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atari800 moving dot across screen


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Here it is.. had to put into Altirra emulator as copy and paste works well there. There is a little less flicker with altirra but still has a little.



10 GRAPHICS 3+16
20 FOR X=0 TO 39
30 COLOR 65
40 PLOT X,10
50 FOR T=1 TO 50:NEXT T
60 COLOR 0
70 PLOT X,10
90 GOTO 20
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Since Basic is slow it'll flicker.


Can be made more bearable - stack statements on lines for a bit of speedup. Put the once used stuff before the loop in a subroutine around 1000 to speed up loops.


For your program there, remove lines 60, 70.

Then change:



30 COLOR 0 : PLOT XP,YP : COLOR 1 : PLOT X,10 : XP=X : YP = 10


Gr. 3 only has 4 colours (0-3) so no point trying for color 65.

Edited by Rybags
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10 GRAPHICS 3+16
20 FOR Z=0 TO 39:PLOT X,10:COLOR 1:PLOT Z,10:X=Z
40 GOTO 20




10 GRAPHICS 3+16
30 GOTO 20

Edited by _The Doctor__
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Just tried the original code and The doctors optimized code on real Atari with CRT...


The original code has a very barely slight additional flicker compared to the optimized code, but really only because I'm looking for it haha. Interesting to see the optimization of the code.

Edited by Nezgar
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now just for fun play with values of T. It can be used to show some tricks depending on monitor and especially lcd tv's....

pick a value of...

7 looks good? now 3.... hey what happened?

15 looks good? now nudge it up or down a number at a time.. the block scoots forward or slides back, intensity may change to your eye

31 etc etc..


This happens because the picture is black during the drawing of our object... the monitor is out of sync with our source... on a real CRT it will be synchronized and drawn as the beam arrives then it persists due to phosphorescence and our own eyes


on an LCD if it's not there during processing, it drops it.... so by varying the delay you change the relationship, the plotted point will blink out of existence, appear to jump forward or slide possibly jerk back... even what you perceive as surging or lagging....on a CRT you can kind of get the same results but it's not as easy to do...


I really dislike modern displays for so many reasons


in order to do justice to any real video, a VGA should refresh at 72 hz that's 3x the cinema 24 rate..... that so much material already exist at 'movies experience'


that same rate is why flat panels say motion rate 240... it's 10 time the rate of 24..... why so high.... because anything less can be terrible on an all on all off screen or gets missed during decoding.... even if they output it at some crappy 60 or 120 output rate, it samples it that many time and includes all the changes in the frame that it sends to the lcd matrix... covering up the miss match a little... that's why I look for a true lcd panel rate not the motion rating or such other rating...

Edited by _The Doctor__
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