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zero · 13 June 2017, 17:03

Thanks for the great explanation roondar.

I think this shows why hardwaresprites are so great. Any kind of blitter object or CPU soft sprite uses lots of scarce memory bandwidth. Save the background bitmap if needed, read the sprite bitmap, write the sprite bitmap, then next frame restore the background. Masses of copying and register programming.

With hardware sprites you write a few registers and that's it. You loose some memory access cycles for sprite DMA, but only a fraction as many as blitter/soft sprites.

Amiga hardware sprites are quite limited. Games try to make use of them anyway... For example, in Sidewinder the player's bullets are all one sprite, re-used over and over since they can't overlap vertically. A few copper instructions and 68k memory writes instead of multiple blitter operations. I don't know if it even uses sprite DMA... Since the bullets are the same for ever scan line, sprite DMA could be turned off and the buffer registers pre-loaded.

13 June 2017, 17:03	#52
zero Registered User Join Date: Jun 2016 Location: UK Posts: 428	Thanks for the great explanation roondar. I think this shows why hardwaresprites are so great. Any kind of blitter object or CPU soft sprite uses lots of scarce memory bandwidth. Save the background bitmap if needed, read the sprite bitmap, write the sprite bitmap, then next frame restore the background. Masses of copying and register programming. With hardware sprites you write a few registers and that's it. You loose some memory access cycles for sprite DMA, but only a fraction as many as blitter/soft sprites. Amiga hardware sprites are quite limited. Games try to make use of them anyway... For example, in Sidewinder the player's bullets are all one sprite, re-used over and over since they can't overlap vertically. A few copper instructions and 68k memory writes instead of multiple blitter operations. I don't know if it even uses sprite DMA... Since the bullets are the same for ever scan line, sprite DMA could be turned off and the buffer registers pre-loaded.