Graphics Reference
In-Depth Information
our discussion of WPF 3D in Chapter 6. We have made use of transforms, both
for modeling and for mapping from abstract application coordinates to WPF can-
vas coordinates and then on to physical device coordinates; we will discuss the
underlying mathematics of transformations in subsequent chapters. Finally, we
have seen the advantages of a retained-mode graphics platform for factoring out
a number of tasks that are common to many applications, including simple ani-
mations. Most importantly, we've introduced the basic features of declarative pro-
gramming useful for rapid prototyping that can be conveniently extended to do
geometric modeling and rendering in WPF 3D.
We have not discussed UI callbacks in response to user interactions like button
presses. If such interactions change the thing to be drawn, we must redraw it,
just as we must change the application model's state if they change that. Such
a callback response is now fairly standard for any program that has a UI, which
means most modern programs, and we do not discuss it further.
There's also a second kind of interaction to consider: interaction
within the
viewport,
that is, the clicks and drags that the user may perform on the displayed
scene. To respond appropriately to these, we often need to know things like which
object in the scene the user clicked on, and where the drag started and ended.
Determining which object was clicked is known as
pick correlation,
and we dis-
cuss this in the context of 3D in Chapter 6. Responding to click-and-drag oper-
ations in a 3D scene often requires careful work with the modeling transform
hierarchy; we discuss some examples in Chapter 21.
There are a great many other graphics packages in the world, and you're likely
to encounter at least a few as you work with computer graphics. We encourage
you to browse the Web and read about OpenGL, for instance, and Swing, to get
a sense of the variety of features provided by various packages and some of the
commonality and differences among them.
