Question: animation of a function f(x,y,t)

hi,

 

i ve to animate a function with maple. but my animation "vanishes" after some time so i wonder what i did wrong

my function f (x,y,t) = sin(sqrt(x^2+y^2-t))/sqrt(x^2+y^2-1)

this is how i tried it:

f := (x,y,t)->(sin(sqrt(x^2+y^2-t))/(sqrt(x^2+y^2+1)));
plots:-animate(plot3d, [f(x,y,t), x=-10..10,y=-10..10], t=-100..190);
 

if you let the animation run the animation starts to vanish, what am i doing wrong

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