setscreen ("offscreenonly,graphics:1000;700,nobuttonbar,position:middle;middle")

type _3D :
    record
        x : real
        y : real
        z : real
    end record

const xs := 30
const zs := 30
const perspective := 400
const spread := 10
const amplitude := 12
const wavelength := 2

var coords : array 1 .. xs * zs of _3D
var depth : int
var n : int := 0
var x, y, oldx, oldy : int
var angX, angY : real := 45
var a : real := 0

const colors := 220
var clr : array - colors div 2 .. colors div 2 of int
for i : 1 .. colors
    clr (i - colors div 2) := RGB.AddColor (i / colors, i / colors, i / colors)
end for

var COS, SIN : array 0 .. 360 of real
for i : 0 .. 360
    COS (i) := cos (i * (Math.PI / 180))
    SIN (i) := sin (i * (Math.PI / 180))
end for

procedure rotate (xpp, ypp, zpp, ax, ay, az : real)
    var temp : real
    var xp, yp, zp : real
    yp := ypp * COS (round (ax)) - zpp * SIN (round (ax))
    zp := zpp * COS (round (ax)) + ypp * SIN (round (ax))
    temp := zp
    zp := zp * COS (round (ay)) - xpp * SIN (round (ay))
    xp := xpp * COS (round (ay)) + temp * SIN (round (ay))
    temp := xp
    xp := xp * COS (round (az)) - yp * SIN (round (az))
    yp := yp * COS (round (az)) + temp * SIN (round (az))
    depth := round (zp)
    x := round (xp / (1 - zp / perspective)) + maxx div 2
    y := round (yp / (1 - zp / perspective)) + maxy div 2
end rotate

for _x : 1 .. xs
    for _z : 1 .. zs
        n += 1
        coords (n).x := _x * spread - (xs / 2) * spread
        coords (n).z := _z * spread - (zs / 2) * spread
        coords (n).y := (cos (_x / wavelength) * amplitude) + (sin (_z / wavelength) * amplitude)
    end for
end for

loop
    n := 0
    a += 0.05
    angX := sin (a) * 35 + 90
    angY += 2
    for _x : 1 .. xs
        for _z : 1 .. zs
            n += 1
            rotate (coords (n).x, coords (n).y, coords (n).z, angX mod 360, 1, angY mod 360)
            if _z > 1 then
                Draw.ThickLine (oldx, oldy, x, y, (depth + 250) div 15, clr (depth * -1))
            end if
            oldx := x
            oldy := y
        end for
    end for
    View.Update
    cls
end loop