CS320n Elements of Visual Programming

1
CS320n Elements of Visual Programming

• Introduction to Alice
• Mike Scott
• (Slides 1-1)

2
What We Will Do Today

• look at the Alice programming environment
• create some simple programs in Alice

3
What is Alice?

• Named in honor of Lewis Carrolls (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.)

4
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

5
Fundamental Tools

• All languages contain these elements
• list of instructions Pack lunch, pack snack,
  put homework in backpack.
• decision making If I didnt shave yesterday,
  shave today.
• repetition of behavior Do a load of laundry
  until there is no more dirty laundry.
• 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
• Generalization Solve many different problems
  with one set of instructions
• Compute a result How much is it going to cost
  to fill up my car with gas?

6
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

7
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

8
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

9
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

10
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

11
Demo

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

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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 consistsof a sky and the ground
• Cant be changed aftercreating the world
• the world is not infiniteDEMO(I dont like
  roller coasters any more)

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Objects in Alice

• Objects already exist. Hundreds of them

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Program an Object
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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?

16
Adding Objects

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

17
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

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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 cutterstar cookie class
star cookiesstar cookie objects
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Objects in the World
penguin class
penguin objects in a virtual world
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Objects in the 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 whenplayed), and the
  ground

21
Object Dimensions

• Objects in Alice worlds are 3 dimensional

height width depth
22
Object Position

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

23
Objects Know Relative Directions

• Yellow box aroundpenguin is itsbounding box
• light blue line isup/down
• pink line is left/right
• dark blue line isforward backward
• DEMO

24
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

25
Starting Tutorials