Visual programming

CS320n – Elements of Visual
Programming
Introduction to Alice
Mike Scott
(Slides 1-1)

Visual Programming Introduction to Alice 2
What We Will Do Today
• look at the Alice programming
environment
• create some simple programs in Alice

What is Alice?
• Named in honor of Lewis Carroll’s (pen
name) Alice in Wonderland
– Charles Lutwidge Dodgson was also a
mathematician and logician
• A modern programming tool
– purpose of tool, learn how to program, write
algorithms
– 3-D graphics
– 3-D models of objects
• Animation
– Objects can be made to move around virtual
world (a simulation or a video game. Simple
Pixar.)

Computer Programs
• General purpose programming languages
can be used for almost any task
• Alice is not a general purpose
programming language.
– It is an application specific language
– designed for a specific task, creating 3D
animations
– lots of application specific languages.
Example: language for working with DNA data

Fundamental Tools
• All languages contain these elements
1. list of instructions – “Pack lunch, pack snack, put
homework in backpack.”
2. decision making – “If I didn’t shave yesterday,
shave today.”
3. repetition of behavior – “Do a load of laundry until
there is no more dirty laundry.”
4. modularization. Big rocks into little rocks. “To do a
load of laundry: gather clothes, get clothes right-
side out, put clothes of similar color into washing
machine…”
5. Generalization: Solve many different problems with
one set of instructions
6. Compute a result – “How much is it going to cost to
fill up my car with gas?”

What does Alice run on?
• Alice is free.
• Alice is written in Java
– only working versions are for PCs and Macs
with OSX 10.3 or higher (relatively new, may
still have bugs)
– Sorry, no Linux, yet
– the book comes with a copy of Alice for
Windows machines
– www.alice.org
– also on the computers in the CS Elements lab

Fast Start Up
• Can quickly learn to create
– a simple animation in a matter of minutes
– a non-trivial animation in a few class periods
• Can learn to use the Alice interface in a
few class periods if you do a couple of
exercises at home

Installing Alice
• If you want to install Alice on you computer at home
– use the CD that comes with the textbook
• CD installation is straightforward
– download Alice from the web
• http://www.alice.org/downloads/authoringtool/
• file format is .zip
• must “unzip” file using a program such as winzip
• problems? post to newsgroup

Memory Management
• Alice automatically manages memory
• But, writing and testing an animation is an
intense load on the computing system
– a crash can occur.
• Best solution:
• Alice (the program) reminds you every so often
so save your work
• save your programs often!
• if working in lab when you logout the computer is
wiped -> save to your account or to a backup
system such as a memory stick

The Power of Alice
• Automatically keeps track of 3-D objects
– what objects are in the virtual world
– types of objects
– positions of objects in the world

Demo
• Starting Alice
• Loading a World
• Running A World
• Saving a World
• How to Exit

The World
• Alice Programs / Movies take place in a
virtual world
• When you start a new world in Alice you
select the background
•The world consists
of a sky and the ground
•Can’t be changed after
creating the world
•the world is not infinite
DEMO
(I don’t like roller
coasters any more)

Objects in Alice
• Objects already exist. Hundreds of them

Program an Object

Where Do Objects Come From?
• They are pre built
– creating 3D objects is another area of computing and graphic
design
• Sources of 3D objects
– the local gallery that comes with the software
– Alice web gallery
• How are objects added to the world?

Adding Objects
• Click on the green “Add Objects” button
• World expands and local gallery displayed

Adding Objects
• Local gallery divided into a directory based
on subject
• add instances of objects to world by
– dragging and dropping or
– click on object and select add instance option

Objects in the World
• Can have multiple instances of objects
from the same class in the World
– class: like a cookie cutter
– objects: like the cookies
star cookie cutter
star cookie class
star cookies
star cookie objects

penguin class penguin objects in a virtual world

• The Objects that are present in the current
world are listed in the Object Tree
• The top left panel in the Alice
programming environment
• Every world comes with a
light, a camera (point of
view for the movie when
played), and the ground

Object Dimensions
• Objects in Alice worlds are 3 dimensional
height width depth

Object Position
• Objects
– are positioned in 3-D space
– Have six degrees of freedom (directions of movement)

Objects “Know” Relative Directions
• Yellow box around
penguin is its
bounding box
• light blue line is
up/down
• pink line is
left/right
• dark blue line is
forward backward
• DEMO

Exercises
• if you want to work at home, install Alice on
your computer
• Complete Appendix A, Part 1, using Alice
– a walkthrough of using Alice
• Complete the tutorials that come with Alice

Starting Tutorials

Visual programming

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