How to re-position sprites mid-screen?

[Dr. Kylstein]

I want to have multiple rows of enemies that the player must dodge, like the cars from Frogger, except that my player has per-pixel movement. From the look of the horizontal positioning code I've borrowed, it looks like I need (nearly?) a whole line to re-position the second sprite. Is there a trick I'm missing, or do I need to go to two-line? I'm using DPC+.

[Thomas Jentzsch]

You will need at least one scan line for repositioning. But there are some ways to utilize that scan line at least partially. E.g. you can write two (or more) repositioning codes, one for positioning on the left half and one for positioning on the right half. Then you can utilize about half the scan line for other stuff (e.g. drawing the other player).

 

I don't understand why you think you have to go two line.

[Dr. Kylstein]

So if I still knew how to cycle count, it wouldn't be a problem? It's been too long since I've done this stuff.

[+SpiceWare]

I use 11 reposition routines per player (so 22 in all) in Frantic and Space Rocks to reposition the sprites. Those links are to the specific categories in my blog, most of the posts contain the source for that date's version. Later versions of Space Rocks are heavily optimized so it would probably be easier to understand the earlier versions.

 

Both projects include an Open Office spreadsheet that shows the cycle breakdown. I've attached it as a PDF in case you don't have Open Office installed.

 

Cycle position.pdf