void translate_xyz(float* result, const float translatex,
		const float translatey, const float translatez) {
	result[12] += result[0] * translatex + result[4] * translatey
			+ result[8] * translatez;
	result[13] += result[1] * translatex + result[5] * translatey
			+ result[9] * translatez;
	result[14] += result[2] * translatex + result[6] * translatey
			+ result[10] * translatez;
	result[15] += result[3] * translatex + result[7] * translatey
			+ result[11] * translatez;
}

float length(const float x, const float y, const float z) {
	return (float) sqrt(x*x + y*y +z*z);
}

void view_set_lookat(float* result,
		const float eyex, const float eyey, const float eyez,
		const float centerx, const float centery, const float centerz,
		const float upx, const float upy, const float upz) {

	float fx = centerx - eyex;
	float fy = centery - eyey;
	float fz = centerz - eyez;

	// normalize f
	float rlf = 1.0f / length(fx, fy, fz);
	fx *= rlf;
	fy *= rlf;
	fz *= rlf;

	// compute s = f x up (x means "cross product")
    float sx = fy * upz - fz * upy;
    float sy = fz * upx - fx * upz;
    float sz = fx * upy - fy * upx;

    // and normalize s
    float rls = 1.0f / length(sx, sy, sz);
    sx *= rls;
    sy *= rls;
    sz *= rls;

    //The up vector must not be parallel to the line of sight from the eye point to the reference point.
    if((0 == sx)&&(0 == sy)&&(0 == sz))
    	return;
    	
    // compute u = s x f
    float ux = sy * fz - sz * fy;
    float uy = sz * fx - sx * fz;
    float uz = sx * fy - sy * fx;

    result[0] = sx;
    result[1] = ux;
    result[2] = -fx;
    result[3] = 0.0f;

    result[4] = sy;
    result[5] = uy;
    result[6] = -fy;
    result[7] = 0.0f;

    result[8] = sz;
    result[9] = uz;
    result[10] = -fz;
    result[11] = 0.0f;

    result[12] = 0.0f;
    result[13] = 0.0f;
    result[14] = 0.0f;
    result[15] = 1.0f;

    translate_xyz(result, -eyex, -eyey, -eyez);
}