DIESEL

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Multimedia Authoring COM315
Lecture 4 Algorithm development Overview of lingo
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Algorithm Development
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Algorithm Development

• What is an algorithm?
• Programming languages for computers works in
  sequential steps unless told to branch off or
  repeat something.
• Tasks must be analysed with this in mind. This
  development process is called algorithmic
  thinking.

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Pseudo Code

• Algorithm development is done in Pseudo Code,
  (Almost human language)
• This process should precede all but the most
  trivial programming operations.
• Lecture focuses on algorithm development
• Some Lingo conventions used to help transition to
  real code.

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Where do I start?

• The most common question in program
• development is Where do I start?. The
• answer is
• State your assumptions.
• Break your task down into smaller tasks.
• Formulate step by step instructions to carry out
  each of the smaller tasks.

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Programming example

• Task
• Give instructions for making and serving coffee
  while reading the paper before breakfast.

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Assumptions

• Assumptions
• Instructions are for a machine that has the
  physical abilities of a human but is as literal
  minded as a computer.
• So, it can pick up a coffee pot but will have to
• be told exactly what to do and when to do it.

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Task Decomposition

• There are two main parts preparing the coffee
• and reading the paper.
• Initial algorithm
• Prepare coffee
• Read paper
• Proceed using stepwise refinement

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Stepwise refinement

• Our initial twostep algorithm can first be
• broken into three steps.
• Make coffee
• Serve coffee
• Read paper

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Stepwise refinement

• What is involved in making the coffee? Assume a
  filter
• coffee maker and fresh beans.
• Put new filter in coffee maker
• Grind beans
• Put grounds in filter
• Boil water
• Pour boiling water over grounds
• Let drip
• Serve coffee
• Read paper

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Procedures Handlers

• Algorithm description soon becomes a long and
  confusing list of instructions.
• Programming languages allow you to hide detail by
  declaring procedures or handlers (Lingo).
• Create handler called MakeCoffee

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Handlers

• MakeCoffee
• Serve coffee
• Read paper
• MakeCoffee step closer to Lingo code format

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on MakeCoffee Handler

• on MakeCoffee
• Put new filter in coffee maker
• Grind beans
• Put grounds in filter
• Boil water
• Pour boiling water over grounds
• Let drip
• end MakeCoffee

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Program execution
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Comment conventions

• Add comments
• Improves readability later understanding
• Ignored by the machine but help make the
  algorithm intelligible to humans.
• --This is a comment in Lingo.
• --Lines beginning "--" ignored by the machine.

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Variables

• To date we have only organised the instructions
  in
• program development. We need to organise
• information as well.
• E.g. Specify how much milk and sugar to serve
• with the coffee?
• We will use the construct called a variable.

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Variables

• A variable is simply a container that holds a
• value we specify and should have meaningful
• names.
• Define two variables
• NumberOfSpoons
• TakesMilk

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ServeCoffee handler
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Conditional action

• IF ltconditiongt THEN
• Action(s)
• END IF
• If the condition is not met, the action(s) are
  not
• performed. Program moves on to the next
• instruction in the sequence.
• Known as a Branch.

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Variables values

• Variables have to be assigned values before
• they can be used.
• This will be done in the main program.

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Variables values
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Local global variables

• Lingo would not know about these variables in the
  main program as they are introduced in the
  handler ServeCoffee.
• Variables which will be used only within a
  handler are called local
• Variables which can be used by other handlers (or
  movies) are called global.
• Globals have to be declared as such and given a
  value before being used.

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Global variables
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Variables

• Suppose we wish to serve coffee to more than
• one person. We can now make further use of
• the variables by giving them different values for
  
• the second serving.
• The algorithm for the main program now
• becomes

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Variables
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Arguments

• Once we start using variables and handlers
• more than once, we run the risk of having to
• keep track of lots of values as the main
• program grows longer. It would be simpler if our
• procedures could be supplied with values as
• they were called.

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Arguments

• For example, we could then call ServeCoffee
• like this
• ServeCoffee(2, yes)
• Which means two spoons of sugar with milk.

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Arguments

• This is a lot more concise and readable than
• set NumberOfSpoons 2 --two sugars
• set TakesMilk yes --and milk
• ServeCoffee

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Arguments

• ServeCoffee must be rewritten to know that it
• will receive the information in this form.
• In Lingo, variables passed to a handler are
• called parameter variables or arguments.

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Arguments
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Concise programs
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Summary

• Algorithms
• stating assumptions
• decomposition
• stepwise refinement
• execution flow
• comments

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Summary

• Procedures
• handlers (defining a procedure)
• parameters and arguments

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Summary

• Variables
• declaring a variable
• initialising a variable
• assigning a value to a variable

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Summary

• These steps are the basis of successful
• programming. The more you use them, the
• easier you will find them to understand.

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Introduction to Lingo

• Lingo is Director's programming Language
• Allows advanced interactivity in a Movie
• Reasonably straightforward to use
• But it is a programming language !!!!

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Lingo Events

• All Lingo commands get executed by the start
• of an event Event handler
• on mouseup
• on mousedown

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Structure of Lingo Command

• On MouseDown
• Go to Frame 1
• End
• On --- (Signals an event)
• MouseDown (The event)
• Go to (The command)
• Frame 1 (The expression)
• End

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Handlers

• Handlers are several lingo commands put
• together to perform a task
• On MouseDown
• Go to Frame 1
• End

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Types of Lingo scripts

• Primary event handlers
• Sprite scripts (Behavior)
• Cast scripts
• Frame scripts
• Movie scripts

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Handling Hierarchy

• Primary event handler
• Sprite Script
• Cast member Script
• Frame Script
• Movie Script

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Handling Hierarchy
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Lingo Grammar
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Lingo Grammar
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Lingo Grammar
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Sprite properties
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Lingo sprite properties
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Rollover Example
Member specifies a sprite's cast member and
cast
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Lingo condition statements
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Draggable Behavior
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Behaviors

• A set of Lingo commands that controls the
• action of a Sprite. Director comes with some
• Pre made behaviors that your can use as-is, or
• edit to fit your needs.
• Example Hold on current frame

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Questions on project

• Questions on group project

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Team presentations

• There will be a team presentation of completed
  work on Week 7, 06/11/08 _at_ 9.15 in MBO10
• 15 Minutes per team, 10 minutes presentation, 5
  minutes questions
• Each team member must attend, participate and
  present!
• All class members must attend all sessions!

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Schedule

• Team 1 MC Building 9.15
• Team 2 ME Building 9.30
• Team 3 MR Creche 9.45
• Team 4 MM Library 10.00
• Team 5 MI - Aberfoyle House 10.15
• Team 6 MQ Foyle Arts 10.30
• Team 7 MS - ISRC Research building 10.45

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Assignment 1 Mark Allocation
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Assignment 1 Deliverables

• Digital copy of storyboard/planning process in
  powerpoint CDROM/Building (on CDROM)
• This includes concept sketches/plans/photos
• Macromedia Director CDROM presentation
• Director source code
• Bio/images of Team Avatars
• Images/video of construction process of building
  in Second Life
• Video of walkthrough of completed building
• Copy of group presentation from Week 7

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Submission Deadlines

• Assignment 1 31/10/08 (Week 6)
• Assignment 2 12/12/08 (Week 12)
• Assignment 3 11/12/08 (Week 12)

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Lab week 4

• ½ Hour Second Life
• Director

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Multimedia Authoring COM315
Lecture 4 Algorithm development Overview of lingo