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Old 26 January 2012, 14:51   #31
Mrs Beanbag
Glastonbridge Software
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Join Date: Jan 2012
Location: Edinburgh/Scotland
Posts: 2,202
With AGA a 1:1 conversion is almost possible, but not quite. Maybe you could get a 99:100 conversion! I'm working on this myself...

Sonic's background graphics is 16 colours, foreground is also 16 colours, sprites however use a different palette and the amiga is limited to four 16 colour sprites, or three if you want to do full-screen scrolling (because setting DDFSTRT early interferes with the sprite DMA so you lose sprite 7 - but you can still use sprite 6 in 3 colours only).

AGA can handle 64 pixel wide sprites however, so Sonic only needs to take up one of them (that is one 16 colour sprite), and it could be possible to multiplex them (the same sprite can be reused in several places on the screen if you are cunning) but objects that are too common, such as rings, will have to be drawn directly to the background. Note also that on Sonic some static background objects are actually sprites as well (for instance the purple rocks). Also the HUD at top left would also need to be made out of (3 colour) sprites.

50fps is easily achievable with all the parallax graphics exactly the same as Sonic, the only degradation you might have to put up with is a reduction in colours to allow some things to be drawn as bobs.

AGA could do it no problem, it has enough grunt to push 6 bitplanes without any copper tricks ... and can chuck around more bobs.
I'm not aware of AGA having a faster blitter than ECS - do correct me if I'm wrong. What is true though is that with 32 bit or 64 bit graphics DMA fetching there is more chip ram bandwidth available to it.
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