Is there a way to turn the playfield on and off while remembering its previous state?

[Words Fail]

Scenario: I draw a playfield at the start of a level, you fly over some of that play field causing it to disappear.

 

Is there a way I can turn the playfield off and then back on while remembering its previous state of which blocks you made disappear already?

 

 

[+Gemintronic]

In the standard kernel you can access the playfield as variables using var0-47.  So, you can copy chunks of the playfield and save them for later. 

https://www.randomterrain.com/atari-2600-memories-batari-basic-commands.html#standardmemorymap

 

Problem is: you only have 26 normal variables to play with and the playfield itself is made up of more variables than that.

 

You could reduce the playfield to 6 rows and use the left over vars as a backup copy of the playfield.  A little chunky looking but doable.

 

https://www.randomterrain.com/atari-2600-memories-batari-basic-commands.html#pfres

[Words Fail]

2 hours ago, Gemintronic said:

In the standard kernel you can access the playfield as variables using var0-47.  So, you can copy chunks of the playfield and save them for later. 

https://www.randomterrain.com/atari-2600-memories-batari-basic-commands.html#standardmemorymap

 

Problem is: you only have 26 normal variables to play with and the playfield itself is made up of more variables than that.

 

You could reduce the playfield to 6 rows and use the left over vars as a backup copy of the playfield.  A little chunky looking but doable.

 

https://www.randomterrain.com/atari-2600-memories-batari-basic-commands.html#pfres

I think I'll just skip this all together, although I am going to be switching to DPC+ shortly if that makes a difference.

 

Here's the idea.. there's a Pac-Man bootleg called Piranha where you move a fish around. On some of the levels the dots or level disappears (I can't remember) disappear. I was going to have my blocks show for 3 seconds, disappear for 3, show for 3, etc. You can only get them when they're on.

[+Random Terrain]

Maybe I'm not reading your question correctly, but if you want everything to disappear, can't you make the foreground the color of the background? Then restore the color when you want it to appear again?

[KevKelley]

2 hours ago, Random Terrain said:

Maybe I'm not reading your question correctly, but if you want everything to disappear, can't you make the foreground the color of the background? Then restore the color when you want it to appear again?

And building on this idea couldn’t you have the collision detection and deletion be conditional on the color value of the playfield?

[+Al_Nafuur]

14 hours ago, Words Fail said:

Scenario: I draw a playfield at the start of a level, you fly over some of that play field causing it to disappear.

 

Is there a way I can turn the playfield off and then back on while remembering its previous state of which blocks you made disappear already?

 

 

To toggle a single playfield pixel you can use pfpixel with the flip parameter. If you flip it even times it will have the same state as before your blinking, with odd time it will have the opposite value. This is not recommendable for a large amount of playfield pixel, because it needs 80 CPU cycles.

 

You can invert a whole byte (8 pixel) with the ASM command "eor" and the original bytes value. e.g.:

	asm
	lda var20		; your playfield byte in RAM
	eor %10101010		; invert with original bitmask on accumulator
	sta var20		; store back to RAM
end

This will only cost you 8 CPU cycles per byte

 

If you want to blink the whole playfield the color trick described by @Random Terrain and @KevKelley is the best way to do it.

 

[KevKelley]

6 hours ago, Al_Nafuur said:

 

You can invert a whole byte (8 pixel) with the ASM co

This is awesome. I love seeing the ASM equivalents of things as they help me learn and of course the trade off with saving cycles

[Words Fail]

On 12/21/2022 at 6:43 PM, Random Terrain said:

Maybe I'm not reading your question correctly, but if you want everything to disappear, can't you make the foreground the color of the background? Then restore the color when you want it to appear again?

You're right! I can't believe I didn't think of that.

[Words Fail]

21 hours ago, KevKelley said:

And building on this idea couldn’t you have the collision detection and deletion be conditional on the color value of the playfield?

Yes, now that you say it. I already have my collision detection working though.. it just looks if the pixel is on or not.

[+Random Terrain]

39 minutes ago, Words Fail said:

Yes, now that you say it. I already have my collision detection working though.. it just looks if the pixel is on or not.

 

You could have a bit turned on when collision detection is active and turn it off when it's not. If the bit is off, skip the collision detection section.

[Words Fail]

24 minutes ago, Random Terrain said:

 

You could have a bit turned on when collision detection is active and turn it off when it's not. If the bit is off, skip the collision detection section.

 

Collision detection is always on. My program looks what x and y coordinate you are at.

 

coldet
 if player0x=21 then d = 1: f = 2: goto coldet2
 if player0x=23 then d = 1: f = 2: goto coldet2
 if player0x=33 then d = 4: f = 5: goto coldet2
 if player0x=45 then d = 7: f = 8: goto coldet2
 if player0x=57 then d = 10: f = 11: goto coldet2
 if player0x=69 then d = 13: f = 14: goto coldet2
 if player0x=81 then d = 16: f = 17: goto coldet2
 if player0x=93 then d = 19: f = 20: goto coldet2
 if player0x=105 then d = 22: f = 23: goto coldet2
 if player0x=117 then d = 25: f = 26: goto coldet2
 if player0x=127 then d = 28: f = 29: goto coldet2
 if player0x=129 then d = 28: f = 29: goto coldet2
 return

coldet2
 if player0y=18 then e = 3: goto coldet3
 if player0y=26 then e = 5: goto coldet3
 if player0y=34 then e = 7: goto coldet3
 if player0y=42 then e = 9: goto coldet3
 if player0y=50 then e = 11: goto coldet3
 if player0y=58 then e = 13: goto coldet3
 if player0y=66 then e = 15: goto coldet3
 if player0y=74 then e = 17: goto coldet3
 if player0y=82 then e = 19: goto coldet3
 return

coldet3
 if pfread(d,e) then pfhline d e f off: c=c-1: score = score + 50
 if c=0 then goto levelend
 return

 

It first checks your x pos. If it is one of those it is setting variables to tell the program which two pixels I need to turn off. Each block is made up of two blocks actually. So in this case player0x is 33 for example it's going to set variable d to 4 which is your x pos.

 

If not one of those positions it returns. If it is then it checks your y pos.. if not one of those listed it returns.. if so then and sets variable e.

 

If then checks if the coordinate is on or off. If it's on then it turns it off, takes variable c down, and gives you score. Once c is 0 means all blocks are gone and do level end stuff.

 

A lot of that will probably change because I have to convert my game over to DPC+.. I'll ask about that elsewhere.

 

 

[+Random Terrain]

If you want no collision when the foreground can't be seen, here's an example:

 

   if !_Bit0_Collision{0} then goto __Skip_Collision_Check

   ; Your collision code goes here

__Skip_Collision_Check

 

 

The _Bit0_Collision{0} bit would be on when the foreground can be seen and turned off when the foreground can't be seen.