diff --git a/README.md b/README.md
index d11951b..4fc8dc8 100644
--- a/README.md
+++ b/README.md
@@ -29,8 +29,8 @@ find_package(Qt${QT_VERSION_MAJOR} REQUIRED COMPONENTS Widgets)
 #include "bvh.h"
 #include "singularityJudger.h"
 // 创建两个曲面
-tinynursb::RationalSurface<float> s;
-tinynursb::RationalSurface<float> f;
+tinynurbs::RationalSurface<float> s;
+tinynurbs::RationalSurface<float> f;
 // 曲面初始化
 ...
 
diff --git a/main.cpp b/main.cpp
index 2fc0c0d..b97b449 100644
--- a/main.cpp
+++ b/main.cpp
@@ -188,11 +188,11 @@ int main() {
     RationalSurface<float> s;
     RationalSurface<float> f;
 
-    int level = 6;
+    int level = 9;
     printf("level: %d, sample cnt: %d * %d\n", level, int(pow(2, level - 1)), int(pow(2, level - 1)));
 
     ifstream fin;
-    fin.open(R"(intersectTest\case2\surfaces.txt)");
+    fin.open(R"(intersectTest\casea1\surfaces.txt)");
 
     string str;
     string tmp;
diff --git a/src/bvh.cpp b/src/bvh.cpp
index 6471e54..e07f61e 100644
--- a/src/bvh.cpp
+++ b/src/bvh.cpp
@@ -23,8 +23,8 @@ void BVH::recursiveBuild(int level, int idx, int idx_u, int idx_v) {
         int firstChild = 4 * idx + 1;
         int halfRange = int(std::pow(2, maxLevel - level - 1)); // 当前层的曲面片的边长采样宽度的一半
         recursiveBuild(level + 1, firstChild, idx_u, idx_v);
-        recursiveBuild(level + 1, firstChild + 1, idx_u, idx_v + halfRange);
-        recursiveBuild(level + 1, firstChild + 2, idx_u + halfRange, idx_v);
+        recursiveBuild(level + 1, firstChild + 1, idx_u + halfRange, idx_v);
+        recursiveBuild(level + 1, firstChild + 2, idx_u, idx_v + halfRange);
         recursiveBuild(level + 1, firstChild + 3, idx_u + halfRange, idx_v + halfRange);
         for (int i = 0; i < 4; i++)
             bound = Union(bound, tree[firstChild + i].bound);