避免对空BufferGeometry更新点时出现错误.

src/Geometry/BufferGeometryUtils.ts

@@ -6,8 +6,7 @@ export namespace BufferGeometryUtils
     export function CreateFromPts(pts: Vector3[]): BufferGeometry
     {
         let geo = new BufferGeometry();
-        let positions = new Float32Array(pts.length * 3);
-        geo.addAttribute('position', new BufferAttribute(positions, 3).copyVector3sArray(pts));
+        UpdatePts(geo, pts);
         return geo;
     }
 
@@ -20,6 +19,12 @@ export namespace BufferGeometryUtils
     export function UpdatePts(geo: BufferGeometry, pts: Vector3[]): boolean
     {
         let bf = geo.getAttribute("position") as BufferAttribute;
+        if (bf === undefined)
+        {
+            let bf = new BufferAttribute(new Float32Array(pts.length * 3), 3).copyVector3sArray(pts);
+            geo.addAttribute('position', bf);
+            return true;
+        }
         if (bf.count >= pts.length)
         {
             bf.copyVector3sArray(pts);