Computer Science Canada

Help with projectile collision detection
Author:  Wasabicheese [ Mon May 25, 2009 11:52 am ]
Post subject:  Help with projectile collision detection
Im wondering how tio work projectile collision detection. I've got collsion detection for the characters working, but the projectile collision isnt. Could anybody help me out?
"Blast" is the projectile, here's my code.

Turing:


%Music
process BgmSound
    loop
        Music.PlayFile ("music.mp3")
    end loop
end BgmSound
fork BgmSound

View.Set ("title:Space Survival")

var mDamage, hp, Enemyhp : int
var mypic1 : int := Pic.FileNew ("StrikerRight.bmp")
var mypic2 : int := Pic.FileNew ("Enemy.bmp")
var blast : int := Pic.FileNew ("Blast.bmp")
var CharacterX : array 1 .. 2 of int
var CharacterY : array 1 .. 2 of int
var MonsterX : array 1 .. 2 of int
var MonsterY : array 1 .. 2 of int
var blastX : array 1 .. 2 of int
var blastY : array 1 .. 2 of int
var chars : array char of boolean
var shoot : boolean := false
View.Set ("offscreenonly, graphics:650;410")
CharacterX (1) := 50 % Characters X value (Horizontal Axis)
CharacterY (1) := 50 % Characters Y value (Verticle Axis
CharacterX (2) := 0
CharacterY (2) := 0
MonsterX (1) := 550 % Monsters X value (Horizontal Axis)
MonsterY (1) := 200 % Monsters Y value (Verticle Axis)
MonsterX (2) := 0
MonsterY (2) := 0
blastX (1) := CharacterX (1) + 11
blastY (1) := CharacterY (1) + 11
blastX (2) := 0
blastY (2) := 0
hp := 500
Enemyhp := 2
const Speed := 5

MonsterX (2) := MonsterX (1) + Pic.Width (mypic2)
MonsterY (2) := MonsterY (1) + Pic.Height (mypic2)
blastX (2) := blastX (1) + Pic.Width (blast)
blastY (2) := blastY (1) + Pic.Height (blast)

loop
    drawfillbox (1, 1, maxx, maxx, black)

    drawfillbox (5, 384, hp + 5, 384, red) %Hp bars
    drawfillbox (5, 385, hp + 5, 385, red) %Hp bars
    drawfillbox (5, 386, hp + 5, 386, red) %Hp bars
    drawfillbox (5, 387, hp + 5, 387, red) %Hp bars
    drawfillbox (5, 388, hp + 5, 388, red) %Hp bars
    drawfillbox (5, 389, hp + 5, 389, red) %Hp bars
    drawfillbox (5, 390, hp + 5, 390, red) %Hp bars
    drawfillbox (5, 391, hp + 5, 391, red) %Hp bars
    drawfillbox (5, 392, hp + 5, 392, red) %Hp bars
    drawfillbox (5, 393, hp + 5, 393, red) %Hp bars
    drawfillbox (5, 394, hp + 5, 394, red) %Hp bars
    drawfillbox (5, 395, hp + 5, 395, red) %Hp bars
    drawfillbox (5, 396, hp + 5, 396, red) %Hp bars
    drawfillbox (5, 397, hp + 5, 397, red) %Hp bars
    drawfillbox (5, 398, hp + 5, 398, red) %Hp bars
    drawfillbox (5, 399, hp + 5, 399, red) %Hp bars


    %Collision Detection
    if CharacterX (2) > MonsterX (1) and CharacterX (1) < MonsterX (2) and CharacterY (2) > MonsterY (1) and CharacterY (1) < MonsterY (2) and hp > 0 then
        hp := hp - 2
    end if

    Input.KeyDown (chars)
    if chars (KEY_UP_ARROW) and hp > 0 then
        CharacterY (1) += Speed
        blastX (1) := CharacterX (1) + 11
        blastY (1) := CharacterY (1) + 11
        if CharacterX (2) > MonsterX (1) and CharacterX (1) < MonsterX (2) and CharacterY (2) > MonsterY (1) and CharacterY (1) < MonsterY (2) and hp > 0 then
            hp := hp - 2
        end if
        CharacterY (2) := CharacterY (1) + Pic.Height (mypic1)
        if CharacterY (1) + Pic.Height (mypic1) >= maxy then
            CharacterY (1) := maxy - Pic.Height (mypic1)
        end if
    end if
    if chars (KEY_RIGHT_ARROW) and hp > 0 then
        CharacterX (1) += Speed
        blastX (1) := CharacterX (1) + 11
        blastY (1) := CharacterY (1) + 11
        if CharacterX (2) > MonsterX (1) and CharacterX (1) < MonsterX (2) and CharacterY (2) > MonsterY (1) and CharacterY (1) < MonsterY (2) and hp > 0 then
            hp := hp - 2
        end if
        CharacterX (2) := CharacterX (1) + Pic.Width (mypic1)
        if CharacterX (1) + Pic.Width (mypic1) >= maxx then
            CharacterX (1) := maxx - Pic.Width (mypic1)
        end if
    end if
    if chars (KEY_LEFT_ARROW) and hp > 0 then
        CharacterX (1) -= Speed
        blastX (1) := CharacterX (1) + 11
        blastY (1) := CharacterY (1) + 11
        if CharacterX (2) > MonsterX (1) and CharacterX (1) < MonsterX (2) and CharacterY (2) > MonsterY (1) and CharacterY (1) < MonsterY (2) and hp > 0 then
            hp := hp - 2
        end if
        CharacterX (2) := CharacterX (1) + Pic.Width (mypic1)
        if CharacterX (1) <= 0 then
            CharacterX (1) := 0
        end if
    end if
    if chars (KEY_DOWN_ARROW) and hp > 0 then
        CharacterY (1) -= Speed
        blastX (1) := CharacterX (1) + 11
        blastY (1) := CharacterY (1) + 11
        if CharacterX (2) > MonsterX (1) and CharacterX (1) < MonsterX (2) and CharacterY (2) > MonsterY (1) and CharacterY (1) < MonsterY (2) and hp > 0 then
            hp := hp - 2
        end if
        CharacterY (2) := CharacterY (1) + Pic.Height (mypic1)
        if CharacterY (1) <= 1 then
            CharacterY (1) := 1
        end if
    end if
    if chars (' ') then
        shoot := true
    end if
    if shoot = true then
        blastX (1) += 10
        Pic.Draw (blast, blastX (1), blastY (1), picMerge)
    end if
    if blastX (1) >= maxx and hp > 0 then
        blastX (1) := CharacterX (1) + 11
        blastY (1) := CharacterY (1) + 11
        blastX (2) := 0
        blastY (2) := 0
        shoot := false
        if blastX (2) >= MonsterX (1) and blastX (1) <= MonsterX (2) and blastY (2) >= MonsterY (1) and blastY (1) <= MonsterY (2) and hp >= 0 then
            hp := hp - 2
        end if
    end if

    if hp <= 0 then
        put "You have died" %Hp System
    end if

    View.Set ("offscreenonly")
    Pic.Draw (mypic2, MonsterX (1), MonsterY (1), picMerge) % Enemy
    Pic.Draw (mypic1, CharacterX (1), CharacterY (1), picMerge) % Character
    View.Update
    delay (13)
    cls
end loop



Right now if it works it should drain my characters hp. If anybody could help me out, it would be greatly appreciated.
Author:  Kharybdis [ Tue May 26, 2009 8:01 am ]
Post subject:  RE:Help with projectile collision detection
Can you put ALL of your extra things (like pictures) in a zip folder and attach 'em?
Author:  Wasabicheese [ Tue May 26, 2009 1:33 pm ]
Post subject:  Re: Help with projectile collision detection
ok, here it is
Author:  Kharybdis [ Fri May 29, 2009 5:37 pm ]
Post subject:  RE:Help with projectile collision detection
Use this to see the values every time they hit.. put it before the main loop and type 'fork lol' right as the loop starts

Turing:
process lol   
    put blastY (1)
    put MonsterY (2)
    put blastX (1)
    put MonsterX (1)
    put hp
    delay (1000)
end lol


You have too many 'and' statements that combine to evaluate to false, which is why the hp ain't going down.

I've also noticed that you use very many little arrays. I have no clue why you would do it this way, but since many of your arrays are the same, i suggest you use Types...

Implementation of Types in your code:

Turing:
type generalType : array 1 ..2 of int


and you would assign each array to be like:

Turing:
var CharacterX  : generalType


anyways.. thats just tips on how to help you solve this yourself.
As for your problem...

Turing:
if blastX (1) >= maxx and hp > 0 then
        blastX (1) += CharacterX (1) + 11
        blastY (1) += CharacterY (1) + 11
        blastX (2) := 0
        blastY (2) := 0
        shoot := false
        if blastX (1) >= MonsterX (1) and blastX(2) <= MonsterX(2) and hp >= 0 then
            hp := hp - 1
        end if
    end if


This is how i changed your code when i looked for your error. Main thing you should see is that when the blast hits the monster, your hp will go down indefinitely unless you move your character. That's because its not fully error - trapped (i deleted part of your code that made it only work for a certain part of the screen, thus it will always do it.
Main change is that i changed the assignment statement blastX(1) := CharacterX(1) + 11 to have it add to blastX.
You see, your blastX wasn't actually changing, which was giving you an error...

Try continuing solving your problem by yourself.

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