### Delegated deferred polygons ðŸ”º

I'm revisiting a turtle by @reinder
Polygon hatching

I modified the code to work with my delegated hatching and deferred drawing extensions.

#polygons #Escher

```// Forked from "Polygon hatching" by reinder
// https://turtletoy.net/turtle/92ebe08d89

// Polygon delegated hatching and deferred drawing. Created by Jurgen Westerhof 2024
//
// https://turtletoy.net/turtle/d1095a7e5d
//
// Original:
//
// Polygon hatching. Created by Reinder Nijhoff 2018
// @reindernijhoff
//
// https://turtletoy.net/turtle/92ebe08d89
//
// You can find the Turtle API reference here: https://turtletoy.net/syntax
Canvas.setpenopacity(.6);

// Global code will be evaluated once.
const turtle = new Turtle();
const polygons = new Polygons();
polygons.startDeferSession();

const hatchings = Array.from({length: 3}).map((e,i) => new LineHatching((i-1/3)*Math.PI/2, .3+i*.5, .3));

function walk(i) {
const s = 25;
const sp = 12.5;

// first an invisible cube is added to the clip list.
//if (i ==0) drawCube((3-8/2)*(s+sp),2*s-(s+sp)*(-8+9)/Math.sqrt(1.25),s,0,false);

if (i < 4)  drawCube((i-1.5)*(s+sp),2*s,s);
else if (i < 7)  drawCube((3-i/2)*(s+sp),2*s-(s+sp)*(i-3)/Math.sqrt(1.25),s);
else if (i < 9)  drawCube((3-i/2)*(s+sp),2*s-(s+sp)*(-i+9)/Math.sqrt(1.25),s);//,9);

if(i == 2) {
polygons.stopDeferring();
} else if(i == 9) {
polygons.finalizeDeferSession(turtle);
}
return i < 9;
}

function drawCube(x,y,r) { //,skip=0,draw=true) {
const p = [[x,y]];
for (let i=0; i<6; i++) {
p.push([Math.cos(i*Math.PI/3)*r+x, Math.sin(i*Math.PI/3)*r+y]);
}
// create 3 visible polygons for cube
const ps = [];
for (let i=0; i<3; i++) {
const c = polygons.create();
polygons.draw(turtle, c);
}
}

///////////////////////////////////////////////////////////////////
// This is only the part of the Polygon Hatching utility code
// required in this turtle. For the full hatchery code see
//
///////////////////////////////////////////////////////////////////
// Polygon Hatching utility code - Created by Jurgen Westerhof 2024
// ////////////////////////////////////////////////////////////////
// // To be used with modified Polygon Clipping utility code
// //            Orginal: https://turtletoy.net/turtle/a5befa1f8d
// //    Polygon binning: https://turtletoy.net/turtle/95f33bd383
///////////////////////////////////////////////////////////////////
//for convenience on Turtletoy you can click the arrow to the right of the line number to collapse a class
//////////////////////////////////////////////////// root
class PolygonHatching {
constructor() {
if (this.constructor === PolygonHatching) {
throw new Error("PolygonHatching is an abstract class and can't be instantiated.");
}

this.minX = -100;
this.minY = -100;
this.maxX = 100;
this.maxY = 100;
this.width = 200;
this.height = 200;

this.segments = [];

this.init();
}
hatch(polygonsClass, thePolygonToHatch) {
const e = new polygonsClass;
e.cp.push(...thePolygonToHatch.aabb);//[-1e5,-1e5],[1e5,-1e5],[1e5,1e5],[-1e5,1e5]);

e.boolean(thePolygonToHatch,!1);
thePolygonToHatch.dp=[...thePolygonToHatch.dp,...e.dp]
}
this.getSegments().forEach(e => segments.push(e));
}
getSegments() { return this.segments; }
init() {
///////////////////////////////////////////////////////
// Vector functions - Created by Jurgen Westerhof 2024
///////////////////////////////////////////////////////
class Vector {
static add  (a,b) { return a.map((v,i)=>v+b[i]); }
static sub  (a,b) { return a.map((v,i)=>v-b[i]); }
static mul  (a,b) { return a.map((v,i)=>v*b[i]); }
static div  (a,b) { return a.map((v,i)=>v/b[i]); }
static scale(a,s) { return a.map(v=>v*s); }

static det(m)                { return m.length == 1? m[0][0]: m.length == 2 ? m[0][0]*m[1][1]-m[0][1]*m[1][0]: m[0].reduce((r,e,i) => r+(-1)**(i+2)*e*this.det(m.slice(1).map(c => c.filter((_,j) => i != j))),0); }
static angle(a)              { return Math.PI - Math.atan2(a[1], -a[0]); } //compatible with turtletoy heading
static rot2d(angle)          { return [[Math.cos(angle), -Math.sin(angle)], [Math.sin(angle), Math.cos(angle)]]; }
static rot3d(yaw,pitch,roll) { return [[Math.cos(yaw)*Math.cos(pitch), Math.cos(yaw)*Math.sin(pitch)*Math.sin(roll)-Math.sin(yaw)*Math.cos(roll), Math.cos(yaw)*Math.sin(pitch)*Math.cos(roll)+Math.sin(yaw)*Math.sin(roll)],[Math.sin(yaw)*Math.cos(pitch), Math.sin(yaw)*Math.sin(pitch)*Math.sin(roll)+Math.cos(yaw)*Math.cos(roll), Math.sin(yaw)*Math.sin(pitch)*Math.cos(roll)-Math.cos(yaw)*Math.sin(roll)],[-Math.sin(pitch), Math.cos(pitch)*Math.sin(roll), Math.cos(pitch)*Math.cos(roll)]]; }
static trans(matrix,a)       { return a.map((v,i) => a.reduce((acc, cur, ci) => acc + cur * matrix[ci][i], 0)); }
//Mirror vector a in a ray through [0,0] with direction mirror
static mirror2d(a,mirror)    { return [Math.atan2(...mirror)].map(angle => this.trans(this.rot2d(angle), this.mul([-1,1], this.trans(this.rot2d(-angle), a)))).pop(); }

static approx(a,b,p) { return this.len(this.sub(a,b)) < (p === undefined? .001: p); }
static norm  (a)     { return this.scale(a,1/this.len(a)); }
static len   (a)     { return Math.hypot(...a); }
static lenSq (a)     { return a.reduce((a,c)=>a+c**2,0); }
static lerp  (a,b,t) { return a.map((v, i) => v*(1-t) + b[i]*t); }
static dist  (a,b)   { return Math.hypot(...this.sub(a,b)); }

static dot  (a,b)   { return a.reduce((a,c,i) => a+c*b[i], 0); }
static cross(...ab) { return ab[0].map((e, i) => ab.map(v => v.filter((ee, ii) => ii != i))).map((m,i) => (i%2==0?-1:1)*this.det(m)); }
}
this.V = Vector;

class Intersection2D {
//a-start, a-direction, b-start, b-direction
//returns false on no intersection or [[intersection:x,y], scalar a-direction, scalar b-direction
static info(as, ad, bs, bd) {
const d = V.sub(bs, as), det = -V.det([bd, ad]);
if(det === 0) return false;
const res = [V.det([d, bd]) / det, V.det([d, ad]) / det];
}
static ray(a, b, c, d) {
return this.info(a, b, c, d);
}
static segment(a,b,c,d, inclusiveStart = true, inclusiveEnd = true) {
const i = this.info(a, V.sub(b, a), c, V.sub(d, c));
return i === false? false: (
(inclusiveStart? 0<=i[1] && 0<=i[2]: 0<i[1] && 0<i[2])
&& (inclusiveEnd?   i[1]<=1 && i[2]<=1: i[1]<1 && i[2]<1)
)?i[0]:false;
}
}
this.Intersection = Intersection2D;
}
}
this.PolygonHatching = PolygonHatching;
class LineHatching extends PolygonHatching {
constructor(angle, distance, inp = 0) {
super();

const h=Math.sin(angle)*distance,o=Math.cos(angle)*distance,a=200*Math.sin(angle),i=200*Math.cos(angle);
this.segments = Array.from({length: 150/distance}).flatMap((x,y,z,t=.5+y) => [
[h*t+i+inp*(Math.random()-.5),o*t-a+inp*(Math.random()-.5)],[h*t-i+inp*(Math.random()-.5),o*t+a+inp*(Math.random()-.5)], [-h*t+i+inp*(Math.random()-.5),-o*t-a+inp*(Math.random()-.5)],[-h*t-i+inp*(Math.random()-.5),-o*t+a+inp*(Math.random()-.5)]
])
}
}
this.LineHatching = LineHatching;
}

////////////////////////////////////////////////////////////////
// Polygon Clipping utility code - Created by Reinder Nijhoff 2019
// (Polygon binning by Lionel Lemarie 2021) https://turtletoy.net/turtle/95f33bd383
// (Delegated Hatching by Jurgen Westerhof 2024) https://turtletoy.net/turtle/d068ad6040
// (Deferred Polygon Drawing by Jurgen Westerhof 2024) https://turtletoy.net/turtle/6f3d2bc0b5
// https://turtletoy.net/turtle/a5befa1f8d
//
// const polygons = new Polygons();
// const p = polygons.create();
// polygons.draw(turtle, p);
// polygons.list();
// polygons.startDeferSession();
// polygons.stopDeferring();
// polygons.finalizeDeferSession(turtle);
//