NB. cups surface - colored by height

j=. steps _2.4 2.4 35
f=. (5: * ] % ^@+&*:)"0/~
CUPS=: 1.4*fit11 makexyz (];];f) j

j=. (1r4"_ ,. |. ,. ]) _2}.8}. int01 16
CUPCLR=: j hue fit01 {:"1 CUPS

ROTXYZ=: 285 0 335
CLEARCOLOR=: IVORY

demo=: 3 : 0
stdlistlight''
2 drawsurface makenewlist CUPS;CUPCLR
)

demo''
