<h4> Line3.js中 closestPointToPointParameter() 函数意义 ;返回一个基于点投影到线段上的点的参数(就是参数point投影到线段的位置),
<hr> 如果 clampToLine 为true,那么返回值将是0和1之间</h4>
<script>
/*----------------- 函数简单测试 -----------------*/
function closestPointToPointParameter(point) {
this.start = new Vector3(0,0,0);
this.end = new Vector3(2,0,0);
var startP = new Vector3();
var startEnd = new Vector3();
startP.subVectors(point,this.start);
startEnd.subVectors(this.end,this.start);
/* a,b两向量点积 |a|*|b|*cosθ; 由于它们的角度为0,所以cosθ为1;
* a * b = |a|*|b|;得到的是两个长相乘
* */
var startEnd2 = startEnd.dot(startEnd);
console.log(startEnd2);
/*它两的点积得到的是两个向量所形成的矩形面积
* */
var startEnd_startP = startEnd.dot(startP);
console.log(startEnd_startP);
var t = startEnd_startP / startEnd2;
/* // t大于1返回1,小于0返回0,在0 - 1范围间返回它本身
if ( clampToLine ) {
t = THREE.Math.clamp( t, 0, 1 );
}
* */
console.log(t);
}
var Vector3 = function(x,y,z){
this.x = x;
this.y = y;
this.z = z;
}
Vector3.prototype.subVectors = function(a,b){
this.x = a.x - b.x;
this.y = a.y - b.y;
this.z = a.z - b.z;
return this;
}
Vector3.prototype.dot = function(v){
return this.x * v.x +this.y * v.y + this.z * v.z;
}
var point = new Vector3(1,1,0);
closestPointToPointParameter(point);
</script>
Threejs Line3.js 中 closestPointToPointParameter 函数的意义
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转载自blog.csdn.net/qq_25909453/article/details/82427715
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