vector3d.h

#ifndef VECTOR3D__H
#define VECTOR3D__H

//get modulus of a 3d vector sqrt(x^2+y^2+y^2)
float vector3d_modulus(float* vector){
	static float R;  
	R = vector[0]*vector[0];
	R += vector[1]*vector[1];
	R += vector[2]*vector[2];
	return sqrt(R);
}

//convert vector to a vector with same direction and modulus 1
void vector3d_normalize(float* vector){
	static float R;  
	R = vector3d_modulus(vector);
	vector[0] /= R;
	vector[1] /= R; 
	vector[2] /= R;  
}

//calcuate vector dot-product  c = a . b
float vector3d_dot(float* a,float* b){
	return a[0]*b[0]+a[1]*b[1]+a[2]*b[2];
}


//calcuate vector cross-product  c = a x b
void vector3d_cross(float* a,float* b, float* c){
	c[0] = a[1]*b[2] - a[2]*b[1];
	c[1] = a[2]*b[0] - a[0]*b[2];
	c[2] = a[0]*b[1] - a[1]*b[0];
}

//calcuate vector scalar-product  n = s x a
void vector3d_scale(float s, float* a , float* b){
	b[0] = s*a[0];
	b[1] = s*a[1];
	b[2] = s*a[2];
} 


//calcuate vector sum   c = a + b
void vector3d_add(float* a , float* b, float* c){
	c[0] = a[0] + b[0];
	c[1] = a[1] + b[1];
	c[2] = a[2] + b[2];
} 


//creates equivalent skew symetric matrix plus identity
//for v = {x,y,z} returns
// m = {{1,-z,y}
//		{z,1,-x}
//		{-y,x,1}}
void vector3d_skew_plus_identity(float *v,float* m){
	m[0*3+0]=1;
	m[0*3+1]=-v[2];
	m[0*3+2]=v[1];
	m[1*3+0]=v[2];
	m[1*3+1]=1;
	m[1*3+2]=-v[0];
	m[2*3+0]=-v[1];
	m[2*3+1]=v[0];
	m[2*3+2]=1;
}





#endif