[Closed] rendermap return black only

Hello all , I’m try to render texmap [cellular], but it always return black, but when using rendermap from medit- util , it return just fine, could someone pointing the right way? this is the code…

cell = cellularTex() 
cell.size=50 
cell.spread=0.3 
cell.fractal=on 
rendermap cell size:[500,500] filter:on display:on