Update Exercise 4 (submission format)

ex4/README.md

@@ -16,7 +16,7 @@ The result should look something like this:
 <img src="img/skull.png" width="300">. 
 
 
-**Summary of your Tasks:** Insert a contour filter into the pipeline. Assign its value based on the dataset.
+**Summary of your Tasks:** Insert a contour filter into the pipeline. Assign its value based on the dataset. Save your submission code as `task1.py`.
 
 ## Task 2: Interactive Contours (2P)
 Frequently, one static contour surface is not sufficient to see all details in the data. Therefore, we would like to change the contour value interactively, with the surface updating accordingly.
@@ -26,11 +26,11 @@ Your widget should also get its minimum and maximum values from the dataset. One
 <img src="img/contourvalue.gif" width="300">. 
 
 
-**Summary of your Tasks:** Add a slider which changes the contour value and the corresponding surface interactively. 
+**Summary of your Tasks:** Add a slider which changes the contour value and the corresponding surface interactively. Save your code as `task2.py`.
 
 
 ## Task 3: Clipping (2P)
-Contour can surfaces overlap each other and detail on the inside is lost. This is called *occlusion*. A simple way to address this is to add a so-called *clipping plane* in Z-direction (up/down), i.e. to remove all graphical output on one side of the plane.
+Contour surfaces can overlap each other such that detail on the inside is lost. This is called *occlusion*. A simple way to address this is to add a so-called *clipping plane* in Z-direction (up/down), i.e. to remove all graphical output on one side of the plane.
 This can be achieved with a ```vtkClipPolyData``` filter. This filter relies on an implicit function called ```vtkPlane```. Therefore, create a plane in Z-direction and use the vtkClipPolyData filter with this plane.
 Add another slider with sensible values to control this clipping. Where can you find these values and what do you have to pay attention to?
 
@@ -39,4 +39,4 @@ The result should look like this:
 <img src="img/zClip.gif" width="300">. 
 
 
-**Summary of Tasks:** Add another slider which controls a ```vtkClipPolyData``` filter in Z-dimension. What is the extent of this dimension and what is the maximum value of the clipping plane?
+**Summary of Tasks:** Add another slider which controls a ```vtkClipPolyData``` filter in Z-dimension. What is the extent of this dimension and what is the maximum value of the clipping plane? Save your submission code as `task3.py`.