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- §

  # Demo Particles 009

  Net particles: drag-and-drop; collisions

- §

  Run code

      import * as scrawl from '../source/scrawl.js'

      import { reportSpeed } from './utilities.js';

- §

  #### Scene setup

      const canvas = scrawl.library.artefact.mycanvas;

- §

  Define some filters

      scrawl.makeFilter({
          name: 'grayscale',
          method: 'grayscale',
      }).clone({
          name: 'invert',
          method: 'invert',
      });

      scrawl.makeFilter({
          name: 'tint',
          method: 'tint',
          redInRed: 0.5,      redInGreen: 1,      redInBlue: 0.9,
          greenInRed: 0,      greenInGreen: 0.3,  greenInBlue: 0.8,
          blueInRed: 0.8,     blueInGreen: 0.8,   blueInBlue: 0.4,
      });

      scrawl.makeFilter({
          name: 'matrix',
          method: 'matrix',
          weights: [-1, -1, 0, -1, 1, 1, 0, 1, 1],
      });

- §

  For this Demo, we are creating a sheet and pinning its top row to a rail. This is the rail.

      scrawl.makeLine({

          name: 'topline',

          startX: '10%',
          startY: '5%',
          endX: '90%',
          endY: '5%',

          lineWidth: 20,
          lineCap: 'round',
          strokeStyle: 'brown',

          method: 'draw',
      });

- §

  #### Particle physics animation scene

- §

  Create a repeller force, associated with a Wheel entity

      const bigball = scrawl.makeWheel({

          name: 'big-ball',
          radius: 80,
          handle: ['center', 'center'],
          start: ['center', 320],

          fillStyle: 'coral',
          strokeStyle: 'orange',
          lineWidth: 3,
          method: 'fillThenDraw',

- §

  Default action is for a dragged entity to attempt to place itself over all other entitys (in its Group). We can prevent this by setting the `bringToFrontOnDrag` to `false`

          bringToFrontOnDrag: false,
      });

- §

  The repeller force

      scrawl.makeForce({

          name: 'wheel-repellor',
      /* eslint-disable-next-line */
          action: (particle, world, host) => {

              const {load, position} = particle;

              const ballPosition = bigball.get('position');

- §

  We are using Scrawl-canvas Pool vectors for this calculation, which we need to request before we can use them.

              const v = scrawl.requestVector(ballPosition).vectorSubtract(position);

              const mag = v.getMagnitude();

              if (mag && mag < bigball.get('radius')) {

                  v.scalarMultiply(1 / (mag / 1000));
                  load.vectorSubtract(v)
              }

- §

  When we are finished with the vector, we MUST release it back to the pool!

              scrawl.releaseVector(v);
          },
      });

- §

  Create a World object which we can then assign to the Net entity

      const myWorld = scrawl.makeWorld({

          name: 'demo-world',
          tickMultiplier: 2,

      });

- §

  Create the Net entity

      const myNet = scrawl.makeNet({

          name: 'test-net',
          world: myWorld,

          pivot: 'topline',
          lockTo: 'pivot',

          generate: 'weak-net',

          postGenerate: function () {

- §

  We want to make all of the top row Particles visually different, and static

              const regex = RegExp('-0-[0-9]+$');

- §

  @ts-expect-error

              this.particleStore.forEach(p => {

                  if (regex.test(p.name)) {

                      p.set({
                          fill: 'lightgrey',
                          stroke: 'red',
                          forces: [],
                      });

- §

  @ts-expect-error

                      this.springs.forEach(s => {

                          if (s && s.particleFrom && s.particleFrom.name === p.name) {

                              s.particleFromIsStatic = true;
                          }
                          if (s && s.particleTo && s.particleTo.name === p.name) {

                              s.particleToIsStatic = true;
                          }
                      })
                  }
              });
          },

          rows: 15,
          columns: 17,
          rowDistance: 25,
          columnDistance: 30,
          showSprings: true,
          showSpringsColor: 'azure',

          forces: ['gravity', 'wheel-repellor'],

          mass: 3,
          springConstant: 100,

          engine: 'runge-kutta',

          artefact: scrawl.makeWheel({

              name: 'particle-wheel',
              radius: 7,

              handle: ['center', 'center'],

              method: 'fillThenDraw',
              fillStyle: 'yellow',
              strokeStyle: 'gold',

              visibility: false,

              noUserInteraction: true,
              noPositionDependencies: true,
              noFilters: true,
              noDeltaUpdates: true,
          }),

          stampAction: function (artefact, particle, host) {

              const [ , , ...start] = particle.history[0];

              artefact.simpleStamp(host, {
                  start,
                  fillStyle: particle.fill,
                  strokeStyle: particle.stroke,
              });
          },

- §

  Make all of the Net entity’s Particles draggable

          particlesAreDraggable: true,
      });

- §

  #### Scene animation

  Function to display frames-per-second data, and other information relevant to the demo

      const report = reportSpeed('#reportmessage');

- §

  Create the Display cycle animation

      scrawl.makeRender({

          name: 'demo-animation',
          target: canvas,
          afterShow: report,
      });

- §

  #### User interaction

  Make both the Net entity’s Particles, and the big ball, draggable

  - KNOWN BUG - the entitys/particles are not draggable on first user mousedown, but are draggable afterwards

      scrawl.makeGroup({

          name: 'my-draggable-group',

      }).addArtefacts('test-net', 'big-ball');

      scrawl.makeDragZone({

          zone: canvas,
          collisionGroup: 'my-draggable-group',
          endOn: ['up', 'leave'],
          preventTouchDefaultWhenDragging: true,
      });

- §

  When we set a filter on a Net entity, all the entity’s visual output will be filtered

      const filterChoice = function (e) {

          e.preventDefault();
          e.returnValue = false;

          const val = e.target.value;

          myNet.clearFilters();
          if (val) myNet.addFilters(val);
      };
      scrawl.addNativeListener(['input', 'change'], filterChoice, '#filter');

- §

  Set DOM form initial input values @ts-expect-error

      document.querySelector('#filter').value = '';

- §

  #### Development and testing

      console.log(scrawl.library);