G=ContourPlot3D[Cos[x] Sin[y]+Cos[y] Sin[z]+Cos[z] Sin[x]==0,{x,0,2 Pi},{y,0,2 Pi},{z,0,2 Pi},PlotPoints->3]

G=ContourPlot3D[Cos[x] +Cos[y] +Cos[z] ==0,{x,0,2 Pi},{y,0,2 Pi},{z,0,2 Pi}]