|
|
Atari coding BBS
| Re: clear pixel |
|---|
|
Posted by: evil
|
Oct,24.2013-16:58
|
Well it's a way to optimize away the code modifying for the clearing with CPU and the clear-list alltogether with the blitter.
CPU-example:
Say you have a list of
or.b dn,ofs(a0)
or.b dn,ofs(a0)
or.b dn,ofs(a0)
or.b dn,ofs(a0)
etc
For plotting pixels, the calc-routine routine will selfmodify the codelist and write screen offsets (to ofs) and datareg (instruction word, dn) into the list. That's for plotting, not that uncommon I guess.
Then for clearing, you'd normally need something similar;
clr.b ofs(a0)
clr.b ofs(a0)
clr.b ofs(a0)
clr.b ofs(a0)
etc
The calc-rout would have to write the offset into the clearing code as well.
Glokys clever idea is to reuse the "ofs" part of the instruction from the plotcode. Eliminating the need to selfmodify two code-lists, so his clear will look like (a0=the plotcode list):
move.l (a0)+,d0 ;fetch the plot instruction and offset
clr.b (a1,d0.w) ;use the low word of d0 for clear offset
It's smart stuff, I like it :)
Blitter-example:
His second idea about using the blitter to change the opcode in the plotcode-list and save the offset. Very smart as well as the blitter will do auto increment and you can move the opcode from Halftone blitter memory, 4 cycles per replaced instruction.
Eg, before the blitterpass the plotcode-list looks like before:
or.b dn,ofs(a0)
or.b dn,ofs(a0)
etc
After the blitterpass it will look like:
clr.b ofs(a0)
clr.b ofs(a0)
etc
The calc-code will restore the opcode from clr.b to or.b the next frame.
Salutations to gloky for clever coding :)
--
Anders Eriksson
ae@dhs.nu
|
[All messages in this thread] [Start new thread]
|
Topic
|
Posted by
|
Date
|
|
clear pixel
|
gloky
|
Oct,20.2013-11:44
|
|
Re: clear pixel
|
specter
|
Oct,24.2013-04:19
|
|
Re: clear pixel
|
evil
|
Oct,24.2013-16:58
|
|
Re: clear pixel
|
nerve
|
Oct,25.2013-18:18
|
|
Re: clear pixel
|
gwEm
|
Oct,27.2013-22:57
|
|
Re: clear pixel
|
gloky
|
Nov,05.2013-09:29
|
|
Re: clear pixel
|
Leonard
|
Nov,13.2013-02:30
|
|
Re: clear pixel
|
gloky
|
Nov,16.2013-12:54
|
|
Re: clear pixel
|
gloky
|
Nov,27.2013-00:44
|
|
Re: clear pixel
|
RA/pdx
|
Nov,13.2013-10:27
|
|
Re: clear pixel
|
leonard
|
Nov,14.2013-01:15
|
|
Re: clear pixel
|
RA/pdx
|
Nov,14.2013-10:01
|
|
Re: clear pixel
|
leonard
|
Nov,16.2013-11:49
|
What's the anti-troll code?
That's your personal code to be able to add comments and messages on the dhs.nu site.
Don't have a code or forgot it? Fix it here.
|
