Functions and Visual Effects

1
Functions and Visual Effects

• Chapter 6 Part 3

2
Built-in Functions

• We have been using built-in functions so far

3
How a Function Works

• A function
• Receives value(s) as arguments in parameters
• Performs computations on the value(s)
• Returns (sends back) a value

4
Types of Functions

• The function type depends on the type of value it
  returns
• Examples
• Number
• Specific object
• Boolean (true or false)
• Color
• Other property values

5
Create Function

• Click on create new function in class or world
  you want it to be in
• Name function and choose type of function
• A blank function will be created with return
  statement
• Value will be returned when function is done
• Place value you want returned in return statement

6
Function Window

• Since no action is performed in a function all
  instructions will be performed in sequential
  order
• No need for Do in order and Do together
• All will be Do in order
• Notice that you can place
• return elsewhere in function

7
Calorie Example

• A high school jock wants to know how many
  calories a cookie has
• He asks a lunch lady
• She consults the newly created calorie function
• 1 meter wide cookie 1000 calories

Number Function calories Parameter food Local
Number variable numCalories If food
cookie numCalories cookies width
1000 Return numCalories
8
Algorithm Translated to Alice

• My first method has jock ask lunch lady for the
  calories in the cookie
• The lunch lady checks how many calories with the
  calorie function and answers with the amount of
  calories

9
Visual Effects and Animation

• Billboards
• Fog
• Vehicles
• Pose
• Programming the Camera
• Creating Dummy Objects

10
Billboards

• Graphical images that have been inserted into the
  world
• Can insert images that are JPEG, GIF, TIF
• Known as Billboard
• Images are flat, 2D with height and widthno
  depth
• Can be used as backgrounds or scenery or used to
  giveinfo to the viewer!

11
Information Billboard

• Can be used as sign for instructions

12
Creating Billboard

• Can import images using Make Billboard
• In File menu

13
Fog

• Alice can give a look of mist to the world
• The entire world becomes less visible

14
Vehicle Property

• To have two objects move as one
• One object will be carried by another object
• Ex person on horse
• Horse is vehicle for person
• Choose properties tab
• In property of object being carried
• In vehicle choose object doing carrying

15
Pose

• Once an object has been put into a position or
  pose, the pose can be restored during an
  animation
• Pose is a property of an object
• setPose is a method of an object

16
Programming the Camera

• Camera can be programmed just like other objects
• All the same primitive methods and functions are
  available for it
• Point at, Move, Turn, etc.
• Camera can also be a vehicle for other objects

17
Creating Dummy Objects

• Dummy objects are invisible objects that are
  placed in the world
• Camera then moves to the invisible object toget
  different perspectives

18
Homework

• Read chapter 6 sections 6, 8, 9
• Do tutorial 6 and 7
• Do lab exercises
• Answer questions in handout
• Due one week after assigned with 1 week grace