[Coco] [Color Computer] Chet Simpson's Sprite Compiler

[Robert Gault]

James Diffendaffer wrote:
><snip>
> interleaved being...
> 
> copy bytes left to right on row 1
> copy bytes right to left on row 2
> copy bytes left to right on row 3
> etc...
> 
> This was commonly used on the Speccy for large sprites so that less
> manipulation of the pointer was required.  And yes, sprite data was
> stored in reverse order on even rows.
> 
> 
> 

Well on a Coco, going from one screen line to the next will always 
require adding to the pointer register the width of the screen to get to 
the byte on the next line. If you are really pressed for speed, it might 
make sense to just add the screen width and alternate right and left. 
That would remove the need for repeatedly calculating the width plus 
screen offset and only require it once at the beginning of the routine. 
It would trade off somewhat faster code for more code to handle the 
right/left alternation.

You would certainly need to count cycles to see of there was a net gain 
or loss in speed.