!round_grid  /modified 2/16/94***VL/
!internal macro: -
!dx=a,dy=b,z=grid width,d=frame thickness

addy b/2

let i=a/2
let j=b/2
let k=c
let l=0.5*i-k
let m=(j/i)*sqr(i*i-l*l)
let n=0.5*j+k
let o=(i/j)*sqr(j*j-n*n)

if (i*i-l*l)<0 then 20

prism_ 4, d/6,
0.5*i,0.866*j,8,
l,m,15,
l,-m,8,
0.5*i,-0.866*j,15

prism_ 4, d/6,
0.866*i,0.5*j,8,
o,n,15,
-o,n,8,
-0.866*i,0.5*j,15


mulx -1

prism_ 4, d/6,
0.5*i,0.866*j,8,
l,m,15,
l,-m,8,
0.5*i,-0.866*j,15

muly -1

prism_ 4,d/6,
0.866*i,0.5*j,8,
o,n,15,
-o,n,8,
-0.866*i,0.5*j,15

20:del top
end
