Transcript Introduction to Alice

Introduction to CSCI 1
How this class will work
http://users.drew.edu/sbradsha/CSCI1-Spring2007/
Alice
A modern programming tool
3-D graphics
3-D models of objects
Animation
Objects can be made to move around
the virtual world (a video game or
simulation implemented in 3-D)
The basics of programming
A computer program is a set of instructions
that tell the computer what to do
It is important to write your programs in an
“elegant” fashion.
Huh?
Two primary functions:
To tell the computer what to do
To tell other humans what you want the
computer to do
Elegant programs
A program is elegant if other humans can
easily understand and appreciate the
intentions of the original programmer.
Your goal should be to make your program
easy to read, even by someone not a
programmer
Should not require any head scratching
Programs composed from simple ideas
A list of instructions like a recipe
Ifs (e.g., if it is raining, take an umbrella)
Repeating behavior (e.g., while there are
cookies on your plate, keeping eating
cookies) usually called looping or
iteration
Breaking things up into smaller pieces
Compute a result
Simple ideas, cont’d
Programming is just using these ideas in
various combinations
Most computers understand only about
100 distinct instructions
The millions of programs that run on a
computer use these instructions in
different orders and combinations
Like chess in this way
Alice concepts
Concept: Virtual world
Video game or simulation implemented in
3D
2D vs. 3D
Virtual world, cont’d
Virtual worlds provide an environment that
allow us to simulate the type of interactions
with which we are familiar in the real world.
Concept: Object
An "object" is
any thing that can be identified as unique
from other things
How is an object unique?
has a name
has properties:
width, height, color, location
can perform actions (methods):
associated actions it can perform
tasks it can carry out
Object Parts
Objects may be composed of parts
3D models
In Alice, nearly all objects are represented by
3D models
These are the animals, people, cars, anvils,
etc. that you add to a world
3D models are found in the Alice galleries
Alice is not a 3D graphics drawing program
With the exception of he-builder and shebuilder we use pre-defined models
Concept: 3 Dimensions, 6 Directions
A 3D object has
3 dimensions
height, width, depth
6 degrees of freedom (directions of movement)
Concept: Center of an
object
At the center of mass
Where it stands on the ground
Where it is held
Distance between objects is
measured from their centers
An object’s position in the world
is given by its center
Class
Objects are categorized into classes
peter
paul
Person
mary
spike
Each object is
an instance of the class.
scottie
Dogs
fluffy
All objects in a class have similar properties
and generally can perform the same tasks.
Appendix A: Exploring Alice
World 1:Open World…Week1AppendixA_FirstWorld.a2w
Play
Appendix A: exploring Alice
Notice the Object Tree contains all of the objects in the world.
The camera and the
light are in every
Alice word.
Object Parts: A closer look
Introduction to the "code"
Look at Hare in the Object tree
Expand to find the hare's ears
Notice that the hare's left ear moves
forward and back in this animation.
Let's modify this animation
Modifying code
Let's change the movement to go left and
right instead of forward and backward.
PLAY
Modifying code
Let’s make the RIGHT ear move.
Modifying code
Finally
Let's change this one last time so that the
RIGHT ear moves forward and back.
PLAY
Interactive World
Open New World
Open AppendixA_DancingBee.a2w
Play
Press Up-Arrow key
Press space bar
Two types of worlds
Movie World
movie runs from beginning to end
Interactive World
you choose how animation runs (events)
Creating your own world
File menuNew World
grass template
Save World As MyFirstTry
Navigate to the appropriate folder
Creating your own world
Add Objects
Search Gallery allows you to choose
objects
Click
Folder
Objects
An "object" is
any thing that can be identified as unique from
other things
How is an object unique?
has a name
has properties:
width, height, color, location
can perform actions (methods):
associated actions it can perform
tasks it can carry out
Galleries
Classes (3D models) are found in the galleries
Local gallery (installed with the software)
Minimum or complete options
Web gallery
Choose Local Gallery
PeopleAdd
snowMan (2 ways to add to world)
Drag snowman to world
Click and Add Instance to world
snowWoman
Controls
Click on snowman
and experiment with
controls.
Click on snowWoman
and check
"affectparts"
delete her hat.
Controls
Controls
Camera
Top
Side
Front
More controls
Moving the camera
changes the view of
the world
Go slowly.
New worlds
Add all objects when you create the world.
Use mouse and camera controls to
arrange objects at the scene.
Assignment
Read (before the next class session)
Chapter 1
Section 1, Introduction to Alice
Section 2, Alice Concepts
Tips & Techniques 1, Special Effects
Object-oriented programming and Alice
In designing modern software we work
from an algorithm.
An algorithm is a plan for solving a
problem by following a sequence of steps
To help manage the growing complexity
of software, computer scientists
introduced the concept of OOP some time
ago
OOP
An object can be something in the physical world or
just an abstract idea
Airplane (auto-pilot program)
A bank transaction (ATM software)
The code that manipulate the properties of an
object are called the object’s methods
We can think of an object as a collection of its
properties and methods
The values stored in the properties of an object are
called collectively know as the object’s state
OOP algorithms define interactions between objects
An OO program uses objects as tools to do its work
Exploring the Alice Interface
Alice is an example of an Integrated
Development Environment (IDE)
An IDE is a computer program used to
write other computer programs
The Alice IDE is often called the Alice
interface
Welcome to Alice! dialog
Tutorials tab
Recent worlds tab
Examples tab
Open a world tab
Navigation
Folders
Files
Controls
World Window
Events Area
Object Tree
Details Area
Editor Area
Object Tree
Details Area
Editor Area
Events Area
event trigger
event handler
event handler
event handler
World Window
Trashcan and Clipboard
Menus
In-class exercise 1
On the course web site under week 1