Use the Combine Command in the Object menu of Microsoft Expression Blend to create interesting effects - Combine command can be used with shapes or paths to make your drawing or artwork more powerful.
Combine shapes with other shapes or paths
Expression Blend has five ways to combine shapes or paths. You can use Unite, Divide, Intersect, Subtract or Exclude Overlap command to produce stunning effect.
To combine them, choose the Selection tool, select all the shapes and paths that you want, and then choose Objects -> Combine.
I will demonstrate each command with help of a diagram to make you understand in an easy and interesting way.
Unite: It maintains the outer stroke of all the selected objects while eliminating the interior strokes and uses the fill of the topmost shape or path as the fill for the entire new object, as shown in figure.
Draw a rectangle on the artboard. After drawing the rectangle draw a circle with the help of ellipse tool on Toolbox. You can hold the Shift key to have perfect circle drawing ellipse.
Place the circle on top of the rectangle. Select both the objects. After that choose Objects -> Combine -> Unite command to get the desired effect. Figure 1.1 shows a picture of a door has round shaped on the top with the help of combining rectangle and circle with help of Unite command.
I will show one more interesting example of Unite command. Lets make a engine with the help of Unite Command.
Draw a rectangle on the artboard. Place a small rectangle on top of the rectangle as shown in the pictures. Make two circles and place on the drawing to show the picture of a train engine Figure 1.2.
Select all the objects and choose Objects -> Combine -> Unite. See the interesting result in Figure 1.3.
Divide: It maintains all strokes, and uses the fill of the topmost shape or path as the fill of all selected shapes and paths.
Make three circles and select them as shown in Figure 2.1.
Now choose Objects -> Combine -> Divide. See the interesting result in Figure 2.1.
Intersect: Keeps only the segment of the shapes or paths that overlap all the selected shapes or paths. If no such segment exists, then the intersect pertain to the segment of shapes or paths which overlap and contain the topmost shape or path.
Draw a rectangle giving a gray effect as if it is a candle. Than draw two rectangles with gradient effect of a flame as shown in figure 3.1. Place both circle near as they are intersecting each other.
Select both circles and choose Objects -> Combine -> Intersect. Place the flame shape on top of the rectangle, which we made as candle. See the interesting result in Figure 2.1 a candle with a beautiful flame.
Subtract: Leaves only the segment or segments of the topmost shape or path that are overlapping another shape or path.
I will explain subtract with the help of a good example. A half glowing sun can be made with help of it. Make two circles and place one circle over the other circle as shown in figure 4.1.
Select both the circles and choose Objects -> Combine -> Subtract. See the effect a beautiful half sun with glowing effect.
Exclude Overlap: Excludes areas overlapped by two shapes or paths or both. Areas overlapped by three shapes, paths, or both are not excluded.
To understand Exclude Overlap command draw petal shape with the help of Ellipse. Copy that petal shape ellipse and rotate with the help of Transform Rotate in the Property Panel. Give it some angle say 15 degree for each petal as shown in the Figure 5.1
Now select the entire petal shape ellipse and Objects -> Combine -> Exclude Overlap. See the effect a beautiful design.