Interactive Systems
Class 9
Creature of the week
Outline
What you should know by now
On wagging tails
Notes on the assignment
Some big ideas – artificial life
Moving objects in the world, timers,
collision detection
What you should be able to do by now
Rotate an object
Co-ordinate between objects to start
rotations
Animate an avatar
Hints about wagging tails – problem!
 You need to attach the tail to an anchor object
which is can rotate around (like a ball and socket
joint)
 The problem is that once you join the tail to the
body, it no longer rotates around the ball and
socket
 We are looking into this to find a solution and will
let you know when we do.
 In the mean time if you want to keep working,
look into llSetLinkPrimitiveParams(tail_number,
[PRIM_ROTATION, r]);
Notes on the assignment
Remember you will be peer reviewing each other's
pets next week in the labs. This means two
things:
1. You have to have a pet ready to be reviewed. It
does NOT need to be finished, but it should be
a work in progress
2. You must attend the labs in weeks 10 /11to
take part in the peer review, or miss 25% of
your assignment mark.
 1st year: Fri 21st Nov 3.15 – 5.15pm
 2nd year: Tues 25th Nov 2.15 – 4.15pm
A tip
For the assignment, you are expected to
do something more than write a couple of
lines of code within a function or event.
You should be working on a more complex
program: putting the bits and pieces you
have learned in lab class into a coherent
whole
If this sounds hard, discuss it with the lab
helper this week
Interactive behaviour of the pet
40 – 49%. Poor. Pet has major bugs, or is
extremely derivative. Limited scripting skills
demonstrated (e.g. just basic text output)
 50 – 59% Adequate. Pet has at least one
interactive behaviour. It demonstrates that
basic scripting skills have been learned and
used to respond to user input (typed text, or
button clicking). Output could be text, sounds or
animations.
Interactive behaviour of the pet
60 – 69% Good. Pet demonstrates a couple of
interesting behaviours. It can respond to the
surroundings and other creatures as well as the
user.
70% + Excellent. Exhibit demonstrates a
complex behaviour which requires more
advanced scripting. For example, it could
execute a sequence of behaviour under script
control, or behave as a member of a flock.
Artificial Life
 “Artificial life (commonly Alife or alife) is a field
of study and an associated art form which
examine systems related to life, its processes,
and its evolution through simulations using
computer models, robotics, and biochemistry.[1]”
Wikipedia
 Strong alife: "life is a process which can be
abstracted away from any particular medium"
John von Neumann
 What do you think about this?
Artificial Life
“(the) law of ``uphill analysis and downhill
synthesis'' applies... it's easier to design a
mechanism from scratch to do something,
than to figure out just how nature has
contrived to do it; this suggests that maybe
the natural way isn't really insuperably
complicated.” Cosma Shalizi
Braitenburg’s Vehicles
An example of behaviour based robotics
 See http://www.amazon.co.uk/gp/reader/0262521121/ref=sib_dp_pt/2773507346-2749668#reader-page
A creature which is afraid of the light:
More light produces faster movement.
Less light produces slower movement.
Darkness produces standstill.
Braitenburg’s Vehicles - example
 “This run has three vehicles, each of a different type, and
two lamps. Green is the obsessive one. She
singlemindedly and frenetically searches for and
attempts to ram the nearest and brightest light source,
and has no regard for anything else (behaving like
Braitenberg's Vehicle 2b). Blue has more self-control
and more intelligence. She likes to find a cozy spot near
a lamp and settle down, but she will flee if a predator
comes too close. Red is the predator; Light doesn't
interest her, only the movement of possible prey.”
http://people.cs.uchicago.edu/~wiseman/v
ehicles/animation-1.mov
Boids
 An algorithm used for simulating flocking
behaviour
 Used in games and 3D animations
 http://www.red3d.com/cwr/boids/
 Complexity emerges from 3 simple rules:
Separation: steer to avoid crowding local flockmates
Alignment: steer towards the average heading of
local flockmates
Cohesion: steer to move toward the average position
of local flockmates
Scripting you will learn today
Cookie monster gets hungry again after a
bit
Cookie monster grazes for food
Cookie monster side-steps round
obstacles
Cookie monster mummy and daddy make
babies
Delaying hunger pangs
How would you stop the monster getting
hungry as soon as he has eaten?
Delaying hunger pangs
integer hungry = 0;
timer(){
llOwnerSay("Getting hungry again");
hungry =1;
}
eat(){
llOwnerSay("I found a cookie");
llSay(42, "eaten");
hungry = 0;
llOwnerSay("Burp. Not hungry anymore");
//set a timer so he doesn't get hungry for 30 seconds
llSetTimerEvent(15.0);
}
How would you make the cookie
monster graze?
Monster will sense a cookie and move
towards it. When close enough he will eat
it.
Need to use sensor, llTarget and
llMoveToTarget
Grazing solution part 1
moveToCookie(vector cookiePos){
llSetStatus(STATUS_PHYSICS, TRUE);
llSetStatus(STATUS_ROTATE_X |
STATUS_ROTATE_Y | STATUS_ROTATE_Z,
FALSE);
// Ask to be informed when we’re 0.5 metres
from cookie
targetID = llTarget(cookiePos, 0.5 );
//start moving to cookie
llMoveToTarget(cookiePos, 0.9);
}
Grazing solution part 2
sensor(integer num){
vector targetPos;
targetPos =llDetectedPos(0) + <1.0, 0.0, 0.0>;
if (hungry){
moveToCookie(targetPos);
}
else{
llOwnerSay("Quietly digesting");
}
}
Grazing solution part 3
at_target( integer number, vector targetpos, vector ourpos
)
{
llOwnerSay("We've arrived!");
eat();
// Stop moving towards the destination
llStopMoveToTarget();
// Stop notifications of being there or not
llTargetRemove(targetID);
// Become non-physical
llSetStatus(STATUS_PHYSICS, FALSE);
}
Side step to avoid obstacles
//we have detected that we have collided, so move out of the way
collision(integer num_detected){
llOwnerSay("Oi!");
vector pos = llGetPos() + <0.0, 2.0, 0.0>;
llSetStatus(STATUS_PHYSICS, TRUE);
llMoveToTarget(pos, 0.2);
}
Mating behaviour
//we have detected that we have collided, so move out of the way
collision(integer num_detected){
if (llDetectedName(0) == "CookieMonsterGreen"){
breed("green");
}
else{
llOwnerSay("Oi!");
vector pos = llGetPos() + <0.0, 2.0, 0.0>;
llSetStatus(STATUS_PHYSICS, TRUE);
llMoveToTarget(pos, 0.2);
}
}
Mating behaviour
//called under collision detection with another monster
breed(string name){
offset = <0.5, 0.0, 0.0>;
vector velocity = <0.0, 0.0, 0.0>;
llOwnerSay("Well, hey there gorgeous");
if (name == "green"){
llRezObject("babycookiemonster",
llGetPos() +offset, velocity, ZERO_ROTATION,
1);
}
}
Mating behaviour (attached to baby)
on_rez(integer startParam)
{
birth(startParam);
}
birth(integer colour){
//mum was blue, dad was green, I should be cyan
if (colour == 1){
llSetColor(<0.0, 1.0, 1.0>, ALL_SIDES);
llSetLinkColor(LINK_SET, <0.0, 1.0, 1.0>, ALL_SIDES);
}
Homework
Work on your pet so you have something
to show your reviewers next week
Finish off previous lab exercises (this will
give you practice at writing the kinds of
scripts you need for your pets)