dotSCAD/docs/lib3x-contours.md

contours

Computes contour polygons by applying marching squares to a rectangular list of numeric values.

Since: 2.3

Parameters

• points : A list of points [x, y, z]. See examples below.
• threshold : When applying a threshold value, the function returns isolines. When applying upper and lower threshold values, it returns isobands.

Examples

use <hull_polyline2d.scad>;
use <surface/sf_thicken.scad>;
use <contours.scad>;

min_value =  1;
max_value = 360;
resolution = 10;

function f(x, y) = sin(x) * cos(y) * 30;

points = [
    for(y = [min_value:resolution:max_value])
        [
            for(x = [min_value:resolution:max_value]) 
                [x, y, f(x, y)]
        ]
];

sf_thicken(points, 1);

translate([max_value, 0, 0]) 
for(z = [-30:5:30]) {
    translate([0, 0, z])
    linear_extrude(1)
    for(isoline = contours(points, z)) {
        hull_polyline2d(isoline, width = 1);
    }    
}

translate([0, max_value]) 
for(z = [-30:5:30]) {
    linear_extrude(35 + z)
    for(isoband = contours(points, [z, z + 5])) {
        polygon([for(p = isoband) [p[0], p[1]]]);
    } 
}