MCS-170 The Nature of Computer Science
Alice Lecture 5
1. Object Posing,
Camera and Animation Control
- Event Handling (conclude discussion)
- Object Creation, Manipulation, and Posing
- Camera Control
- Object Creation, Manipulation,
Creation: So far, we have used the Classes of Objects that we
find in the Local Gallery.
There is an extensive collection of Classes available online. These can
be accessed from within the Gallery directory. Within the Alice
program, click on Home when
adding an Object. There will be two (or more) directory icons - one of
these is the Local Gallery,
which resides on the computer on which Alice is running. Another
will be called Web Gallery.
This directory contains Classes that you can access at the central
Use the Web Gallery to create
a water world with a shark, manta ray, coral, and fish, along with an
ocean floor object.
- Object and
Scene Manipulation: Often, it is hard to see how to
position objects in our scene. We can create multiple "views" of
the scene by using the Quad View
feature of Alice. In the upper right corner of the Alice window
we select "quad view" to change the viewing window into a four-pane
viewing window. The viewpoints show the scene from (in
counter-clockwise order from the upper-left window) The Camera's view,
The Top of the scene, The Front of the scene, and The Right of the
- Note that the toolbox of mouse controls now has a second row
with two new buttons -- a scroll button and a zoom button. These
two buttons can be used to adjust the three non-camera viewpoints.
In our fishy example, go to Quad view and use the controls to position
the shark above the coral and then position the manta ray and fish to
the right of the shark, about five meters away. Have the shark
face in the direction of the other creatures.
Posing -- It is often tedious to use move, turn, roll commands
to make an object transform in some way, for example to have a person
raise their arm. For this reason, Alice allows one to pose objects and then recall the
poses at later points in the animation. To pose an object, we click on
the capture pose button in the
Details panel of the object. Then, we can drag the new pose
tile that gets created into an animation.
In our fishy example, suppose we want the shark to swim toward the
fish, open its mouth and the fish to raise its flippers in alarm.
Here (sharkPose.a2w) is a world where we
create two poses for this behavior.
- Note: It is often
difficult to click precisely on an object to pose its parts. There is
another way to manipulate an object -- using popup menus.
Suppose we want to make the dorsal fin of our fish twice as big. It is
difficult to get the mouse to click on the dorsal (as it is tiny) to
select it. Another way to select it is to select it from the Class tree
list in the upper left corner of the Alice window. Then, if we
right-click on the dorsal fin tab, a menu will popup, allowing us to do
a wide variety of actions on the dorsal fin.
- Camera Control
- Controlling the camera can be one of the more difficult parts
of using Alice. Here are a few pointers:
the point of view: Every good director knows that a
dynamic film needs to have the camera move within the scene, from one
point of view to another. This can be accomplished by dropping dummy objects at positions where
you want the camera.
A scene with a three bunnies, where we want to move the point of view
from one to another. Drop 4 dummy objects for camera - 1 at
initial position, and three at each bunny. (Demonstrate) Here is an
example world (bunnyCamera.a2w)
an object: We can have the camera track an object in the
scence by telling the camera to constrain
to point at the object.
In our biplane example (biplane.a2w)from the
Event Handling lecture, we use this camera method to have the camera
track the plane, making sure the duration of the method is long enough
to last out the scene.