AmigaBasic/Cando: Point and Click Walking Routine

lifeschool · 29 November 2023, 22:49

Hi there

I've no idea if this is the right place for this.

I'm making a point and click adventure demo using Cando (which is just a front-end for BASIC). When I click on a destination, my character will walk there using the routine below. (which I've added annotations for you)

When I walk Right to Left, the character moves to the exact pixel and stops. But when I move from Left to Right, the character moves a bit too far to the right of my destination, then steps back to the correct place, and stops.

I can't see what I am doing wrong. The routines and the walking frames are mirrored exactly. But why does walking backwards work, but walking forwards doesn't?

Code:

Let Dest=MouseX  ; use the current X positon of the mouse as the destination
Let Count=PX  ; note the current X position of the player and save it to Count

If Room=1
    If Dest>PX and Dest>64   ; anything less than X.64 is blocked on screen 1 
        While Count<Dest and PX=>64   ; while the player X is less than Dest.
            Let PX=PX+18
            Let Count=Count+18
            If Walk=0    ; if the player is stopped, or about to walk, clear screen 
                Do "Draw Backdrop"
            EndIf
             Let Walk=Walk+1  ; increase the walk by 1

             If Walk=1 and PX<208 or Walk=1 and PX>406  ; if the character is visible, show the next frame of walking.
                ShowBrush "pics/w2a.bsh",PX,PY
            EndIf
            If Walk=2 and PX<208 or Walk=2 and PX>406
                ShowBrush "pics/w3a.bsh",PX,PY
            EndIf
            If Walk=3 and PX<208 or Walk=3 and PX>406
                ShowBrush "pics/w4a.bsh",PX,PY
            EndIf
            If Walk=4 and PX<208 or Walk=4 and PX>406
                ShowBrush "pics/w2a.bsh",PX,PY
                Let Walk=1  ;  at the end of the loop, go to frame 2 (walk 2)
            EndIf
            If Count=>Dest and PX<208 or Count=>Dest and PX>406  ; if the walk is over, and character is visible, return to standing.
                ; ShowBrush "pics/w1a.bsh",PX,PY  (this is not needed)
                Let Walk=0
            EndIf
            Do "Draw Backdrop"   ; draw backdrop and standing character
        EndLoop
    EndIf
EndIf

If Room<>1
    If Dest>PX
        While Count<Dest and PX<600
            Let PX=PX+18
            Let Count=Count+18
            If Walk=0
                Do "Draw Backdrop"
            EndIf
            
            Let Walk=Walk+1
            
            If Walk=1
                ShowBrush "pics/w2a.bsh",PX,PY
            EndIf
            If Walk=2
                ShowBrush "pics/w3a.bsh",PX,PY
            EndIf
            If Walk=3
                ShowBrush "pics/w4a.bsh",PX,PY
            EndIf
            If Walk=4
                ShowBrush "pics/w2a.bsh",PX,PY
                Let Walk=1
            EndIf
            If Count=>Dest
                ; ShowBrush "pics/w1a.bsh",PX,PY
                Let Walk=0
            EndIf
            Do "Draw Backdrop"
        EndLoop
    EndIf
EndIf

If Room=1
    If Dest<PX and Dest>64
        While Count>Dest and PX>64
            Let PX=PX-18
            Let Count=Count-18
            If Walk=0
                Do "Draw Backdrop"
            EndIf
            
            Let Walk=Walk+1
            
            If Walk=1 and PX<208 or Walk=1 and PX>406
                ShowBrush "pics/w4b.bsh",PX,PY
            EndIf
            If Walk=2 and PX<208 or Walk=2 and PX>406
                ShowBrush "pics/w3b.bsh",PX,PY
            EndIf
            If Walk=3 and PX<208 or Walk=3 and PX>406
                ShowBrush "pics/w2b.bsh",PX,PY
            EndIf
            If Walk=4 and PX<208 or Walk=4 and PX>406
                ShowBrush "pics/w4b.bsh",PX,PY
                Let Walk=1
            EndIf
            
            If Count=<Dest and PX<208 or Count=<Dest and PX>406
                ; ShowBrush "pics/w1b.bsh",PX,PY
                Let Walk=0
            EndIf
            Do "Draw Backdrop"
        EndLoop
    EndIf
EndIf

If Room<>1
    If Dest<PX
        While Count>Dest
            Let PX=PX-18
            Let Count=Count-18
            If Walk=0
                Do "Draw Backdrop"
            EndIf
            
            Let Walk=Walk+1
            If Walk=1
                ShowBrush "pics/w4b.bsh",PX,PY
            EndIf
            If Walk=2
                ShowBrush "pics/w3b.bsh",PX,PY
            EndIf
            If Walk=3
                ShowBrush "pics/w2b.bsh",PX,PY
            EndIf
            If Walk=4
                ShowBrush "pics/w4b.bsh",PX,PY
                Let Walk=1
            EndIf
            
            If Count=<Dest
                ; ShowBrush "pics/w1b.bsh",PX,PY
                Let Walk=0
            EndIf
            Do "Draw Backdrop"
        EndLoop
    EndIf
EndIf

If Room<>4 and PX=>580   ; if character at edge, scroll screen
    Do "ScrollForwards"
EndIf

If Room<>1 and PX=<50   ; if character at left edge, scroll screen
    Do "ScrollBackwards"
EndIf

Video
[ Show youtube player ]

aNdy/AL/COS · 30 November 2023, 13:53

I've never used AmigaBasic or CanDo, but have used other languages to make a few games, so I'm guessing as to your problem (if I'm reading your question correctly) based on my experiences over the years.

It sounds like to me that when you're adding to your current X position to move right, it eventually exceeds your maximum X so then steps backwards. When subtracting to move left, it just happens that your current X position matches the minimum X so it 'works'.

If this is the case, then I see two solutions...

(1) Before moving your character, do an X calculation and store in a temporary variable that you can use to compare to max and min X and make decisions from there. Using rough pseudo-code, something like this...

Code:

CURRENT_X + MOVE = TEMP_X

IF TEMP_X >= MAX_X
 CURRENT_X = MAX_X
ELSE
 CURRENT_X = TEMP_X
ENDIF

PRINT CHARACTER_POSITION AT CURRENT_X

I would also do this check for left movement, even if it appears to be working correctly.

(2) Set your minimum and maximum X values to be exactly divisible by the X movement of your character so the values are never exceeded. You would also have to factor in the mouse position x and round up/down to those divisible values. Could get messy!

I would favour solution (1). Make the code do the work so if anything else changes later on such as you changing the starting position of the character, you don't end up having to work out stuff yourself and adjust.

Hopefully that makes sense and if I've misread your question, apologies for wasting your time!

lifeschool · 30 November 2023, 19:13

Thanks for your tips. In the end, I added a check after moving Player_X. It seems to work a lot better than before.

Code:

If Room=1
    If Dest>PX and Dest>64
        While Count<Dest and PX=>64
            Let PX=PX+18
>            If PX=>Dest
>                Let Count=Dest
>                Let PX=Dest
>                Let Walk=0
>            Else
>                Let Count=Count+18
>            EndIf
>            If Walk=0 and Count<>Dest
                Do "Draw Backdrop"
            EndIf
            Let Walk=Walk+1
            If Walk=1 and PX<208 or Walk=1 and PX>406
                ShowBrush "pics/w2a.bsh",PX,PY
            EndIf
            If Walk=2 and PX<208 or Walk=2 and PX>406
                ShowBrush "pics/w3a.bsh",PX,PY
            EndIf
            If Walk=3 and PX<208 or Walk=3 and PX>406
                ShowBrush "pics/w4a.bsh",PX,PY
            EndIf
            If Walk=4 and PX<208 or Walk=4 and PX>406
                ShowBrush "pics/w2a.bsh",PX,PY
                Let Walk=1
            EndIf
            If Count=>Dest and PX<208 or Count=>Dest and PX>406
                ; ShowBrush "pics/w1a.bsh",PX,PY
                Let Walk=0
            EndIf
            Do "Draw Backdrop"
        EndLoop
    EndIf
EndIf

aNdy/AL/COS · 30 November 2023, 23:01

Glad you solved your problem!

Retro1234 · 01 December 2023, 00:33

You could try GRAC

Samurai_Crow · 01 December 2023, 03:16

GRAC 2&3 are written in AmosPro (another BASIC) and source to version 2 is on Aminet. Walk zones are difficult to program but I could offer advice if you like.

lifeschool · 01 December 2023, 17:30

Thanks for the advice everyone.

I have used GRAC before, and I'm perhaps the only person on this planet using CanDo, but it is a pleasure to use it, and I'm not technical enough to use Blitz etc.

My previous games are Holiday, and Beat Cancer/Empire Protector. All made with CanDo.
https://lifeschool22.itch.io/

The walk routine is easy with Cando, just make a hit box as wide as the screen and activate the walking script on click. It's very easy.

Another issue I'm having with my walking script for room 1 is the character pops up after walking past the cabin. The character refuses to appear until the end of the walk, and then it pops up and stops. I guess one way would be to have a bitmap of the cabin over the top, so the character is hidden, but the character still appears for a milli second each frame, until the bitmap is layed over it each time, unless I blank the walk during that section.

desiv · 01 December 2023, 19:39

Interesting...
I'd heard of CanDo, but had no idea it basically ;-) used Amiga BASIC on the backend...

Have to admit I really liked line numbered BASICs and when I got my Amiga, was a bit disappointed when I fired up AmigaBASIC...

Then I decided if I was going to lose line numbers, I'd jump to C... ;-)

Great work!!!

Etze · 01 December 2023, 20:51

Quote:

Originally Posted by desiv

Interesting...
I'd heard of CanDo, but had no idea it basically ;-) used Amiga BASIC on the backend...

Nah, it doesn’t. It’s just a Basic-like language (with many differences to „modern standard“ Basic).

lifeschool · 02 December 2023, 00:57

@desiv, didn't you used to have a penguin avatar? Yes C would be more ideal for coding, but it was always too complex for me. CanDo is like a GRAC for anything. I've seen dual-pane directory browsers made with it, spreadsheets and database etc, but it can also use basic commands.

It seems it is not true BASIC after all, but for the sake of If's and While's, and Let's, it is the same coding. Instead of GoSub, there is the command Do. It seems there are line numbers in the CanDo editor, but they are not supported for GoTo commands, and instead it jumps to defined 'bookmarks' I think?

desiv · 02 December 2023, 03:25

Quote:

Originally Posted by lifeschool

@desiv, didn't you used to have a penguin avatar?

Yeah, what happened to that Avatar? Didn't notice it was gone.
Now I have to find it again... ;-)
(Fixed!!! Whew! Made that avatar over 20 years ago now! Well, added the boing to someone else's penguin that is..)

OK, not AmigaBASIC, but yeah, very BASIC like in that scripting language...

Cobe · 03 December 2023, 23:20

Nice! Its intresting to see what could be done with cando.
Once before I used cando or was it amigavision? to make a simple Where's Wally "game".
Then I jumped to Blitz. Its not that harder. You should try. Though your project isnt that easy...

lifeschool · 17 December 2023, 02:34

Well here it is, or at least the demo of the prototype.

https://lifeschool22.itch.io/monkeye...-os3cando-demo

This 3 screen mini game is finished but still contains a few bugs. I included the source code, if people want to play about with it.
This was basically a proof of concept, although the objects flash, so really, it was a failed attempt. But anyway...

I can also share the source of my other two games if anyone is interested.

30 November 2023, 13:53	#2
aNdy/AL/COS Registered User Join Date: Jan 2022 Location: Wales Posts: 91	I've never used AmigaBasic or CanDo, but have used other languages to make a few games, so I'm guessing as to your problem (if I'm reading your question correctly) based on my experiences over the years. It sounds like to me that when you're adding to your current X position to move right, it eventually exceeds your maximum X so then steps backwards. When subtracting to move left, it just happens that your current X position matches the minimum X so it 'works'. If this is the case, then I see two solutions... (1) Before moving your character, do an X calculation and store in a temporary variable that you can use to compare to max and min X and make decisions from there. Using rough pseudo-code, something like this... Code: CURRENT_X + MOVE = TEMP_X IF TEMP_X >= MAX_X CURRENT_X = MAX_X ELSE CURRENT_X = TEMP_X ENDIF PRINT CHARACTER_POSITION AT CURRENT_X I would also do this check for left movement, even if it appears to be working correctly. (2) Set your minimum and maximum X values to be exactly divisible by the X movement of your character so the values are never exceeded. You would also have to factor in the mouse position x and round up/down to those divisible values. Could get messy! I would favour solution (1). Make the code do the work so if anything else changes later on such as you changing the starting position of the character, you don't end up having to work out stuff yourself and adjust. Hopefully that makes sense and if I've misread your question, apologies for wasting your time!

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30 November 2023, 23:01	#4
aNdy/AL/COS Registered User Join Date: Jan 2022 Location: Wales Posts: 91	Glad you solved your problem!

01 December 2023, 00:33	#5
Retro1234 Phone Homer Join Date: Jun 2006 Location: 5150 Posts: 5,778	You could try GRAC

01 December 2023, 03:16	#6
Samurai_Crow Total Chaos forever! Join Date: Aug 2007 Location: Waterville, MN, USA Age: 49 Posts: 2,187	GRAC 2&3 are written in AmosPro (another BASIC) and source to version 2 is on Aminet. Walk zones are difficult to program but I could offer advice if you like.

01 December 2023, 17:30	#7
lifeschool Local Moderator Join Date: Oct 2009 Location: Lancashire, UK Age: 48 Posts: 1,597	Thanks for the advice everyone. I have used GRAC before, and I'm perhaps the only person on this planet using CanDo, but it is a pleasure to use it, and I'm not technical enough to use Blitz etc. My previous games are Holiday, and Beat Cancer/Empire Protector. All made with CanDo. https://lifeschool22.itch.io/ The walk routine is easy with Cando, just make a hit box as wide as the screen and activate the walking script on click. It's very easy. Another issue I'm having with my walking script for room 1 is the character pops up after walking past the cabin. The character refuses to appear until the end of the walk, and then it pops up and stops. I guess one way would be to have a bitmap of the cabin over the top, so the character is hidden, but the character still appears for a milli second each frame, until the bitmap is layed over it each time, unless I blank the walk during that section.

01 December 2023, 19:39	#8
desiv Registered User Join Date: Oct 2009 Location: Salem, OR Posts: 1,770	Interesting... I'd heard of CanDo, but had no idea it basically ;-) used Amiga BASIC on the backend... Have to admit I really liked line numbered BASICs and when I got my Amiga, was a bit disappointed when I fired up AmigaBASIC... Then I decided if I was going to lose line numbers, I'd jump to C... ;-) Great work!!!

02 December 2023, 00:57	#10
lifeschool Local Moderator Join Date: Oct 2009 Location: Lancashire, UK Age: 48 Posts: 1,597	@desiv, didn't you used to have a penguin avatar? Yes C would be more ideal for coding, but it was always too complex for me. CanDo is like a GRAC for anything. I've seen dual-pane directory browsers made with it, spreadsheets and database etc, but it can also use basic commands. It seems it is not true BASIC after all, but for the sake of If's and While's, and Let's, it is the same coding. Instead of GoSub, there is the command Do. It seems there are line numbers in the CanDo editor, but they are not supported for GoTo commands, and instead it jumps to defined 'bookmarks' I think?

03 December 2023, 23:20	#12
Cobe Registered User Join Date: Jan 2014 Location: Belgrade / Serbia Age: 41 Posts: 1,004	Nice! Its intresting to see what could be done with cando. Once before I used cando or was it amigavision? to make a simple Where's Wally "game". Then I jumped to Blitz. Its not that harder. You should try. Though your project isnt that easy...

17 December 2023, 02:34	#13
lifeschool Local Moderator Join Date: Oct 2009 Location: Lancashire, UK Age: 48 Posts: 1,597	Well here it is, or at least the demo of the prototype. https://lifeschool22.itch.io/monkeye...-os3cando-demo This 3 screen mini game is finished but still contains a few bugs. I included the source code, if people want to play about with it. This was basically a proof of concept, although the objects flash, so really, it was a failed attempt. But anyway... I can also share the source of my other two games if anyone is interested.

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