The G (Gyroid) Surface is a triply periodic minimal surface discovered in late 1960s by Alan Schoen. This is its equation in Mathematica 7:

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]

I did the following G model using K3DSurf, GEM and Maya. Many thanks to the ParaCloud team for their great support!