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Thread: Sprite Engine Collision, cmRadius , always colliding

  1. #1

    Sprite Engine Collision, cmRadius , always colliding

    Hello everyone ,

    It's been a while, anyway I decided I go another round with the sprite engine and asphyre , and finally I did my breakthrough , smooth scrolling is working now, I was scrolling the world in a way in which it was not meant to be scrolled.
    Once I'm done with my latest findings, I will collect my documents and do a more detailed step-by-step guide thing.

    Anyway the problem I am facing now is this :

    OnFormCreate after I initialize the Apshyre Device , I create the Player Ship, then I create a test enemy , that is only moving left and right ... like this
    Code:
         Enemy := TEnemy.Create(SpriteEngine);
        with TEnemy(Enemy) do
            begin
                ImageName := 'Enemy.image';
                Z := 40;
                X := 100;
                y := 4350;
                horz := 1;
                CollideMethod := cmRadius;
                CollideRadius := 5;
                DoCollision := true;
            end;
    ** the Enemy size is 32x64 , I guess the collide radius means that it checks Enemy.X,Enemy.Y +5 radius (circle) for collision...

    Now using PlayerSprite.Move I move the ship , I can shoot (create Bullet sprites) like this :

    Code:
     procedure TPlayerSprite.Move(const MoveCount: Single);
    var Bullet : TBullet;
    begin
    // here we move the ship and the world with world.y
         inherited;
         if Engine.WorldY > 0 then
            Y := Y - 0.5; // we are moving constantly ahead till we reach the end
        if Form1.Keyboard.Key[203] then
         begin
              if X > 0 then
                X := X - 3
              else
                X := 0; // we put the ship to the edge of the screen
         end;
         if Form1.Keyboard.Key[205] then
         begin
              if X < 608 then
                X := X + 3
              else
                X := 608; // we put the ship to the edge of the screen
         end;
        if fireRate > 1 then dec(fireRate);
        if ((Form1.Keyboard.Key[29]) or (Form1.Keyboard.Key[57])) and (firerate=1) then
           begin
             Bullet := TBullet.Create(Form1.SpriteEngine);
             Bullet.CollideMethod := cmRadius;
             Bullet.CollideRadius := 5;
             Bullet.DoCollision:=true;
             Bullet.MoveSpeed := 7;
             Bullet.DoCenter := False;
             Bullet.X := PlayerSprite.X;
             Bullet.Y := PlayerSprite.Y + 10;
             Bullet.Z := PlayerSprite.Z;
             Bullet.ImageName := 'Bullet.image';
             firerate:=20;
           end;
         Engine.WorldY := Y - (480-64);
    end;
    And then I move the Bullet and the Enemy sprite and check for collision like this :

    Code:
     procedure TEnemy.Move( const MoveCount: Single);
    begin
        inherited;
        y:=Engine.WorldY+64;
        x:=x+horz;
        if x > 640 then horz:=horz*-1;
        if x < 0 then horz:=horz*-1;
    end;
    
    procedure TBullet.Move(const MoveCount: Single);
    begin
         inherited;
         Y := Y - FMoveSpeed;
         if Y < WorldY then
         begin
              Dead;
              Visible := False;
         end;
         Collision;
    end;
    
    procedure TBullet.OnCollision(const Sprite: TSprite);
    begin
         if (Sprite is TEnemy) then
            begin
                 Dead;
            end;
    end;
    The problem is the newly created Bullet sprites are instantly colliding with the TEnemy sprite , and thus as long as the TBullet.OnCollision is
    not commented out, Bullet's aren't visible...
    They are not colliding properly , what am I doing wrong here ? Any ideas? I was banging my head against the wall all day long, trying to check samples
    but unfortunately they use another newer Sprite Engine...

    Please Help.

    Greetings
    Robert

  2. #2
    Hi,

    I solved it, forgot for both Bullet and Enemy movement
    Code:
     CollidePos := Point2(X, Y);
    Though I will need to modify this... CollidePos is supposed to be the center of the enemy?
    For example if I have a 32x64 enemy, the correct colidepos would be 16,32 ? and there I would set a radius of 32...
    And would create the illusion that the enemy is only destroyed if the middle of it is hit... which I think is perfectly fine, I think Jamestown used this method for
    the player ship, not sure if it was meant like this by design, or if it was just a shortcut with using Radius collision...

    Wow can't believe this, we are going somewhere... once I'm done I'll post the entire project step-by-step ... how I did it .

    Greetings
    Robert

  3. #3
    Glad to see you are progressing.

  4. #4
    This forum has a positive effect on me just by posting here I sometimes solve my own problems...

    ... and I also took a 3 hour walk in the City to clear my head.... after that ...it just hit me...

    CollisionPos is always the center of the sprite I'm checking for collision, and I must update it onMove ,...because it is constantly moving... makes sense now.
    Also radius for a circle that fits into a 32x32 square is 16...that works to now.

    I did the Editor, now I'm working in Lazarus IDE . I've cut back on a lot of features, last time I think I did the huge mistake of wanting to do everything at once, and dying painfully in the end.

    My current goals are, scrolling map, waves of enemies coming at me , firing at enemies, enemies have different hit points some take 1 hit, some 2 or 3... my ship has 3 lifes...

    I enemy ship type 1 gives 25 point , type 2 50 etc.... every 1000 points you get an extra life... game will have I hope 3-4 levels...
    A nice menu...with information...I'm thinking about doing a comic style briefing before each mission, nothing to fancy...

    Right now with the scrolling done, and the collision working, I have everything but the artwork...

    so I'm drawing right now.

    Level01 is done, going from Earth to Moon Base...

    Greetings
    Rob

  5. #5
    Welcome back Robert
    Glad to hear it is working so far

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