// Import some data
electrondensity = Import("watermolecule");

// Partition the data
electrondensity = Partition(electrondensity);

// Create a camera
camera = AutoCamera(electrondensity,width=4);

// Take a slab of thickness 0 from position 9 in the z dimension
slab = Slab(electrondensity, "z", 9, 0);

// Color the slab
slab = AutoColor(slab);

//create an image of the colored slab
image = Render(slab,camera);




//Create a set of contours on the slab at values of 0.2, 0.3,....
contours = Isosurface(slab,{0.2, 0.3, 0.4, 0.7, 1.0});

// Create an image of the contours
contours = Render(contours,camera);

// Overlay the two images and display
together = Overlay(image,contours);
Display(together);




// Now create two new images to do chroma-keying
camera1 = Camera([1, 0, -1], [1, 0, 10], width = 8, 
                 resolution = 400, aspect = 1);
image1 = Render(slab, camera1);
Display(image1);
// the second image has the slab much smaller, near the upper right of 
// the image
camera2 = Camera([-4, 0, -1], [1, 0, 10], width = 20,
                 resolution = 400, aspect = 1);
image2 = Render(slab, camera2);
Display(image2);

// we overlay the two images, and see image2 only where image1 is black
together = Overlay(image2, image1, blend = [0 0 0]);
Display(together);



// Another example of the functionality of Overlay
 
// Create a grid
grid = Construct([0 0],[1 1],[240 320],[0 0 0]);

// Create a black image field
black = Color(grid,"black"); 

// Create a white image field
white = Color(grid,"white"); 

// Create a red image field
red = Color(grid,"red"); 

// Create a grid with data values that vary with the sine in the horizontal 
// direction
grid = Mark(grid,"positions");
sine = Compute("0.5+0.5*sin(3.14/120*$0.x)", grid);

// Blend black into white using the sinusoidal blend field
d = Overlay (black,white,sine);
Display(d);
sineblend = d;

// Overlay red into sineblend everywhere white is found in sineblend.
d = Overlay(red,sineblend,"white");
Display(d);