File content as of revision 8:19dd2a538cbe:

#include "Vector.h"

Vector::Vector()
{   // constructor
    this->set((float)0,(float)0);
}

Vector::Vector(float fX, float fY)
{
    this->set(fX, fY);
}

void Vector::set(float fX, float fY)
{
    x=fX;
    y=fY;
}
void Vector::set(int nX, int nY)
{
    this->set((float)nX, (float)nY);
}

float Vector::getSize()
{   // get the size of the vector
    return(sqrt(x*x+y*y));
}

bool Vector::isLeft()  { return(x<0); }
bool Vector::isRight() { return(x>0); }
bool Vector::isUp()    { return(y<0); }
bool Vector::isDown()  { return(y>0); }


void Vector::add(float fAdd)
{   // add the size of the vector by adding to its size
    float fSize=getSize();
    float fSizeNew=fSize+fAdd;
    if(fSize!=0)
    {
        x=x * (fSizeNew/fSize);
        y=y * (fSizeNew/fSize);
    }
    else
    {   // in case of zero lenght, default to addition in first quadrant.
        x=sqrt(0.5 * fAdd * fAdd);
        y=x;
    }
}

void Vector::add(Vector vAdd)
{
    x+=vAdd.x;
    y+=vAdd.y;
}

void Vector::multiply(Vector vMult)
{   // multiply the vector by means of the other vector
    x*=vMult.x;
    y*=vMult.y;
}

Vector Vector::getNormalized()
{   // get the Unit vector (= vector normalized to length 1)
    // see http://en.wikipedia.org/wiki/Unit_vector
    return(Vector(x/getSize(), y/getSize()));
}

Vector Vector::getNormal()
{   // get the normal Vector
    // see http://stackoverflow.com/questions/14885693/how-do-you-reflect-a-vector-over-another-vector
    // vec.leftNormal --> vx = vec.vy; vy = -vec.vx; 
    // vec.rightNormal --> vx = -vec.vy; vy = vec.vx;
    if(isLeft())
        return(Vector(y, -1 * x));
    else
        return(Vector(-1 * y, x));
}
    
void Vector::bounce(Vector vBounce)
{   // bounce a vector against another vector
    // see http://stackoverflow.com/questions/14885693/how-do-you-reflect-a-vector-over-another-vector
    Vector vBounceNormalized=vBounce.getNormalized();
    Vector vBounceNormal=vBounce.getNormal();
    Vector vBounceNormalNormalized=vBounceNormal.getNormalized();

    // 1. Find the dot product of vec1 and vec2
    // Note: dx and dy are vx and vy divided over the length of the vector (magnitude)
    float dpA = x * vBounceNormalized.x + y * vBounceNormalized.y;

    // 2. Project vec1 over vec2
    float prA_vx = dpA * vBounceNormalized.x;
    float prA_vy = dpA * vBounceNormalized.y;

    // 3. Find the dot product of vec1 and vec2's normal
    float dpB = x * vBounceNormalNormalized.x + y * vBounceNormalNormalized.y;

    // 4. Project vec1 over vec2's left normal
    float prB_vx = dpB * vBounceNormalNormalized.x;
    float prB_vy = dpB * vBounceNormalNormalized.y;

    // 5. Add the first projection prA to the reverse of the second -prB
    float new_vx = prA_vx - prB_vx;
    float new_vy = prA_vy - prB_vy;
    set(new_vx, new_vy);
}