four 16 color palettes, with the first color index of each 16 color palette being used for transparent pixels.
80 sprites on screen in total, but any more than 20 per scan line will result in some sprites not being displayed.
Each sprite can be set to any combination of the following dimensions for either width and height separately: 8,16,24 and 32 pixels, resulting in 16 different possible sprite sizes. Each sprite can be set to its own dimensions (from these options) regardless of the size settings for the other sprites. Making the sprites larger than 8x8 does not reduce the possible number of on-screen sprites or number of sprites per scan line BUT once 320 pixels of sprite data are drawn per scan line, no more sprites will be drawn on that scan line.
Up to 1280 tiles can be dedicated to sprites, separate from the background tiles.
Sprites can be horizontally or vertically flipped or both at the same time!
For more detailed technical references:
http://md.squee.co/VDP
https://emudocs.org/Genesis/Graphics/genvdp.txt
http://www.genny4ever.net/index.php?page=docs
http://segaretro.org/Sega_Mega_Drive
___________________________________________________________________________________________________________________________________________________________________
Thanks so much for your time, any help would be greatly appreciated.
I want to create as clear and concise a document as possible (for artists) where every sentence offers definitive guidance for exactly what rules and limits to follow, without drowning, confusing or intimidating artists with lots of technical jargon.
The final document will eventually be a web page, with attached images, animations, examples, and links to communities like this, and also special thanks to anyone who helped improve or confirm or clarify any of the information. This information will also be distributed with the industry standard pixel art program, so It's my hope this will encourage and entice many of today's best pixel artists to fall in love with developing art and games for the Megadrive.
Here's (below) what I have so far. Can anyone who's interested please suggest edits, additions and provide the critical missing info?
One thing I know I really need to add is proper instructions for that special darken and brighten mode the Megadrive had which could darken parts of the screen or brighten. Does anyone know how we artists should approach using/representing this feature? Firstly, what is the exact math used by the Megadrive to do the darkening and the brightening. Secondly, does this work over both background layers and sprites at the same time? Thirdly, can artists paint directly using those darkened and lightened versions of the colors, or only create monochrome overlays to effect the underlying graphics, similar to having layers in Photoshop set to screen and multiply mode?
_____________________________________________________________________________________________________________________________________________________________________
Sega Megadrive/Genesis
Graphical summary
Standard game resolution: 320x224 or 256x224
color range: The Megadrive uses 3 bits per color channel, providing a palette of 512 colors.
Number of color indexes available: Typically 64 indexes used, broken into four 16 color palettes. The first color index of each 16 color palette is always used for transparent/
Background graphics color limitations:
The Megadrive allows for 2 scrolling layers, 1 sprite layer, and one non scrolling “window” layer typically used for the games HUD (life bars, score etc.). Each scrolling layer is made of 8x8 pixel tiles. Each tile can be 16 colors, using one of any of the 4 available 16 color palettes.
Unlike 8 bit consoles, there is not a fixed number of unique tiles that can be used, as you can store tile images in any part of available vram.
The number of background tiles can range from 64 to 1808 tiles
Background tiles CAN be flipped horizontally or vertically OR BOTH at the same time!
On top of the 2 separate background layers, either of them can be individually sliced horizontally in order to add even more parts of the background scrolling at separate speeds to create the illusion or dept in scrolling games.
Sprites
Sprites: The Megadrive can display 20 fifteen color (plus a “clear” index for transparent pixels) sprites per scan line (row of pixels on screen).
Each sprite can use any of the four 16 color palettes, with the first color index of each 16 color palette being used for transparent pixels.
80 sprites on screen in total, but any more than 20 per scan line will result in some sprites not being displayed.
Each sprite can be set to any combination of the following dimensions for either width and height separately: 8,16,24 and 32 pixels, resulting in 16 different possible sprite sizes. Each sprite can be set to its own dimensions (from these options) regardless of the size settings for the other sprites. Making the sprites larger than 8x8 does not reduce the possible number of on-screen sprites or number of sprites per scan line BUT once 320 pixels of sprite data are drawn per scan line, no more sprites will be drawn on that scan line.
Up to 1280 tiles can be dedicated to sprites, separate from the background tiles.
Sprites can be horizontally or vertically flipped or both at the same time!
For more detailed technical references:
http://md.squee.co/VDP
https://emudocs.org/Genesis/Graphics/genvdp.txt
http://www.genny4ever.net/index.php?page=docs
http://segaretro.org/Sega_Mega_Drive
___________________________________________________________________________________________________________________________________________________________________
Thanks so much for your time, any help would be greatly appreciated.