Shooting Sprite (Screw Up?)

[KevKelley]

I was working on a little program and made a section with two sprites that can shoot in seven directions.  I had initially gotten the code working for P0.  I pretty much copied it for P1 but I couldn't get it working right and I don't know what I screwed up but I've been staring at the screen and my brain is dead.

 

Here is the P0 code that works:

 if g{1} || f{1} then goto SKIP_FIRE
 if !joy0fire then goto SKIP_FIRE

 if joy0left then f{0}=1
 if joy0up  then f{2}=1
 if joy0down then f{3}=1

 if joy0up && joy0right then g{2}=1:f{0}=1
 if joy0down && joy0right then g{2}=1:f{0}=1
 if joy0up && !joy0left then g{3}=1:f{0}=1
 if joy0down && !joy0left then g{3}=1:f{0}=1

 if f{0} then missile0x=player0x+3:missile0y=player0y-4:f{1}=1 
SKIP_FIRE
 if g{2} then missile0x=missile0x+4
 if g{3} then missile0x=missile0x+2

 if f{1} then missile0x=missile0x-2:f{0}=0
 if f{2} then missile0y=missile0y-1:if g{3} then missile0y=missile0y-1
 if f{3} then missile0y=missile0y+1:if g{3} then missile0y=missile0y+1
 if collision(missile0,playfield) then f{0}=0:f{1}=0:f{2}=0:f{3}=0:g{2}=0:g{3}=0
 if !f{1} then missile0y=200

SKIP_SHOOTING_0

Here is the P1 code:

 if g{0} ||  f{5}  then goto SKIP_FIRE2
 if !joy1fire then goto SKIP_FIRE2 


 if joy1right then f{4}=1
 if  joy1up  then f{6}=1
 if joy1down then f{7}=1

 if joy1up && joy1left then g{4}=1:f{4}=1
 if joy1down && joy1left then g{4}=1:f{4}=1
 if joy1up && !joy1right then g{5}=1:f{4}=1
 if joy1down && !joy1right then g{5}=1:f{4}=1


 if f{4} then missile1x=player1x+5:missile1y=player1y-4:f{5}=1 
SKIP_FIRE2
 if g{4} then missile1x=missile1x-4
 if g{5} then missile1x=missile1x-2

 if f{5} then missile1x=missile1x+2:f{4}=0
 if f{6} then missile1y=missile1y-1:if g{5} then missile1y=missile1y-1
 if f{7} then missile1y=missile1y+1:if g{5} then missile1y=missile1y+1
 if collision(missile1,playfield) then f{4}=0:f{5}=0:f{6}=0:f{7}=0:g{4}=0:g{5}=0
 if !f{5} then missile1y=200

It seems to only work firing UP, DOWN, RIGHT, UP LEFT

 

It does not go UP RIGHT, DOWN RIGHT, or DOWN LEFT.

 

 

Now I did notice that when I deleted this line for the P1 code it kind of worked (except that you wouldn't have to hit the fire button.)

 

 if !joy1fire then goto SKIP_FIRE2 

Here is the bB file too.  Am I blind?

CB_12_11_2020.bas

Edited December 12, 2020 by KevKelley
Added detail.

[+Random Terrain]

I sent someone a PM about something in your code. When they get back to me, I'll get back to you. May not even have anything to do with the problem you're having.

[KevKelley]

9 minutes ago, Random Terrain said:

I sent someone a PM about something in your code. When they get back to me, I'll get back to you. May not even have anything to do with the problem you're having.

Thanks. It was driving me crazy. It kept throwing me off thinking it was something that related to either the fire or one of the directionals I made or some weird interaction with some of the other code in the program but I would comment sections out to see if it changed and nothing was different. I also was wondering if something was getting lost in the operations but the P0 was throwing me off.yp

 

And I did notice after testing that I would get an occasional shot here or there and every once and a while the shot would freeze.

 

I was hoping to pick it back up tonight and see if I can find the issue. 

[KevKelley]

I was looking over the code and was wondering...

 

Is it possible that because of how I have it written, with there being multiple checks (if joy1up then..., if joy1up && joyleft then...) and because I have the part with the !joy1fire, that the game happens to take my first entry, and then goes with it, essentially locking out some of the other options? If that is the case, the only thing I don't get is why it would work for P) and not P1.

[+Random Terrain]

Have you looked at this program on the bB page:

 

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

[KevKelley]

19 minutes ago, Random Terrain said:

Have you looked at this program on the bB page:

 

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

I had not.  I was looking at some of the other programs though in developing this. Originally I had a simpler shooting but then kept expanding on it to be multi-directional.  Looking at that program that is a hell of a lot simpler then what my brain was putting together.  That would probably make things easier down the road, too.

[bogax]

My suggestion is to read Advanced Joystick Reading with SWCHA

 

then abandon that mess of if-then spaghetti

 

and do your missile move with look up tables (instead of on gosub/goto as in the examples)

[KevKelley]

2 hours ago, bogax said:

My suggestion is to read Advanced Joystick Reading with SWCHA

 

then abandon that mess of if-then spaghetti

 

and do your missile move with look up tables (instead of on gosub/goto as in the examples)

I had played around with SWCHA before.  I am definitely going to look at that.  Some of it confused me when I had first tried to implement it in some programs before.

 

Funny.  I would sometimes start with a simple program and then just playing around with things I tend to over complicate stuff. Sometimes I don't think about it much because I figure it is something small and I don't need the space.  With this I thought I'd just cut and paste some of my code and go from there.

[KevKelley]

Quote

Instead of using a long list of if…then statements, an on…gosub or on…goto statement can be used. For Joy0, we read the value in SWCHA and divide it by 16 which discards the Joy1 bits and shifts the joy0 bits into the lower 4 bit positons, so we'd use temp1 = SWCHA / 16. For Joy1, temp1 = SWCHA & %00001111 would be used.

 

-from Random Terrain's website

 

So, if I were to use it, I would essentially set 2 temp variables for each controller and then do something like this:

 

on temp2=%01000000 goto... 

on temp1=%00001100 goto...

 

with it going to which ever directional issue?

[KevKelley]

So I was playing around with SWCHA and I think I understand it much better then a year ago when I first started messing around with it (also with on...goto statements).

 

You are right.  Instead of cooked spaghetti my code looks like uncooked spaghetti!

 temp1  =  SWCHA / 16

   on temp1 goto P0_STILL P0_STILL P0_STILL P0_STILL P0_STILL P0_GO_DR P0_GO_UR P0_GO_R P0_STILL P0_GO_DL  P0_GO_UL P0_GO_L P0_STILL P0_GO_D P0_GO_U P0_STILL

DONE_JOY0

 

I have the various movements off in a different section where I have the speed at which they move.  I guess I can then also add in those sections the direction for the missile direction.  It will probably get me a little to get comfortable with it and play around but this is definitely much cleaner and looks like it will help in the longrun!  

 

Thanks!

 

 

[bogax]

this is something like what I had in mind  (untested)

    dim pj0f = temp1
    dim  m0d = m                             ;  missile 0 direction

    pj0f = j0f                               ;  remember if joy0fire was pressed before
    if joy0fire then j0f = 1 else j0f = 0    ;  remember if joy0fire is pressed now
    if !pj0f then skip_m0_direction          ;  skip setting the m0 direction if joy0fire wasn't pressed before
    if j0f then skip_m0_direction            ;  joy0fire was pressed before skip setting the m0 direction if it's still pressed

    ;  set missile 0 direction
    m0d = (SWCHA ^ %11111111) / 16           ;  joy0 bits are rlduxxxx of SWCHA
                                             ;  if a direction is active the bit is 0 eg right-up is 0110xxxx
                                             ;  ^ with 1 will flip a 1 bit to 0 and a 0 bit to 1 so right-up will be 1001xxxx
                                             ;  then divide by 16 to get 0000rldu so right up will be 00001001

skip_m0_direction

    if !m0d then skip_move_m0                ;  if m0d is 0 then the missile is parked off screen don't move it

    ;  move missile 0

    missile0x = missile0x + m0x[m0d]
    missile0y = missile0y + m0y[m0d]

skip_move_m0


  ; 0    1    2    3    4    5    6    7    8    9   10
  ;      u    d   du    l   lu   ld   ldu   r   ru   rd

    data m0x
    0,   0,   0,   0,   0,  -1,  -1,   0,   1,   1,   1
end

    data m0y
    0,  -1,   1,   0,   0,  -1,   1,   0,   0,  -1,   1
end

  the value in the table is the speed

Edited December 13, 2020 by bogax

[KevKelley]

Ah. 
 

I was just playing around with the example program to see what I could do with that. 

I haven't really used data tables too much but I like it. I guess I had not gotten to the point where I kind of understand some of these things but to determine what purpose they serve sometimes eludes me.

 

I was curious.  In the example you posted above, what is the j0f?  I did not see it defined.

27 minutes ago, bogax said:

pj0f = j0f

 

[bogax]

6 minutes ago, KevKelley said:

 

I was curious.  In the example you posted above, what is the j0f?  I did not see it defined.

 

oops

a flag to remember the state of joy0fire

the code is written as if its a full variable, but it only needs a single bit 

Edited December 12, 2020 by bogax

[KevKelley]

Okay.  

 

So if I were to also make something like this for Missile1, I would use something like this for Joy1 inputs:

 

m1d= SWCHA^%11111111

 

And I can use the same data tables as m0d?

 

and thank you so much!  This is very helpful! 

[bogax]

  yes except you need to mask out the joy0 bits of SWCHA

  m1d= SWCHA ^ %11111111 & %00001111
  

Edited December 12, 2020 by bogax

[KevKelley]

Thank you @bogax!

 

So I was playing around with the code inside my original program to get it to work and after some tweaking here and there I fit it in!  

 

I had made a couple adjustments to get it to work.  Here is what I did:

    if collision(ball,player0) then goto skip_m0_direction
    if j0f{0} then  missile0x=player0x+3:missile0y=player0y-4
                     
    pj0f = j0f                               
    if joy0fire then j0f{0} = 1 else j0f{0} = 0    
    if !pj0f then skip_m0_direction          
    if j0f then skip_m0_direction           
    
    m0d = (SWCHA ^ %11111111) / 16           

skip_m0_direction
    if !m0d then missile0x=200:missile0y=200: goto skip_move_m0               

    missile0x = missile0x + m0x[m]
    missile0y = missile0y + m0y[m]

skip_move_m0
 if collision(missile0,playfield) then m0d=0

    data m0x
    0,   0,   0,   0,   -1,  -1,  -1,   0,   1,   1,   1
end

    data m0y
    0,  -1,   1,   0,   0,  -1,   1,   0,   0,  -1,   1
end

 

I had added the check so that it spawns the missile by the player. 

I had added the coordinates to put the missile off screen.

I deleted the 0 in the data table bracket.

I changed a value in the table to allow for shooting in all directions (originally I was going to not shoot backwards  but this method made it much easier).

I also added where if you grab the ball in the game the shot continues but it is still locked out.

 

This has been a very good lesson for me, as I had always been confused by some concepts, like SWCHA or data tables. I had only previously used a data table for the lightning sound in Bag Boy when I tried using data tables for sound for some reason (I kept it because I liked the effect even though it didn't end up how I expected). And looking at my old code for the SWCHA, I don't know what I was thinking.  I think I just inserted the defining of the temp value but then never did anything with it. 

 

Now all I gotta do is copy this for Player1 and delete my old code and check any other code that previously used the spaghetti code.  

 

Thank you @Random Terrain too!  Your site and sample programs have again proven to be invaluable! I truly wish one day it could be in a book form so I can bring it with me everywhere!

Edited December 13, 2020 by KevKelley

[KevKelley]

I just replaced the shooting code in my program with the new shooting code and I noticed that the same issue with the P1 shooting exists, where it does not shoot in certain directions (UR, DR, and DL).

 

By chance I played the file in z26 and it seemed that all directions seems to work.  I tried again in Stella 6.0.2 and it didn't work.

 

Weird.

CB_12_12_2020_A.bas

Edited December 13, 2020 by KevKelley

[bogax]

2 hours ago, KevKelley said:

I just replaced the shooting code in my program with the new shooting code and I noticed that the same issue with the P1 shooting exists, where it does not shoot in certain directions (UR, DR, and DL).

 

By chance I played the file in z26 and it seemed that all directions seems to work.  I tried again in Stella 6.0.2 and it didn't work.

 

Weird.

CB_12_12_2020_A.bas 10.75 kB · 2 downloads

I'm not sure what to make of it

 

I suspect it may be a keyboard-instead-of-joystick problem

 

 

I noticed a couple other things

 

You're doing something with bit 1 of f so you should use a different bit for the fire button flag

If you're going to use a single bit you have to use a single bit in the if statments too

You should move the initialization of the missile position to where missile direction gets set

Edited December 13, 2020 by bogax

[KevKelley]

12 hours ago, bogax said:

You're doing something with bit 1 of f so you should use a different bit for the fire button flag

If you're going to use a single bit you have to use a single bit in the if statments too

You should move the initialization of the missile position to where missile direction gets set

I apologize.  I am a little confused.

 

I did notice that I had forgotten to indicate the bit in a couple of the if...thens but in regards to the fire button flag I wasn't sure what you had meant.  I know in the original example you had it as a full variable so I had thought that I could use a single bit for the flag for P1 and a different bit from that variable for P0.

 

I had also tried the initialization of the missile position in other parts of the code but noticed that it would interfere with how the missile fired.

[bogax]

line 283 of the .bas file you posted sets f{1} = 0

so presumably you want a different bit for the fire flag

I've been molesting your code so I'm not sure its right

but this is what I did

not in order

the call to park goes any where the missile is parked not just this excerpt

 

edit:  the way this code is set up, you can only fire if you're moving

         and it fires when you press the fire button not when its released

 

    def park_m0 = gosub pkm0
    def park_m1 = gosub pkm1

pkm0  m0d = 0 : missile0x = 200 : missile0y = 200 : return

pkm1  m1d = 0 : missile1x = 200 : missile1y = 200 : return

 

;BALL
 
 if collision(missile0,player1) then g{0} = 1 : park_m0
 if collision(missile1,player0) then g{1} = 1 : park_m1

;P0 SHOOTING

    if collision(ball,player0) then skip_m0_direction
                     
    pj0f = j0f                               
    if joy0fire then j0f{2} = 1 else j0f{2} = 0    
    if pj0f{2} then skip_m0_direction          
    if !j0f{2} then skip_m0_direction           
    

    m0d = (SWCHA ^ %11111111) / 16           
    if m0d then missile0x = player0x + 3 : missile0y = player0y - 4

skip_m0_direction
    if !m0d then skip_move_m0               

    missile0x = missile0x + mvx[m]
    missile0y = missile0y + mvy[m]

skip_move_m0
 if collision(missile0,playfield) then park_m0

;P1 SHOOTING

    if collision(ball,player1) then goto skip_m1_direction
                     
    pj1f = j1f                               
    if joy1fire then j1f{3} = 1 else j1f{3} = 0    
    if pj1f{3} then skip_m1_direction          
    if !j1f{3} then skip_m1_direction           
    
    m1d = (SWCHA ^ %11111111) & %00001111
    if m1d then missile1x = player1x + 3 : missile1y = player1y - 4

skip_m1_direction
    if !m1d then skip_move_m1               

    missile1x = missile1x + mvx[n]
    missile1y = missile1y + mvy[n]

skip_move_m1
 if collision(missile1,playfield) then park_m1
SKIP_SHOOTING_1

Edited December 14, 2020 by bogax

[KevKelley]

Okay.  I understand!  
 

When I changed the shooting code I forgot I didn't need the bit check on Line 283.  I deleted that along with the other check for f{5} for now and when I get home I will do the other changes.  

 

Thank you again.