使用three.js 绘制三维带箭头线的详细过程

需求：这个需求是个刚需啊！在一个地铁场景里展示逃生路线，这个路线肯定是要有指示箭头的，为了画这个箭头，我花了不少于十几个小时，总算做出来了，但始终有点问题。我对这个箭头的要求是，无论场景拉近还是拉远，这个箭头不能太大，也不能太小看不清，形状不能变化，否则就不像箭头了。

使用到了 three.js 的 Line2.js 和一个开源库MeshLine.js

部分代码：

DrawPath.js：

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283

/**  * 绘制路线  */ import * as THREE from '../build/three.module.js'; import { MeshLine, MeshLineMaterial, MeshLineRaycast } from '../js.my/MeshLine.js'; import { Line2 } from '../js/lines/Line2.js'; import { LineMaterial } from '../js/lines/LineMaterial.js'; import { LineGeometry } from '../js/lines/LineGeometry.js'; import { GeometryUtils } from '../js/utils/GeometryUtils.js'; import { CanvasDraw } from '../js.my/CanvasDraw.js'; import { Utils } from '../js.my/Utils.js'; import { Msg } from '../js.my/Msg.js'; let DrawPath = function () {     let _self = this;     let _canvasDraw = new CanvasDraw();     let utils = new Utils();     let msg = new Msg();     this._isDrawing = false;     this._path = [];     this._lines = [];     this._arrows = [];     let _depthTest = true;     let _side = 0;     let viewerContainerId = '#cc';     let viewerContainer = $(viewerContainerId)[0];     let objects;     let camera;     let turn;     let scene;     this.config = function (objects_, camera_, scene_, turn_) {         objects = objects_;         camera = camera_;         turn = turn_;         scene = scene_;         this._oldDistance = 1;         this._oldCameraPos = { x: camera.position.x, y: camera.position.y, z: camera.position.z }     }     this.start = function () {         if (!this._isDrawing) {             this._isDrawing = true;             viewerContainer.addEventListener('click', ray);             viewerContainer.addEventListener('mousedown', mousedown);             viewerContainer.addEventListener('mouseup', mouseup);         }         msg.show("请点击地面画线");     }     this.stop = function () {         if (this._isDrawing) {             this._isDrawing = false;             viewerContainer.removeEventListener('click', ray);             viewerContainer.addEventListener('mousedown', mousedown);             viewerContainer.addEventListener('mouseup', mouseup);         }         msg.show("停止画线");     }     function mousedown(params) {         this._mousedownPosition = { x: camera.position.x, y: camera.position.y, z: camera.position.z }     }     function mouseup(params) {         this._mouseupPosition = { x: camera.position.x, y: camera.position.y, z: camera.position.z }     }     function ray(e) {         turn.unFocusButton();         let raycaster = createRaycaster(e.clientX, e.clientY);         let intersects = raycaster.intersectObjects(objects.all);         if (intersects.length > 0) {             let point = intersects[0].point;             let distance = utils.distance(this._mousedownPosition.x, this._mousedownPosition.y, this._mousedownPosition.z, this._mouseupPosition.x, this._mouseupPosition.y, this._mouseupPosition.z);             if (distance < 5) {                 _self._path.push({ x: point.x, y: point.y + 50, z: point.z });                 if (_self._path.length > 1) {                     let point1 = _self._path[_self._path.length - 2];                     let point2 = _self._path[_self._path.length - 1];                     drawLine(point1, point2);                     drawArrow(point1, point2);                 }             }         }     }     function createRaycaster(clientX, clientY) {         let x = (clientX / $(viewerContainerId).width()) * 2 - 1;         let y = -(clientY / $(viewerContainerId).height()) * 2 + 1;         let standardVector = new THREE.Vector3(x, y, 0.5);         let worldVector = standardVector.unproject(camera);         let ray = worldVector.sub(camera.position).normalize();         let raycaster = new THREE.Raycaster(camera.position, ray);         return raycaster;     }     this.refresh = function () {         if (_self._path.length > 1) {             let distance = utils.distance(this._oldCameraPos.x, this._oldCameraPos.y, this._oldCameraPos.z, camera.position.x, camera.position.y, camera.position.z);             let ratio = 1;             if (this._oldDistance != 0) {                 ratio = Math.abs((this._oldDistance - distance) / this._oldDistance)             }             if (distance > 5 && ratio > 0.1) {                 console.log("======== DrawPath 刷新 ====================================================")                 for (let i = 0; i < _self._path.length - 1; i++) {                     let arrow = _self._arrows[i];                     let point1 = _self._path[i];                     let point2 = _self._path[i + 1];                     refreshArrow(point1, point2, arrow);                 }                 this._oldDistance = distance;                 this._oldCameraPos = { x: camera.position.x, y: camera.position.y, z: camera.position.z }             }         }     }     function drawLine(point1, point2) {         const positions = [];         positions.push(point1.x / 50, point1.y / 50, point1.z / 50);         positions.push(point2.x / 50, point2.y / 50, point2.z / 50);         let geometry = new LineGeometry();         geometry.setPositions(positions);         let matLine = new LineMaterial({             color: 0x009900,             linewidth: 0.003, // in world units with size attenuation, pixels otherwise             dashed: true,             depthTest: _depthTest,             side: _side         });         let line = new Line2(geometry, matLine);         line.computeLineDistances();         line.scale.set(50, 50, 50);         scene.add(line);         _self._lines.push(line);     }     function drawArrow(point1, point2) {         let arrowLine = _self.createArrowLine(point1, point2);         var meshLine = arrowLine.meshLine;         let canvasTexture = _canvasDraw.drawArrow(THREE, renderer, 300, 100); //箭头         var material = new MeshLineMaterial({             useMap: true,             map: canvasTexture,             color: new THREE.Color(0x00f300),             opacity: 1,             resolution: new THREE.Vector2($(viewerContainerId).width(), $(viewerContainerId).height()),             lineWidth: arrowLine.lineWidth,             depthTest: _depthTest,             side: _side,             repeat: new THREE.Vector2(1, 1),             transparent: true,             sizeAttenuation: 1         });         var mesh = new THREE.Mesh(meshLine.geometry, material);         mesh.scale.set(50, 50, 50);         scene.add(mesh);         _self._arrows.push(mesh);     }     function refreshArrow(point1, point2, arrow) {         let arrowLine = _self.createArrowLine(point1, point2);         var meshLine = arrowLine.meshLine;         let canvasTexture = _canvasDraw.drawArrow(THREE, renderer, 300, 100); //箭头         var material = new MeshLineMaterial({             useMap: true,             map: canvasTexture,             color: new THREE.Color(0x00f300),             opacity: 1,             resolution: new THREE.Vector2($(viewerContainerId).width(), $(viewerContainerId).height()),             lineWidth: arrowLine.lineWidth,             depthTest: _depthTest,             side: _side,             repeat: new THREE.Vector2(1, 1),             transparent: true,             sizeAttenuation: 1         });         arrow.geometry = meshLine.geometry;         arrow.material = material;     }     this.createArrowLine = function (point1, point2) {         let centerPoint = { x: (point1.x + point2.x) / 2, y: (point1.y + point2.y) / 2, z: (point1.z + point2.z) / 2 };         let distance = utils.distance(point1.x, point1.y, point1.z, point2.x, point2.y, point2.z);         var startPos = { x: (point1.x + point2.x) / 2 / 50, y: (point1.y + point2.y) / 2 / 50, z: (point1.z + point2.z) / 2 / 50 }         let d = utils.distance(centerPoint.x, centerPoint.y, centerPoint.z, camera.position.x, camera.position.y, camera.position.z);         if (d < 2000) d = 2000;         if (d > 10000) d = 10000;         let lineWidth = 100 * d / 4000;         //console.log("d=", d);         let sc = 0.035;         var endPos = { x: startPos.x + (point2.x - point1.x) * sc * d / distance / 50, y: startPos.y + (point2.y - point1.y) * sc * d / distance / 50, z: startPos.z + (point2.z - point1.z) * sc * d / distance / 50 }         var arrowLinePoints = [];         arrowLinePoints.push(startPos.x, startPos.y, startPos.z);         arrowLinePoints.push(endPos.x, endPos.y, endPos.z);         var meshLine = new MeshLine();         meshLine.setGeometry(arrowLinePoints);         return { meshLine: meshLine, lineWidth: lineWidth };     }     this.setDepthTest = function (bl) {         if (bl) {             _depthTest = true;             this._lines.map(line => {                 line.material.depthTest = true;                 line.material.side = 0;             });             this._arrows.map(arrow => {                 arrow.material.depthTest = true;                 arrow.material.side = 0;             });         } else {             _depthTest = false;             this._lines.map(line => {                 line.material.depthTest = false;                 line.material.side = THREE.DoubleSide;             });             this._arrows.map(arrow => {                 arrow.material.depthTest = false;                 arrow.material.side = THREE.DoubleSide;             });         }     }     /**      * 撤销      */     this.undo = function () {         scene.remove(this._lines[this._lines.length - 1]);         scene.remove(this._arrows[this._arrows.length - 1]);         _self._path.splice(this._path.length - 1, 1);         _self._lines.splice(this._lines.length - 1, 1);         _self._arrows.splice(this._arrows.length - 1, 1);     } } DrawPath.prototype.constructor = DrawPath; export { DrawPath }

show.js中的部分代码：

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38

let drawPath;     //绘制线路     drawPath = new DrawPath();     drawPath.config(         objects,         camera,         scene,         turn     );     $("#rightContainer").show();     $("#line-start").on("click", function (event) {         drawPath.start();     });     $("#line-stop").on("click", function (event) {         drawPath.stop();     });     $("#line-undo").on("click", function (event) {         drawPath.undo();     });     $("#line-show").on("click", function (event) {         drawPath.refresh();     });     let depthTest = true;     $("#line-depthTest").on("click", function (event) {         if (depthTest) {             drawPath.setDepthTest(false);             depthTest = false;         } else {             drawPath.setDepthTest(true);             depthTest = true;         }     }); setInterval(() => {     drawPath && drawPath.refresh(); }, 100);

效果图：

 

还是有点问题：

 

虽然这个效果图中，场景拉近，箭头有点大，但是最大大小还是做了控制的，就是这个形状有点问题，可能是视角的问题。

我期望的效果应该是这样的，就是无论从什么角度看，箭头不要变形：