Update README.md

Author: Rohit Malhotra

README.md

@@ -445,6 +445,45 @@ CONFIG = {
 
 ### 3D Graphing
 
+```python
+from big_ol_pile_of_manim_imports import *
+
+class ThreedSurface(ParametricSurface):
+
+    def __init__(self, **kwargs):
+        kwargs = {
+        "u_min": -2,
+        "u_max": 2,
+        "v_min": -2,
+        "v_max": 2,
+        "checkerboard_colors": [BLUE_D]
+        }
+        ParametricSurface.__init__(self, self.func, **kwargs)
+
+    def func(self, x, y):
+        return np.array([x,y,x**2 - y**2])
+
+    def tangentX(self, x, y):
+        return 2*x
+        
+class Test(ThreeDScene):
+
+    def construct(self):
+        self.set_camera_orientation(0.6, -0.7853981, 86.6)
+
+        surface = ThreeDSurface()
+        self.play(ShowCreation(surface))
+
+        d = Dot(np.array([0,0,0]), color = YELLOW)
+        self.play(ShowCreation(d))
+
+
+        self.wait()
+        self.move_camera(0.8*np.pi/2, -0.45*np.pi)
+        self.begin_ambient_camera_rotation()
+        self.wait(9)
+```
+
 **Click for results on YouTube:**
 
 [![Youtube video link](https://img.youtube.com/vi/_XMEQRshlp4/0.jpg)](https://www.youtube.com/watch?v=_XMEQRshlp4)