Animation of a 3D graph : animate3d

animate3d can create a 3-d animation with function graphs depending of a parameter. The parameter is specified as the third argument of animate3d, the number of pictures as fourth argument with frames=number, the remaining arguments are the same as those of the plotfunc command, see section 2.2.2, p. .
Input :

animate3d(x^2+a*y^2,[x=-2..2,y=-2..2],a=-2..2, frames=10,display=red+filled)

Output :

a sequence of graphic representations of z=x^2+a*y^2 for 11 values of a between -2 and 2