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  Solved - Bouncing an enemy  (Read 485 times)
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Offline StonePickaxes

JGO Coder


Medals: 4
Projects: 2


Nathan Kramber


« Posted 2011-12-14 22:01:11 »

EDIT - Never mind, figured it out. It feels so good to solve a problem on your own Smiley

I am trying to bounce an enemy across walls. However, my code is working as planned.

Here it is -

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if (x >= 750) 
      {
         x = 749;
         newDirection = true;
      }
     
      if (x <= 10)
      {
         x = 11;
         newDirection = true;
      }
     
      if (y == 480)
      {
         y = 479;
         newDirection = true;
      }
     
      if (y == 10)
      {
         y = 11;
         newDirection = true;
      }
     
      if (newDirection)
      {        
         if ((dx == 1) && (dy == 1))
         {
            if (y == 479) dx = -1;
            if (x == 749) dy = -1;
         }
         
         if ((dx == 1) && (dy == -1))
         {
            if (y == 479) dx = -1;
            if (x == 11) dy = 1;
         }
         
         if ((dx == -1) && (dy == 1))
         {
            if (y == 11) dx = 1;
            if (x == 749) dy = -1;
         }
         
         if ((dx == -1) && (dy == -1))
         {
            if (y == 11) dx = 1;
            if (x == 11) dy = 1;
         }
         newDirection = false;
      }
     
      x = x + dx;
      y = y + dy;


Any help would be appreciated.

Check out my website!
Offline Embedded

Junior Member


Medals: 1



« Reply #1 - Posted 2011-12-14 22:11:33 »

Instread of the whole new direction thing just if x<whatever then make dx=-dx to move in the opposite direction
Offline Danny02
« Reply #2 - Posted 2011-12-14 22:41:09 »

want to offer some tips also:

  • avoid magic nummbers, create some fields or constants which hold such values like your map min max
  • way to much reduant code. everytime u see in your code repeating patters, in moste cases, something is wrong(very bad coding style).
  • try to use more expressiv variable naming


tryed me on a cleaner version, perhaps you find it helpfull
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static final int X_MAX = 750;
static final int X_MIN= 10;
static final int X_MAX= 480;
static final int Y_MIN= 10;

int positionX, positionY;
int velocityX, velocityY;

...

void applyVelocity()
{
    positionX += velocityX;
    positionY += velocityY;

    if(isOutsideBorder(X_MIN, X_MAX, positionX))
    {
        positionX = getReflection(velocityX < 0 ? X_MIN : X_MAX, positionX);
        velocityX *= -1;
    }

    if(isOutsideBorder(Y_MIN, Y_MAX, positionY))
    {
        positionY = getReflection(velocityY < 0 ? Y_MIN : Y_MAX, positionY);
        velocityY *= -1;
    }
}

bool isOutsideBorder(int min, int max, value)
{
    return (value> max | value < min);
}

int getReflection(int center, int value)
{
       return 2 * center - value;
}

...

<- ps: don't like this anyway(have it so un ObjectOrientated), so why not use a 2D array for the data. Makes it extentable for 3D and saves you 11 lines of code.


also a perhaps more OO way
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static final Area MAP_AREA= new Area(10, 10, 750, 480);
static final BorderRestriction  RESTRICTION = Reflection;

Vector2 position, velocity;

...

void applyVelocity()
{
    position.add(velocity);
    RESTRICTION.apply(position, velocity, MAP_AREA);
}

..

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