icosphere.pde

   PShape createSphere(float r, int detail) {
        PShape res = createShape();
        float deg5 = TWO_PI / 5f;
        float deg6 = acos((1f + sqrt(5f)) / (5f + sqrt(5f)));
        PVector top = new PVector(0, r, 0);
        PVector[] sides = new PVector[5];
        for (int i = 0; i < 5; i++) {
            sides[i] = new PVector(
                    r * sin(deg6) * cos(deg5 * i),
                    r * cos(deg6),
                    r * sin(deg6) * sin(deg5 * i));
        }
        res.disableStyle();
        res.beginShape(TRIANGLES);
        for (int i = 0; i < 5; i++) {
            trig(res, r, top, sides[(i + 1) % 5], sides[i], detail);
            trig(res, r, sides[i], flip(sides[(i + 3) % 5]), flip(sides[(i + 2) % 5]), detail);
            trig(res, r, flip(sides[i]), sides[(i + 2) % 5], sides[(i + 3) % 5], detail);
            trig(res, r, flip(top), flip(sides[i]), flip(sides[(i + 1) % 5]), detail);
        }
        res.endShape();
        return res;
    }

    PVector flip(PVector v) {
        return new PVector(-v.x, -v.y, -v.z);
    }

    void trig(PShape ps, float r, PVector p1, PVector p2, PVector p3, int detail) {
        if (detail > 1) {
            PVector mid12 = PVector.add(p1, p2);
            mid12.setMag(r);
            PVector mid23 = PVector.add(p2, p3);
            mid23.setMag(r);
            PVector mid13 = PVector.add(p1, p3);
            mid13.setMag(r);
            detail--;
            trig(ps, r, p1, mid12, mid13, detail);
            trig(ps, r, p2, mid23, mid12, detail);
            trig(ps, r, p3, mid13, mid23, detail);
            trig(ps, r, mid12, mid23, mid13, detail);
        } else {
            PVector dir = PVector.add(p1, p2);
            dir.add(p3);
            normal(ps, dir);
            vertex(ps, p1);
            vertex(ps, p2);
            vertex(ps, p3);
        }
    }

    void vertex(PShape ps, PVector v) {
        ps.vertex(v.x, v.y, v.z);
    }

    void normal(PShape ps, PVector v) {
        ps.normal(v.x, v.y, v.z);
    }