graph3d((((x*(a^2 - b^2 - c^2) + 2*a*(b*y + c*z + d))/(a^2 + b^2 + c^2))^2 + (- (2*a*b*x - y*(a^2 - b^2 + c^2) + 2*b*(c*z + d))/(a^2 + b^2 + c^2))^2 + (- (2*a*c*x + 2*b*c*y - z*(a^2 + b^2 - c^2) + 2*c*d)/(a^2 + b^2 + c^2))^2 = 0.5,x^2+y^2+z^2=0.5,a*x+b*y+c*z+d=0))