The tip in this article will help any beginning game programmer to easily design and use game levels for his Liberty/Just BASIC sprite games. There is no complex programming needed. Once you learn the technique you can design your level in about 5 min! (Not including sprites). It’s easy to do using your mouse and a small design program that I have put together for you.
The steps are broken down as follows:
1)Load a background BMP into the program. 2)Use your mouse to draw out the boundaries for the level. 3)Save the level as an .lvl file (basic text file) to be used in your Game. 4)Use a small programming routine in your game to check for collisions.
First, copy and past the program below into your Liberty/Just BASIC code editor window, save and run the program.
Dim X(5000) 'this can be adjusted to fit your boundary needs
Dim Y(5000)
sz=5 'used to determine the cushion for detecting collisions
nomainwin
WindowWidth=800 'these can be changed to match your background image size
WindowHeight=600
UpperLeftX=int((DisplayWidth-WindowWidth)/2)
UpperLeftY=int((DisplayHeight-WindowHeight)/2)
menu #main,"File","New",[new],"Open",[open],"Save",[save],|,"Test",[test],|,"Exit",[exit]
open "Boundary Designer" for graphics_nsb as #main
print #main,"Down;size ";sz;";color red";
print #main,"trapclose [exit]"
[main.loop]
wait
[new]
filedialog "Open BMP Background","*.bmp",bitmapName$
if bitmapName$<>"" then
loadbmp "bg",bitmapName$
end if
[check]
print #main,"set ";MouseX;" ";MouseY
if MouseX<>X(cnt-1) or MouseY<>Y(cnt-1) then
X(cnt)=MouseX
Y(cnt)=MouseY
cnt=cnt+1
end if
goto [main.loop]
[save]
filedialog "Save level file", "*.lvl", fileName$
open fileName$ for output as #1
for x=1 to cnt-1
tX=X(x)
tY=Y(x)
print #1,tX
print #1,tY
next x
close #1
notice "File saved."
goto [main.loop]
[exit]
close #main
end
[open]
print #main,"when mouseMove ";
print #main,"when leftButtonMove";
filedialog "Select file","*.lvl",fileName$
if fileName$="" then [main.loop]
cnt=1
open fileName$ for input as #2
while eof(#2)<>-1
line input #2,tX
line input #2,tY
X(cnt)=tX
Y(cnt)=tY
cnt=cnt+1
wend
close #2
print #main,"cls;color red"
for d=1 to cnt-1
print #main,"set ";X(d);" ";Y(d)
next d
print #main,"flush"
[test.hit]
for t=1 to cnt-1
'I've made the dots bigger by adding and subracting sz value from each point.
'This makes it easier to hit the line
if MouseX >=X(t)-sz and MouseX <=X(t)+sz and MouseY >=Y(t)-sz and MouseY<=Y(t)+sz then
print #main,"color blue;set ";MouseX;" ";MouseY
t=cnt-1
end if
next t
goto [main.loop]
Run the program and load any BMP file onto the graphic screen. If you can, use a background graphic you want to use in your game. Once you have your background loaded you can begin drawing your boundaries on top of your background. Press and hold the left mouse button to draw on your background. Release the button to stop drawing. You can begin drawing again anywhere on your picture. You will want to draw slowly so the program can capture your mouse locations.
Once your boundaries are all drawn you can test them by selecting File-Test from the File menu. This will switch to test mode and you will no longer be able to draw. You will be able to collide your mouse location with any of the boundaries you have drawn on your background. When your mouse location collides with a boundary you should see your mouse location turn blue. This indicates that you have collided with that boundary. Again you can not move your mouse too fast or it will skip over the boundary and not get detected.
When you have completed drawing your boundary you can save it as a .lvl file. The .lvl file is just a text file with the extension of .lvl. I use this extension to distinguish the file from other file types. You can change this to another extension if you wish. The file contains all the positions on the graphic screen that we designated as boundaries. Once you have saved the file, you can use the file in your game with just a small amount of code.
Using the boundary file in your game is really simple to do. First you must open and load the file into an array. You can add this code to your game level load routine.
Dim X(5000) ‘5000 can be changed if you need less or more
Dim Y(5000) cnt=1 ‘setup up loop counter cush=5 Open “level.lvl” for input as #lvl
While eof(#lvl)=0 line input #lvl,tX line input #lvl,tY X(cnt)=tX Y(cnt)=tY cnt=cnt+1 wend
close #lvl ‘close file
Once the file is loaded into the array you can check for collisions by adding the following code to your [draw] loop. Here is an example of a draw loop I have used in my game. The code below was designed to be used with one sprite on the game screen. Please note that the more sprites you add to the current level, the longer this loop will take to complete. I have not maxed out this code so I can not say what the limit of sprites is at this time. The routine would also have to be recoded in order to check each sprite on your level. You may only need to check for the player's sprite if the other sprites have a pre determined programmed path.
[draw] 'check for crash print #main ,"spritexy? ship1 sx sy"
‘ This loop will quickly check if my boundary position is inside the position of a sprite. ‘You can switch this, if you rather reverse the check. ‘You can also remove thecushfrom the if then line if you wish.
for t=0 to cnt-1 if X(t)-cush>= (sx+20) and X(t)+cush<= (sx+45) and Y(t)-cush>=(sy+20) and Y(t)+cush<=(sy+70) then print #main,"spritemovexy ship1 0 0"; t=cnt-1 hit=1 EXIT FOR end if next t
if hit=1 then notice “You’ve hit something!” end if
This is basically all there is to creating simple boundaries for your sprites. This is a simple technique that can be used in your games until you become more experienced with Liberty/Just BASIC and find more sophisticated methods of collision detection for boundaries.
You can find a game I created named Pirate Escape that uses this method on the LB Downloads file depot under Games. You can contact me at ben_jimenez@yahoo.com with any questions or comments.
benjamin805
Jun 23, 2007
The tip in this article will help any beginning game programmer to easily design and use game levels for his Liberty/Just BASIC sprite games. There is no complex programming needed. Once you learn the technique you can design your level in about 5 min! (Not including sprites). It’s easy to do using your mouse and a small design program that I have put together for you.
The steps are broken down as follows:
1) Load a background BMP into the program.
2) Use your mouse to draw out the boundaries for the level.
3) Save the level as an .lvl file (basic text file) to be used in your Game.
4) Use a small programming routine in your game to check for collisions.
First, copy and past the program below into your Liberty/Just BASIC code editor window, save and run the program.
Dim X(5000) 'this can be adjusted to fit your boundary needs
Dim Y(5000)
sz=5 'used to determine the cushion for detecting collisions
nomainwin
WindowWidth=800 'these can be changed to match your background image size
WindowHeight=600
UpperLeftX=int((DisplayWidth-WindowWidth)/2)
UpperLeftY=int((DisplayHeight-WindowHeight)/2)
menu #main,"File","New",[new],"Open",[open],"Save",[save],|,"Test",[test],|,"Exit",[exit]
open "Boundary Designer" for graphics_nsb as #main
print #main,"Down;size ";sz;";color red";
print #main,"trapclose [exit]"
[main.loop]
wait
[new]
filedialog "Open BMP Background","*.bmp",bitmapName$
if bitmapName$<>"" then
loadbmp "bg",bitmapName$
end if
#main,"drawbmp bg 0 0;flush"
cnt=1
redim X(5000)
redim Y(5000)
print #main,"color red"
print #main,"when mouseMove";
print #main,"when rightButtonUp";
print #main,"when leftButtonMove [check]";
print #main,"setfocus"
goto [main.loop]
[check]
print #main,"set ";MouseX;" ";MouseY
if MouseX<>X(cnt-1) or MouseY<>Y(cnt-1) then
X(cnt)=MouseX
Y(cnt)=MouseY
cnt=cnt+1
end if
goto [main.loop]
[save]
filedialog "Save level file", "*.lvl", fileName$
open fileName$ for output as #1
for x=1 to cnt-1
tX=X(x)
tY=Y(x)
print #1,tX
print #1,tY
next x
close #1
notice "File saved."
goto [main.loop]
[exit]
close #main
end
[open]
print #main,"when mouseMove ";
print #main,"when leftButtonMove";
filedialog "Select file","*.lvl",fileName$
if fileName$="" then [main.loop]
cnt=1
open fileName$ for input as #2
while eof(#2)<>-1
line input #2,tX
line input #2,tY
X(cnt)=tX
Y(cnt)=tY
cnt=cnt+1
wend
close #2
print #main,"cls;color red"
for d=1 to cnt-1
print #main,"set ";X(d);" ";Y(d)
next d
print #main,"flush"
goto [main.loop]
[test]
notice "Right click to stop testing"
print #main,"when leftButtonMove";
print #main,"when mouseMove [test.hit]";
print #main,"when rightButtonUp [end.test]";
goto [main.loop]
[test.hit]
for t=1 to cnt-1
'I've made the dots bigger by adding and subracting sz value from each point.
'This makes it easier to hit the line
if MouseX >=X(t)-sz and MouseX <=X(t)+sz and MouseY >=Y(t)-sz and MouseY<=Y(t)+sz then
print #main,"color blue;set ";MouseX;" ";MouseY
t=cnt-1
end if
next t
goto [main.loop]
[end.test]
print #main,"when mouseMove";
print #main,"when rightButtonUp";
print #main,"when leftButtonMove [check]";
print #main,"color red";
notice "Testing complete"
goto [main.loop]
Run the program and load any BMP file onto the graphic screen. If you can, use a background graphic you want to use in your game. Once you have your background loaded you can begin drawing your boundaries on top of your background. Press and hold the left mouse button to draw on your background. Release the button to stop drawing. You can begin drawing again anywhere on your picture. You will want to draw slowly so the program can capture your mouse locations.
Once your boundaries are all drawn you can test them by selecting File-Test from the File menu. This will switch to test mode and you will no longer be able to draw. You will be able to collide your mouse location with any of the boundaries you have drawn on your background. When your mouse location collides with a boundary you should see your mouse location turn blue. This indicates that you have collided with that boundary. Again you can not move your mouse too fast or it will skip over the boundary and not get detected.
When you have completed drawing your boundary you can save it as a .lvl file. The .lvl file is just a text file with the extension of .lvl. I use this extension to distinguish the file from other file types. You can change this to another extension if you wish. The file contains all the positions on the graphic screen that we designated as boundaries. Once you have saved the file, you can use the file in your game with just a small amount of code.
Using the boundary file in your game is really simple to do. First you must open and load the file into an array. You can add this code to your game level load routine.
Dim X(5000) ‘5000 can be changed if you need less or more
Dim Y(5000)
cnt=1 ‘setup up loop counter
cush=5
Open “level.lvl” for input as #lvl
While eof(#lvl)=0
line input #lvl,tX
line input #lvl,tY
X(cnt)=tX
Y(cnt)=tY
cnt=cnt+1
wend
close #lvl ‘close file
Once the file is loaded into the array you can check for collisions by adding the following code to your [draw] loop. Here is an example of a draw loop I have used in my game. The code below was designed to be used with one sprite on the game screen. Please note that the more sprites you add to the current level, the longer this loop will take to complete. I have not maxed out this code so I can not say what the limit of sprites is at this time. The routine would also have to be recoded in order to check each sprite on your level. You may only need to check for the player's sprite if the other sprites have a pre determined programmed path.
[draw] 'check for crash
print #main ,"spritexy? ship1 sx sy"
‘ This loop will quickly check if my boundary position is inside the position of a sprite.
‘You can switch this, if you rather reverse the check.
‘You can also remove the cush from the if then line if you wish.
for t=0 to cnt-1
if X(t)-cush>= (sx+20) and X(t)+cush<= (sx+45) and Y(t)-cush>=(sy+20) and Y(t)+cush<=(sy+70) then
print #main,"spritemovexy ship1 0 0";
t=cnt-1
hit=1
EXIT FOR
end if
next t
if hit=1 then
notice “You’ve hit something!”
end if
This is basically all there is to creating simple boundaries for your sprites. This is a simple technique that can be used in your games until you become more experienced with Liberty/Just BASIC and find more sophisticated methods of collision detection for boundaries.
You can find a game I created named Pirate Escape that uses this method on the LB Downloads file depot under Games. You can contact me at ben_jimenez@yahoo.com with any questions or comments.