dna_scene.dart

/// copyright roipeker 2020
///
/// web demo:
/// https://roi-graphx-spiral3d.surge.sh
/// 

import 'package:flutter/material.dart';
import 'package:graphx/graphx.dart';

main() {
  runApp(MaterialApp(
    home: SceneBuilderWidget(
      builder: () => SceneController(back: DnaScene()),
    ),
  ));
}

class DnaScene extends Sprite {
  double spiralRadius, centerX, centerY, centerZ;
  double fl = 150;

  List<Dot> dots;

  @override
  void addedToStage() async {
    stage.color = Colors.white.value;
    dots = List.generate(80, (index) {
      var dot = Dot();
      addChild(dot);
      dot.py = -200.0 + index * 5.0;
      dot.angle = index * 20.0;
      return dot;
    });
  }

  @override
  void update(t) {
    centerX = stage.stageWidth / 2;
    centerY = stage.stageHeight / 2;
    centerZ = 100.0;

    spiralRadius = (mouseX - centerX) / 4;

    dots.forEach((dot) {
      double dotAngle = deg2rad(dot.angle);
      var pz = sin(dotAngle) * spiralRadius + centerZ;
      var fov = fl / (fl + pz);

      /// calculate `px` position only, `py` is predefined in the
      /// initialization.
      var px = cos(dotAngle) * spiralRadius;
      dot.x = px * fov + centerX;
      dot.y = dot.py * fov + centerY;
      dot.alpha = dot.scale = fov;

      dot.updateAngle();
    });
  }
}

/// we just make a class to store the basic properties
/// for the calculations.
class Dot extends Shape {
  double py, angle, speed = 5;
  Dot() {
    graphics.beginFill(0x0).drawCircle(0, 0, 10).endFill();
  }
  void updateAngle() {
    angle += speed;
    if (angle >= 360) {
      angle -= 360;
    }
  }
}