diff --git a/ArchitectureColoredPainting/src/Renderer/Painting/BvhTree.cpp b/ArchitectureColoredPainting/src/Renderer/Painting/BvhTree.cpp
index 3de220a..82edf94 100644
--- a/ArchitectureColoredPainting/src/Renderer/Painting/BvhTree.cpp
+++ b/ArchitectureColoredPainting/src/Renderer/Painting/BvhTree.cpp
@@ -6,9 +6,6 @@ GLuint BvhTree::getBvhNodeNum() {
 
 void BvhTree::buildBvhTree(BvhTreeData initBound[], int len, GLuint transformParam) {
 	tot = 0; transform = transformParam;
-	for (int i = 0; i < len; i++) {
-		initBound->bound = initBound->boundWithRotation();
-	}
 	root = subBvhTree(initBound, 0, len-1);
 }
 
@@ -21,6 +18,17 @@ QVector4D BvhTree::Union(QVector4D a, QVector4D b) {
 	);
 }
 
+QVector4D BvhTree::merge(BvhPtr lp, BvhPtr rp) {
+	QVector4D a = lp->bound, b = rp->bound;
+	if (lp->isLeaf) {
+		a = BvhTreeData::boundWithRotation(a, lp->getRightSon());
+	}
+	if (rp->isLeaf) {
+		b = BvhTreeData::boundWithRotation(b, rp->getRightSon());
+	}
+	return Union(a, b);
+}
+
 QVector4D BvhTree::calcBound(BvhTreeData initBound[], int l, int r) {
 	QVector4D res = initBound[l].bound;
 	for (int i = l + 1; i <= r; i++) {
@@ -54,13 +62,13 @@ BvhPtr BvhTree::subBvhTree(BvhTreeData initBound[], int l, int r) {
 	int mid = (l + r) >> 1;
 	p->child[0] = subBvhTree(initBound, l, mid);
 	p->child[1] = subBvhTree(initBound, mid+1, r);
-	p->bound = Union(p->child[0]->bound, p->child[1]->bound);
+	p->bound = merge(p->child[0], p->child[1]);
 	return p;
 }
 
 void BvhTree::traverseBvhTree(BvhPtr now, std::vector<GLuint>& children, std::vector<QVector4D>& bounds) {
-	children.push_back(now->getLeftSon(0));
-	children.push_back(now->getRightSon(1));
+	children.push_back(now->getLeftSon());
+	children.push_back(now->getRightSon());
 	bounds.push_back(now->bound);
 	if (now->isLeaf) return;
 	traverseBvhTree(now->child[0], children, bounds);
diff --git a/ArchitectureColoredPainting/src/Renderer/Painting/BvhTree.h b/ArchitectureColoredPainting/src/Renderer/Painting/BvhTree.h
index 4abc27f..de37d18 100644
--- a/ArchitectureColoredPainting/src/Renderer/Painting/BvhTree.h
+++ b/ArchitectureColoredPainting/src/Renderer/Painting/BvhTree.h
@@ -20,15 +20,22 @@ namespace Renderer
 				bound.x(), bound.y(), bound.z(), bound.w(),
 				leftSon, rightSon);
 		}
-		QVector4D boundWithRotation() {
-			double angle = (rightSon & ((1 << 16) - 1)) / static_cast<double>((1 << 16)) * acos(-1);
-			double px = bound.x() * cos(angle) + bound.y() * sin(angle), py = bound.y() * cos(angle) - bound.x() * sin(angle);
-			double qx = bound.z() * cos(angle) + bound.w() * sin(angle), qy = bound.w() * cos(angle) - bound.z() * sin(angle);
+		static QVector4D boundWithRotation(QVector4D bound, GLuint rightSon) {																																											
+			double angle = (rightSon & ((1 << 16) - 1)) / static_cast<double>((1 << 16)) * 2 * acos(-1);
+			double centerX = (bound.x() + bound.z()) / 2, centerY = (bound.y() + bound.w()) / 2;
+			double xCosMin = std::min((bound.x() - centerX) * cos(angle), (bound.z() - centerX) * cos(angle)), 
+				xCosMax = std::max((bound.x() - centerX) * cos(angle), (bound.z() - centerX) * cos(angle));
+			double xSinMin = std::min((bound.x() - centerX) * sin(angle), (bound.z() - centerX) * sin(angle)),
+				xSinMax = std::max((bound.x() - centerX) * sin(angle), (bound.z() - centerX) * sin(angle));
+			double yCosMin = std::min((bound.y() - centerY) * cos(angle), (bound.w() - centerY) * cos(angle)),
+				yCosMax = std::max((bound.y() - centerY) * cos(angle), (bound.w() - centerY) * cos(angle));
+			double ySinMin = std::min((bound.y() - centerY) * sin(angle), (bound.w() - centerY) * sin(angle)),
+				ySinMax = std::max((bound.y() - centerY) * sin(angle), (bound.w() - centerY) * sin(angle));
 			return QVector4D(
-				std::min(px, qx),
-				std::min(py, qy),
-				std::max(px, qx),
-				std::max(py, qy)
+				xCosMin - ySinMax + centerX,
+				yCosMin + xSinMin + centerY,
+				xCosMax - ySinMin + centerX,
+				yCosMax + xSinMax + centerY
 			);
 		}
 		BvhTreeData(QVector4D bound, GLuint leftSon, GLuint rightSon)
@@ -49,13 +56,13 @@ namespace Renderer
 		static bool y_compare(BvhTreeData a, BvhTreeData b) {
 			return a.bound.y() < b.bound.y();
 		}
-		GLuint getLeftSon(int k) {
+		GLuint getLeftSon() {
 			if (isLeaf) {
 				return 0x80000000 + child[0]->lab;
 			}
 			return child[0]->lab;
 		}
-		GLuint getRightSon(int k) {
+		GLuint getRightSon() {
 			if (isLeaf) {
 				return child[1]->lab;
 			}
@@ -84,6 +91,7 @@ namespace Renderer
 		static QVector4D Union(QVector4D a, QVector4D b);
 		BvhPtr subBvhTree(BvhTreeData initBound[], int l, int r);
 		void traverseBvhTree(BvhPtr now, std::vector<GLuint>& children, std::vector<QVector4D>& bounds);
+		QVector4D merge(BvhPtr lp, BvhPtr rp);
 	public:
 		BvhTree() {
 			tot = 0;