更新一阶导数的实现

src/DatabaseServices/Curve.ts

@@ -35,7 +35,15 @@ export abstract class Curve extends Entity
     GetDistAtPoint(pt: Vector3): number { return; }
     GetParamAtPoint(pt: Vector3): number { return; }
     GetParamAtDist(d: number): number { return; }
-    GetFistDeriv(param: number | Vector3): number { return; }
+
+    /**
+     * 返回曲线在指定位置的一阶导数(在wcs内)
+     * 
+     * @param {(number | Vector3)} param 
+     * @returns {Vector3} 
+     * @memberof Curve
+     */
+    GetFistDeriv(param: number | Vector3): Vector3 { return; }
 
     GetSplitCurves(param: number[] | number): Array<Curve> { return; }
     Extend(newParam: number) { }

src/DatabaseServices/Line.ts

@@ -72,6 +72,11 @@ export class Line extends Curve
         }
     }
 
+    GetFistDeriv(param: number | Vector3): Vector3
+    {
+        return this.EndPoint.sub(this.StartPoint);
+    }
+
     ApplyMatrix(m: Matrix4)
     {
         this.startPoint.applyMatrix4(m);