struct CVector 
{
float x,y,z;
}

CVector calculateNormal(CVector vec[])
{
    CVector vector1;        // create a new vector

    CVector vector2;        // and another

    CVector vector3;        // one more...

    
    vector1 = subtract(vec[0],vec[1]);    // v1-v2

    vector2 = subtract(vec[1],vec[2]);    // v2-v3

    
    // now get the cross product (length)

    vector3 = crossProduct(vector1, vector2);
    
    // get the square root of the length

    float length = sqrt(    (vector3.x*vector3.x) +
                            (vector3.y*vector3.y) +
                            (vector3.z*vector3.z) 
                        );
    
    // now calculate the normal of this triangle!

    vector3.x /= length;                  
    vector3.y /= length;
    vector3.z /= length;
    
    // return the Normal!

    return vector3;
}

float dotProduct(CVector vec1, CVector vec2) 
{
			 //    (V1.x * V2.x        +        V1.y * V2.y        +        V1.z * V2.z)

	return ( (vec1.x * vec2.x) + (vec1.y * vec2.y) + (vec1.z * vec2.z) );
}

bool planeCollision(CVector vec[], CVector point)
{
    // vec[] is an array of vertices defining our triangle, point is a random point we are 

    // checking to see if it lies on our plane.

    // ooooh this is an evil equation, very evil, forget learning it as its TOO EVIL!

    
	CVector vector;	// for our "plane" normal

	
	vector = calculateNormal(vec);	// calculate our "planes" normal


	// calculate D from the plane equation

	// D = dot product of our planes normal and a point we know is on that plane...

	float D = -dotProduct(vector, point);		
	    
    // now we have 4 very EVIL values, now we check them in the equation with the vertices

    // of our random point (CVector point)

    // simply return the value, in the main function we check by asking - 

	// is there a collision? true or false? easy


    if( ((vector.x*point.x) + (vector.y*point.y) + (vector.z*point.z) + D) <= 0)
		return true;
	return false;
}