title: How to add ripple effect to PhysicalModel in flutter
body: <p>I was trying to create a login button, which will be animated on pressing on it. But while clicking on the button( on the PhysicalModel), a ripple effect is shown only on the Login text, not entirely on the physical model. How to add ripples to PhysicalModel or remove the ripple effect from MaterialButton ?</p>
  
  <pre><code>PhysicalModel(
              color: Colors.teal,
              borderRadius: BorderRadius.circular(50.0),
              child: MaterialButton(
                     key: _globalKey,
                     child: Text("Login"),
                     onPressed: () {
                          setState(() {
                               if (_state == 0) {
                                      animateButton();
                               }
                          });
                     },
                     elevation: 4.0,
                     minWidth: _width,
                     height: 20.0,
              ),
  )
  </code></pre>