Re: help with DHR plotting

[nparker@cie-2.uoregon.edu (Neil Parker)]

In article <Pine.SUN.3.91.951214114944.11011D-100000@owens> Cyrus Roton
<croton@ridgecrest.ca.us> writes:
>On 11 Dec 1995, Neil Parker wrote:
>> In article <Pine.SUN.3.91.951210100139.4708B-100000@owens> Cyrus Roton
>> <croton@ridgecrest.ca.us> writes:
>> >I need help in debugging a double hi-res plotting routine. The following
>> >program steps are used in setting up for DHR plotting:
>> >
>----- snip ------
>> >
>> >The problem is that certain programs (not all of them) which use 80 columns,
>> >seem to leave some softswitch or another set to interfere with this plotting.
>> >The result is thin vertical bands on the plot. I can load and view DHR
>> >properly, I just can't plot properly.
>> >
>> 
>> This differs slightly from the symptoms I've experienced, but I'll risk
>> a guess anyway.
>> 
>> Is your computer by any chance a IIGS?  And are the "certain programs" you
>> mention by any chance Appleworks 2.0?
>---- snip ------
>> 
>>                - Neil Parker
>
>No, I am using a IIe, not a IIgs. I have not tried to see if AW causes 
>the problem. Copy II Plus, Merlin, and the ProDOS "bye" all do cause the 
>symptoms. Sneeze does not.
>
>I had been plotting only every fourth horizontal point since the "brush" 
>is four pixels wide. Usually, that works quite well, until certain 
>programs leave some softswith (or something) in some unexpected 
>condition. The solution I found is to plot all the hoizontal points, 
>rather than only every fourth one. This seems to work quite well, though 
>I still dont know why.
>
>BTW the DHIRES.AMPER program has the same problem, when plotting every 
>fourth point or even every second point, but not when plotting "lines".

Hmm.  This completely blows the shadowing theory away, of course, since
IIe's don't do shadowing.

Actually, it sounds like your DHR plotting routines aren't clearing the
screen properly before they start.  If one of the two screen banks doesn't
get cleared, you may or may not see vertical stripes all over your image,
depending on what state memory was left in by the last program you ran.

See if running this program before your DHR program helps:

     10  HGR : TEXT : REM Clear main bank
     20  POKE 60,0: POKE 61,32: POKE 62,255: POKE 63,63
     30  POKE 66,0: POKE 67,32: REM Set up for AUXMOVE
     40  POKE 6,56: POKE 7,76: POKE 8,17: POKE 9,195
     50  CALL 6: REM Copy main bank to aux bank

If that solves the problem, then you need to take a close look at your
drawing routines, and maybe rewrite the routines that clear the DHR
screen.

               - Neil Parker

P.S  The machine code POKEd in line 40 is
          SEC
          JMP $C311
The entry point at $C311 exists only on the IIe and later machines, and only
if the 80-colunn firmware is switched in.  Running this program under other
circumstances will crash the system.
--
Neil Parker                       | No cute quote, no cute ASCII art, no cute
nparker@cie-2.uoregon.edu         | disclaimer, no deposit, no return....
nparker@cie.uoregon.edu           | (This space intentionally left blank:
http://cie-2.uoregon.edu/~nparker |                                           )