
Intertwining based on the geometry of the Boy surface [Entrelacs basé sur la géométrie de la surface de Boy].
= MountainEffect(TapestryEffect(PA[FX[x,y],FY[x,y]]))
FX[x,y] = A11.PX[x,y] + A12.PY[x,y] + A13.PZ[x,y]
FY[x,y] = A21.PX[x,y] + A22.PY[x,y] + A23.PZ[x,y]
(the 'X' pseudo-projection of the Boy surface)
(the 'Y' pseudo-projection of the Boy surface)
(the 'Z' pseudo-projection of the Boy surface)