diff --git a/src/main/kotlin/org/mechdancer/geometry/rotation3d/Angle3D.kt b/src/main/kotlin/org/mechdancer/geometry/rotation3d/Angle3D.kt
index 5925ec2..054912f 100644
--- a/src/main/kotlin/org/mechdancer/geometry/rotation3d/Angle3D.kt
+++ b/src/main/kotlin/org/mechdancer/geometry/rotation3d/Angle3D.kt
@@ -36,13 +36,6 @@ data class Angle3D(val first: Angle, val second: Angle, val third: Angle, val ax
         }
     }
 
-    /**
-     * 转为内旋
-     *
-     * Intrinsic
-     */
-    fun toEuler() = copy(axesOrder = axesOrder.reverse())
-
     companion object {
         /**
          * 绕 X 轴逆时针旋转 [angle]
diff --git a/src/main/kotlin/org/mechdancer/geometry/rotation3d/Builder.kt b/src/main/kotlin/org/mechdancer/geometry/rotation3d/Builder.kt
new file mode 100644
index 0000000..7df71c8
--- /dev/null
+++ b/src/main/kotlin/org/mechdancer/geometry/rotation3d/Builder.kt
@@ -0,0 +1,33 @@
+package org.mechdancer.geometry.rotation3d
+
+import org.mechdancer.algebra.core.Matrix
+import org.mechdancer.geometry.angle.Angle
+
+/**
+ * 构造内旋 [Angle3D]
+ */
+fun euler(first: Angle, second: Angle, third: Angle, axesOrder: AxesOrder = AxesOrder.ZYZ) =
+    Angle3D(first, second, third, axesOrder.reverse())
+
+/**
+ * 构造外旋 [Angle3D]
+ */
+fun rollPitchYaw(first: Angle, second: Angle, third: Angle, axesOrder: AxesOrder = AxesOrder.XYZ) =
+    Angle3D(first, second, third, axesOrder)
+
+/**
+ * 从矩阵反解旋转角度
+ *
+ * 请见 [Angle3D.fromMatrix]
+ */
+fun Matrix.toRollPitchYaw(axesOrder: AxesOrder) =
+    Angle3D.fromMatrix(this, axesOrder)
+
+/**
+ * 从矩阵反解旋转角度
+ *
+ * 请见 [Angle3D.fromMatrix]
+ */
+fun Matrix.toEuler(axesOrder: AxesOrder) =
+    Angle3D.fromMatrix(this, axesOrder.reverse())
+