Merge pull request #26 from tinkerfuroc/vision_doc

quaternion from vector

docs/Documentation/Vision/cheat_sheet.md

@@ -183,3 +183,40 @@ Get quaternion from euler angles. Copied from ROS2 wiki.
   </TabItem>
 
 </Tabs>
+
+### Quaternion from Vector
+
+Get quaternion from a vector.
+
+<Tabs>
+  <TabItem value="python" label="Python" default>
+
+  ```python
+    import tf_transformations
+
+    rotation = np.eye(4)
+    # (x0, y0, z0) ------> (x1, y1, z1)
+    # x, y, z = x1 - x0, y1 - y0, z1 - z0
+    x, y, z = x0 - x1, y0 - y1, z0 - z1 # I don't know why but this one works
+
+    # x-axis
+    rotation[:3, 0] = np.array([x, y, z])
+    # z-axis, must be (0, 0, 1) when z == 0
+    rotation[:3, 2] = np.array([-x * z, - y * z, x ** 2 + y ** 2])
+    # y-axis, calculated from x and z
+    rotation[:3, 1] = np.array([y, -x, 0])
+    q = tf_transformations.quaternion_from_matrix(rotation)
+  ```
+
+  </TabItem>
+
+  <TabItem value="c++" label="C++">
+
+  ```c++
+  GUGUGU
+  ```
+
+  </TabItem>
+
+</Tabs>
+