cannot get playfield to work

[Rudy]

I can set color but the playfield flickers and isn't vertically aligned properly and I can't figure out how to fix it even though i read the manual. Any help appreciated.

[+Random Terrain]

If you attach your .bas file, we can look at it.

[Rudy]

It's on another computer but I'll try to get it with a thumb drive. Just a minute.

 

rem test maze game aug 4 2014
rem set smartbranching on
COLUBK = $0E
COLUPF = $00

playfield:
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
end

drawscreen
end

Edited August 5, 2014 by Rudy

[SeaGtGruff]

Well, it's okay to define the playfield just once like that, but you need to put the drawscreen in a loop so the 2600 keeps drawing it 60-ish times a second. So just change the last part of your program to something like

 

 

loop
   drawscreen
   goto loop
end

[Rudy]

I tried to upload the .bas file but I couldn't get the button to work (when I clicked, nothing happened).

[Rudy]

Here I got it.

test2.bas

[+Random Terrain]

SeaGtGruff already posted what is wrong, but here it is in a .bas file:

 

rudy_test_2014y_08m_04d_2349t.bas

 

 

There are a bunch of example program links on the right side of the bB page that might be helpful:

 

randomterrain.com/atari-2600-memories-batari-basic-commands.html#example_programs

[Rudy]

Thank you.

[+Gemintronic]

The drawscreen command tells the 2600 to draw the sprites, playfield, ball and missiles. After everything is drawn you can determine whether a collision happened or not. Another tricky thing is that some graphical attributes get wiped after a drawscreen. For instance, if your player0 was bright pink (NTSC) you must set COLUP0 = $4E again!

[bogax]

Just to elaborate a little bit

The television wants a frame every
1/60 of a second and displays the
picture/frame a line at a time going
from left to right, top to bottom
The processor (roughly speaking) creates
the picture in realtime a line at a time
as it's displayed.

When it's done drawing the screen there's
little bit of time left over before the
processor needs to start drawing the next
frame.

That's when your program runs.

So you call drawscreen and the processor
waits for the starting time of the next
frame and then draws the screen and when it's
done drawing the screen it returns from
drawscreen and goes on with your code.

So normally you run a loop to call drawscreen
(approximately) periodically, before the start
of the next frame but it doesn't actually have
be a (simple) loop or a loop with just one drawscreen.
you just have to make sure you call drawscreen
before the next frame should start.

So for example you could make a program that
was just a long list of drawscreens with out
looping and it would display a picture until
you ran out of drawscreens. (say 600 drawscreens/
2k * 1/60 of second/drawscreen = about 10 seconds
so with 2k you could display for 10 seconds
before you ran out but you wouldn't be able to do
anything else)

[Rudy]

Thanks again for all the help. I'll let you know what progress I make.

[SeaGtGruff]

Thanks again for all the help. I'll let you know what progress I make.

 

We're looking forward to seeing what you make!

[Rudy]

I won't be working on this again until monday but I'll report then on my progress.