Author：赵志乾
Date：2024-06-25
Declaration：All Right Reserved！！！

1. 类图

2. 代码解析

//***********************核心字段************************
// MarkupSegment起点坐标
double startX;
double startY;
double startZ;
double endX;
double endY;
double endZ;

//***********************构造函数**************************
// 指定MarkupSegment的起止点坐标
MarkupSegment(double startX, double startY, double startZ, double endX, double endY, double endZ) {
	this.startX = startX;
	this.startY = startY;
	this.startZ = startZ;
	this.endX = endX;
	this.endY = endY;
	this.endZ = endZ;
}
// 设置MarkupSegment起点坐标
public final void setStart(double x, double y, double z) {
	// MarkupSegment在initialize之后不允许再修改
	this.checkForModify();
	this.startX = x;
	this.startY = y;
	this.startZ = z;
}
// 设置MarupSegment终点坐标
public final void setEnd(double x, double y, double z) {
	// MarkupSegment在initialize之后不允许再修改
	this.checkForModify();
	this.endX = x;
	this.endY = y;
	this.endZ = z;
}

//*******************************MarkupSegment上的点**************************
// 获取MarkupSegment的长度
public final double length() {
	return super.length();
}
// 获取距离起点偏移量为offset的点坐标
public final Position getPositionAtOffset(double offset, Position out) {
	// 校验offset是否合法
	if(offset< -1.0E-4 || offset>this.length()+1.0E-4){
		error("offset is out of range!");
	}
	
	if(out==null){
		out = new Position();
	}
	// 子类决定计算方式
	this.getPositionAtOffsetInternal(offset, out);
	return out;
}