计算机图形学&Web前端笔记-浏览器中心点转场景坐标理论及实现（two.js）

实现的功能是这样的：

输入window.mainPage.flyTo(xxx, xxx)

后会在浏览器中心点画个圆心，使用鼠标及滚轮滚动后。

再次运行：

前一篇博文已经说了3*3变化矩阵实现图形放缩及平移，这里不再多谈，此处只记录下，将屏幕中心点坐标，转换为two.js的场景坐标点：

这里的two.scene._matrix就是3*3的矩阵。

cirX = （屏幕坐标X点 - 水平位移）/ 水平缩放

cirY = （屏幕坐标Y点 - 垂直位移）/ 垂直缩放

源码如下：

;
 
import * as Two from "JS/two";
import * as $ from "JS/jquery";
 
let two;
let mouse;
let isPressed = false;
let originalPositionX = 0;
let originalPositionY = 0;
let map = new Map();
let rect;
 
export function drawGraphic(){
 
  let elem = document.getElementById("draw-shapes");
  let params = {
 
    type: Two.Types['webgl'],
    fullscreen: true,
    autostart: true
  };
 
  two = new Two(params).appendTo(elem);
  mouse = new Two.ZUI(two.scene);
  mouse.addLimits(0.1, 10);
 
  let $stage = $(two.renderer.domElement);
  $stage.bind('mousewheel wheel', function(event){
 
    let e = event.originalEvent;
    e.stopPropagation();
    e.preventDefault();
 
    let dy = (e.wheelDeltaY || -e.deltaY) / 1000;
    mouse.zoomBy(dy, e.clientX, e.clientY);
  });
 
  $stage.bind('mouseup', function(event){
 
    isPressed = false;
  });
  $stage.bind('mouseout', function(event){
 
    isPressed = false;
  });
 
  $stage.bind('mousedown', function(event){
 
    isPressed = true;
    originalPositionX = event.clientX;
    originalPositionY = event.clientY;
 
    let x = event.clientX;
    let y = event.clientY;
 
    for(let value of map){
 
      let xOffset = value[0]._width / 2;
      let yOffset = value[0]._height / 2;
 
      let letX = ((value[0]._translation._x - xOffset) * (two.scene._matrix.elements[0]) + two.scene._matrix.elements[2]);
      let letY = ((value[0]._translation._y - yOffset) * (two.scene._matrix.elements[4]) + two.scene._matrix.elements[5]);
      let letWidth = value[0]._width * two.scene._matrix.elements[0];
      let letHeight = value[0]._height * two.scene._matrix.elements[4];
 
      if(x > letX &&
        y > letY &&
        x < letX + letWidth &&
        y < letY + letHeight
      ){
 
        let r = Math.round(Math.random() * 255);
        let g = Math.round(Math.random() * 255);
        let b = Math.round(Math.random() * 255);
 
        let rgbStr = "rgb(" + r + "," + g + "," + b + ")";
        value[0].fill = rgbStr;
        break;
      }
    }
 
  });
 
  $stage.bind('mousemove', function(event){
 
    if(isPressed){
 
      let boolX = event.clientX - originalPositionX;
      let boolY = event.clientY - originalPositionY;
      mouse.graphicMove(boolX, boolY);
      originalPositionX = event.clientX;
      originalPositionY = event.clientY;
    }
  });
 
  createBtn(1001, 200, 200, 500, "red");
  createBtn(1002, 400, 400, 500, "green");
  createBtn(1003, 600, 600, 500, "blue");
  createBtn(1004, 800, 800, 500, "black");
  createBtn(1005, 1000, 1000, 500, "yellow");
  createBtn(1006, 400, 800, 500, "purple");
}
 
function createBtn(id, x, y, weight, color) {
 
  rect = two.makeRectangle(x, y, 200, 200);
  rect.noStroke();
  rect.fill = color;
  rect.myId = id;
 
  map.set(rect, weight);
}
 
//计算当前屏幕圆心 对应的 图形坐标
function getScreenOriginal(){
 
  let original = {
    x: 0,
    y: 0
  };
 
  original.x = two.width / 2;
  original.y = two.height / 2;
 
  console.log(two.scene._matrix.elements)
 
  //获取水平位移及垂直位移
  //将浏览器上界面坐标转换为two.js的场景坐标,也就是 cirX和cirY为当前界面中点的场景坐标
  let cirX = (original.x - two.scene._matrix.elements[2]) / two.scene._matrix.elements[0];
  let cirY = (original.y - two.scene._matrix.elements[5]) / two.scene._matrix.elements[4];
 
  console.log("cirX:" + cirX + "  cirY:" + cirY);
 
  original.x = cirX;
  original.y = cirY;
 
  return original;
}
 
export function flyToPosition(x, y){
 
  let dot = getScreenOriginal();
  let circle = two.makeCircle(dot.x, dot.y, 10);
  circle.fill = "red";
}