Fractal Tree Tutorial

Start with a Tree Trunk

Firstoff, include the BOSL2 library, then make a starting module that just has a tapered cylinder for the tree trunk.

include <BOSL2/std.scad>
module tree(l=1500, sc=0.7)
    cylinder(h=l, d1=l/5, d2=l/5*sc);
tree();

Attaching a Branch

You can attach a branch to the top of the trunk by using attach() as a child of the trunk cylinder.

include <BOSL2/std.scad>
module tree(l=1500, sc=0.7)
    cylinder(h=l, d1=l/5, d2=l/5*sc)
        attach(TOP)
            yrot(30) cylinder(h=l*sc, d1=l/5*sc, d2=l/5*sc*sc);
tree();

Replicating the Branch

Instead of attaching each branch individually, you can make multiple copies of one branch, that are rotated relative to each other.

include <BOSL2/std.scad>
module tree(l=1500, sc=0.7)
    cylinder(h=l, d1=l/5, d2=l/5*sc)
        attach(TOP)
            zrot_copies(n=2)  // Replicate that branch
                yrot(30) cylinder(h=l*sc, d1=l/5*sc, d2=l/5*sc*sc);
tree();

Use Recursion

Since branches look much like the main trunk, we can make the tree recursive. Don't forget the termination clause, or else it'll try to recurse forever!

include <BOSL2/std.scad>
module tree(l=1500, sc=0.7, depth=10)
    cylinder(h=l, d1=l/5, d2=l/5*sc)
        attach(TOP)
            if (depth>0)  { // Important!
                zrot_copies(n=2)
                yrot(30) tree(depth=depth-1, l=l*sc, sc=sc);
            }
tree();

Make it Not Flat

A flat planar tree isn't what we want, so lets bush it out a bit by rotating each level 90 degrees.

include <BOSL2/std.scad>
module tree(l=1500, sc=0.7, depth=10)
    cylinder(h=l, d1=l/5, d2=l/5*sc)
        attach(TOP)
            if (depth>0) {
                zrot(90)  // Bush it out
                zrot_copies(n=2)
                yrot(30) tree(depth=depth-1, l=l*sc, sc=sc);
            }
tree();

Adding Leaves

Let's add leaves. They look much like squashed versions of the standard teardrop() module, so lets use that.

include <BOSL2/std.scad>
module tree(l=1500, sc=0.7, depth=10)
    cylinder(h=l, d1=l/5, d2=l/5*sc)
        attach(TOP)
            if (depth>0) {
                zrot(90)
                zrot_copies(n=2)
                yrot(30) tree(depth=depth-1, l=l*sc, sc=sc);
            } else {
                yscale(0.67)
                teardrop(d=l*3, l=1, anchor=BOT, spin=90);
            }
tree();

Adding Color

We can finish this off with some color. The color() module will force all it's children and their descendants to the new color, even if they were colored before. The recolor() module, however, will only color children and decendants that don't already have a color set by a more nested recolor().

include <BOSL2/std.scad>
module tree(l=1500, sc=0.7, depth=10)
    recolor("lightgray")
    cylinder(h=l, d1=l/5, d2=l/5*sc)
        attach(TOP)
            if (depth>0) {
                zrot(90)
                zrot_copies(n=2)
                yrot(30) tree(depth=depth-1, l=l*sc, sc=sc);
            } else {
                recolor("springgreen")
                yscale(0.67)
                teardrop(d=l*3, l=1, anchor=BOT, spin=90);
            }
tree();

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