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

[John Kowalski]

At 10:59 PM 07/02/2007 -0000, James Diffendaffer wrote:

>I don't know if it would even be required on the 6809 but did this
>tool also deal with larger sprites and interleave the drawing of the
>sprite.
>
>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.

The 6809 could do it either way without advantage or penalty.  The index
pointer can be auto incremented or decremented.  The only possible advantage
may be if doing it one way results in an 8-bit addition to get to the next
line rather than requiring a 16-bit addition.


The best speed improvement would most likely actually be to draw the bytes
out of order entirely.  Preload color/byte values which are repeated
multiple times in the sprite images and write each of them in all their
locations before moving onto the next color/byte values.   This reduces
loading operations (multiple stores per load instead of 1:1).

                                         John Kowalski (Sock Master)
                                         http://www.axess.com/twilight/sock/