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zero · 12 October 2017, 17:14

I count six words moved per scanline for three sprites. No sprite bitmap DMA at all.

So in total you need 6 moves for the sprites, 2 for the road fill and two or three to change the palette. That's 11 per scanline.

Compared to blitting which needs you to wait for the blitter to complete, re-load address registers, calculate shift values and load them, then write the control registers. And do the colour palette changes, the same as my scheme. And on multiple bitplanes if you want grass/road/road markings.

In the best case you need 2 bitplanes, assuming you use dual-playfield to avoid having to share bitplanes with objects. And for the next frame you have to clear at least part of what you previously copied if you have hills.

Oh, and while the blitter is running the CPU is losing memory access slots to DMA, and the blitter isn't available to draw objects.

12 October 2017, 17:14	#301
zero Registered User Join Date: Jun 2016 Location: UK Posts: 428	I count six words moved per scanline for three sprites. No sprite bitmap DMA at all. So in total you need 6 moves for the sprites, 2 for the road fill and two or three to change the palette. That's 11 per scanline. Compared to blitting which needs you to wait for the blitter to complete, re-load address registers, calculate shift values and load them, then write the control registers. And do the colour palette changes, the same as my scheme. And on multiple bitplanes if you want grass/road/road markings. In the best case you need 2 bitplanes, assuming you use dual-playfield to avoid having to share bitplanes with objects. And for the next frame you have to clear at least part of what you previously copied if you have hills. Oh, and while the blitter is running the CPU is losing memory access slots to DMA, and the blitter isn't available to draw objects. Last edited by zero; 13 October 2017 at 13:20.