iso3.py

# Nicolas Seriot
# 2021-09-16
# Thread: https://twitter.com/nst021/status/1437889678947110912
# Typical output: https://seriot.ch/visualization/iso3.png

import cairo
import random
import numpy as np

MARGIN = 50
X_MAX, Y_MAX, Z_MAX = 12, 16, 5 # space size
DW, DH = 60, 30 # diamond size
DW2, DH2 = int(DW/2), int(DH/2)
N = 300

def draw_surface(c, points, color):

    c.save()

    c.set_source_rgb(*color)
    c.set_line_width(1)
    
    [c.line_to(*p) for p in points]

    c.close_path()
    c.fill_preserve()
    c.set_source_rgb(0,0,0)

    c.set_line_join(cairo.LINE_CAP_SQUARE) # ok aa
    c.stroke()

    c.restore()

def draw_grid(c):

    for x in range(X_MAX):
        for y in range(Y_MAX):
            draw_cube(c, x, y, 0, flat=True)

def model_to_canvas(x, y):

    o_x = DW2 * Y_MAX
    o_y = DH2
    
    return (o_x + DW2*(x-y), o_y + DH2*(x+y))

def draw_cube(c, x, y, z, flat=False):
    
    print("--", x, y, z)
    
    x, y = model_to_canvas(x, y)
    
    c.save()

    c.translate(x, y)

    """
      5
    2   6
      3      - DH
    1   7
      4
      | z_offset
    """
    
    z_offset = DH * z

    p1 = (0,   z_offset + DH2)
    p2 = (0,   z_offset + DH2 + DH)
    p3 = (DW2, z_offset + DH)
    p4 = (DW2, z_offset + 0)
    p5 = (DW2, z_offset + 2*DH)
    p6 = (DW,  z_offset + DH2 + DH)
    p7 = (DW,  z_offset + DH2)
    
    #COLOR_RIGHT = (0.5,0.5,0.5)
    #COLOR_TOP = (1,1,1)
    #COLOR_LEFT = (0,0,0)
    
    z_ratio = 0.4 + z*0.6/Z_MAX
    
    COLOR_TOP   = (1 * z_ratio,   0.5 * z_ratio, 0.5 * z_ratio)
    COLOR_LEFT  = (0.6 * z_ratio, 0,   0)
    COLOR_RIGHT = (1 * z_ratio,   0,   0)
    
    if flat:
        draw_surface(c, [p1, p3, p7, p4], (1,1,1))
    else:
        draw_surface(c, [p2, p5, p6, p3], COLOR_TOP)
        draw_surface(c, [p1, p2, p3, p4], COLOR_LEFT)
        draw_surface(c, [p3, p6, p7, p4], COLOR_RIGHT)
    
    c.restore()

def fill_model(m):

    for _ in range(N):
        x = random.randint(0, X_MAX-1)
        y = random.randint(0, Y_MAX-1)
        z = random.randint(0, Z_MAX-1)

        m[x][y][z] = True

def draw_model(c, m):
    
    X,Y,Z = m.shape

    for x in range(X)[::-1]:
        for y in range(Y)[::-1]:
            for z in range(Z_MAX):
                if m[x][y][z]:
                    draw_cube(c,x,y,z)

m = np.full((X_MAX, Y_MAX, Z_MAX), False, dtype=bool)

fill_model(m)

#m[2][3][0] = True
#m[2][3][1] = True
#m[3][3][0] = True

surface = cairo.ImageSurface(cairo.FORMAT_ARGB32,
                             DW + (X_MAX+Y_MAX)*DW2 + MARGIN*2,
                             DH + (X_MAX+Y_MAX)*DH2 + Z_MAX*DH + MARGIN*2)
c = cairo.Context(surface)

cm = cairo.Matrix(yy=-1, y0=surface.get_height())
c.transform(cm)

c.translate(MARGIN, MARGIN)

c.set_antialias(cairo.ANTIALIAS_NONE)

#background
c.set_source_rgb(1,1,1)
c.paint()

#pen
c.set_source_rgb(0,0,0)
c.set_line_width(1)

draw_grid(c)
draw_model(c, m)

#draw_cube(c, 1, 0, 0)

surface.write_to_png("iso3.png")