Tips & Techniques 6 Random Numbers and Random Motion Alice

Random Numbers Random numbers are used in certain kinds of computer programs Examples: security for web applications encryption for satellite transmissions gaming programs scientific simulations In this session, we will look at examples of how to use random numbers in animations

Built-in functions Alice provides World-level built-in functions for generating random numbers.

Demo Ch06Lec3PenguinRandomMoves Concepts illustrated in this example The random number function returns a floating point value between 0 and 1. A different range of values can be obtained by using the minimum and maximum parameters. The integer only option allows selection of either floating point or whole numbers.

Random 3D Motion In the previous example, the penguin moves in only one direction. In some animations, we want an object to move to a random location in 3D. We call this random 3D motion. For example, the goldfish in this world is to swim in a random motion, where the fish can move in any direction.

Six possible directions Of course, six move directions are possible forward, backward, left, right, up, down In this example, we can eliminate backward because goldfish do not swim backward. To simplify the code, we can take advantage of negative numbers. For example, this instruction actually moves the goldfish right:

Storyboard Only three move instructions are needed: up (will move down if the random number is negative) left (will move right if random number is negative) forward (no backward motion) Two parameters (min, max) will be used to restrict the motion of the fish to a nearby location-- to look like swimming. randomMotion Parameters: min, max Do together fish moves up a random number distance fish moves left a random number distance fish moves forward a random number distance

Demo Ch06Lec3GoldfishRandom3DMotion Concepts illustrated in this example A random movement in 3D space is accomplished by three simultaneous move instructions. In this example, the minimum distance of the move forward instruction is 0 (the goldfish always moves forward). To call the randomMotion method, min and max values are sent as arguments to the parameters

Assignment Read Tips & Techniques 6, Random Numbers and Random Motion