Objects and Properties

1. Alice Objects and Properties

2. Objects in Alice • Objects already exist. Hundreds of them

3. Objects • In the demo worlds, the octopus and skater are objects. • An "object" is • anything that can be identified as unique from other things • How is an object identified as unique? • has a name • has properties: • width, height, color, location, age, ss#, id# • has a purpose: • associated actions it can perform • tasks it can carry out

4. Objects in a Virtual World • In Alice, each 3D model is a class of objects • each object of the class has a unique name • mummy, mummy1, mummy2 • has color(s) • pink, white, grey, black, blue, ….

5. 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

6. Objects in the World penguin class penguin objects in a virtual world

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

8. Objects “Know” Relative Directions • Yellow box around penguin is itsbounding box • light blue line is up/down • pink line is left/right • dark blue line isforward backward • DEMO

9. Galleries of 3D Objects • Sources of 3D objects • the local gallery shipped with the software • Alice web gallery

10. Objects in a Virtual World • In Alice, each 3D model is a class of objects • class: penguin • objects: penguin, penguin2, penguin3

11. Problem • Suppose I want a Penguin to disappear from the screen during the animation.

12. Solution • The solution is to change the opacity (degree of transparency) while the animation is running. • Opacity is a property of the penguin object. • All objects in Alice have properties, which include (among others): • location (x, y, z) • orientation • color • opacity • vehicle

13. Changing Properties of Objects • Properties of Object can be changed • Location can be changed by clicking and moving object • Orientation can be changed in the “Add Objects” View • Other properties, such as color, can be changed in the properties window when the object is selected

14. Object Parts • Objects may be composed of parts • which may in turn be composed of parts • the whole object may be told to do something or an individual part

15. Object Parts • Objects may be composed of parts

16. 3D objects • A 3D object has • 3 dimensions • height, width, depth • 6 degrees of freedom (directions of movement)

17. Distance • object’s distance from each other are based on the distance between their center points • may look like objects are zero distance away, but actually centers still some positive distance away

18. Position in the World • The world in an Alice program models a 3D space • every object in the world has a positionx, y, z, coordinate relative to the center of the world • ground starts at center of world • axes (green = up, red = right, blue = forward)

19. Vehicles • Each object has a vehicle property • Initially the world is the vehicle for objects • can change this by altering the vehicle property for an object • Give the snowman an instrument • Change “ahem” to “toot” • What happens when movie played?

20. Alter the Vehicle Property Select sax from object tree Select properties tab Change vehicle from world to snowman

21. Assignment • Read Tutorial03 • Know what an object is instance of • Know how to use the properties • Read Tips & Techniques 2 • Orientation and Movement Instructions

22. Lab 03 • 3a) Penguin • 3b) Tortoise and the cookie • 3c) Mana and the magnet