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Structure of Artist Virtual Environments. Mark Green School of Creative Media. Introduction. We have examined some of the techniques for building virtual environments time to look at some real environments: how they are structured techniques used to construct them what we need to support
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Structure of Artist Virtual Environments Mark Green School of Creative Media
Introduction • We have examined some of the techniques for building virtual environments • time to look at some real environments: • how they are structured • techniques used to construct them • what we need to support • then look at narrative structure and some of the other things we need
Artistic Virtual Environments • Very few virtual environments are well documented, lack of good visual and written descriptions • without good documentation can’t analyze the techniques used, not enough information • start with one project: Art and Virtual Environments, Banff Canada, 1991-94
Art and Virtual Environments • Around a dozen pieces produced over a three year period • hardware: • SGI Onyx1 RE (4Mb texture, 64 Mb main memory, R4000 processors) • mainly HMD, some projection • Fastrak and Dataglove for input
Bar Code Hotel • Features: • non-standard device configurations • autonomous object behaviors • users suggest behaviors, don’t control detailed motion, commands like: chase, drift, wall flower and punch • richness comes from the interactions between multiple users
Archeology of a Mother TongueToni Dove and Michael Mackenzie • Takes place in a theatre, large screen projector, a guide runs the piece navigating with a Dataglove • approximately 40 minutes for the entire piece • strong emotional responses from the audience, not like a typical VR piece
Archeology of a Mother TongueToni Dove and Michael Mackenzie
Archeology of a Mother TongueToni Dove and Michael Mackenzie • Three main features: • strong visual effect • minimal interaction, mainly navigation • strong narrative component • the piece tells a story, the guide moves the audience between the different parts of the story
Narrative • Narrative structure consists of scenes and transitions • the story is told in the scenes, each scene contains part of the story • the transitions are used to move between scenes, change the setting for the next part of the story, usually short: 10 seconds
PlaceholderBrenda Laurel and Rachael Strickland • A shared environment, two participants • has a much looser narrative structure, more concentration on interaction • the interaction drives the story • intended to be an experience, participants take turns playing the four characters in the story
PlaceholderBrenda Laurel and Rachael Strickland • Features: • role playing, users take on characteristics of other characters, modify their view and behavior • voiceholders: ability to leave marks on the environment • interaction between participants • spatial sound
Voiceholders • Artifacts in environment, used to record user’s voice • user grabs an empty voiceholder to record a message • grab a full voiceholder to hear the message • build up narrative by leaving messages for future users
Scenes and Transitions • Three scenes: cave, waterfall and hoodoos • each scene has a different visual presentation and characteristics, not story driven • users control scene transitions by entering a portal to another scene • 10 second transition for user orientation
The Bush Soul • A more recent piece developed by Rebecca Allen at UCLA • under development for a number of years, with a good sized team • shown in 1998 and 1999 • PC based multi-screen system with joystick as the main input device
The Bush Soul • This piece has a linear narrative structure, the user visits four sites over a virtual day • environment populated by creatures • these creature are autonomous, they react to each other, the user and actions that occur in the environment • user can enter the body of one of the creatures
Summary • Features that should be supported • object behavior • autonomous • user controlled • non-standard device configurations • interaction • with user • between objects • between users
Summary • Features (continued): • visual richness • multiple media: graphics, sound, force, … • scenes and transitions, support for narrative structure • control of user • how they experience the environment • where they can move
More Behavior • The behavior we have done so far has been mechanical, it doesn’t appear intelligent • we will now look at ways of doing more intelligent behavior • what do we mean by intelligent behavior? • What a real organism might do? • Something that doesn’t look stupid?
More Behavior • The features of intelligent behavior: • goal directed • react to environment • avoid collisions or other accidents • social actions: move towards objects we like, away from objects we don’t like • do what we might do??
Goal Directed Behavior • Often over rated, many assume that all behaviors are goal directed • this makes the theory and programming much easier • we can select the goals, and then produce the appropriate actions • can string goals together to achieve larger goals
Goal Directed Behavior • Goals can have hierarchies • short term goals are short lived, solve an immediate problem • longer term goals take longer to reach, require more planning and time • long term goals usually divided into a sequence of shorter term goals
Goal Directed Behavior • Many AI and Alife techniques have been developed based on this approach • lots of algorithms to draw on • But, are we really goal directed? • Some of the time we definitely are, when we have a problem to solve, or something that needs to be done
Goal Directed Behavior • Other time assigning goals to our actions is quite difficult: • watching cartoons on TV • going for a walk • browsing in a store (or the web) • we can try to assign goals to these activities, but they sound more like excuses
Goal Directed Behavior • Quite often we assign goals to people’s actions when we really have no idea of what they are doing • this makes life seem more rational • Example, a large crowd of people walking, we assume they all know where they are going, this may not be the case
Goal Directed Behavior • Doing good goal directed behavior is quite hard, often looks more like a robot than a living object • it’s not clear that it buys us anything, better off spending our time developing other behaviors • if it looks like it could have a goal, its probably good enough
Realistic Behavior • Actions should look like they have a purpose, object doesn’t do anything stupid • we want our objects to move around the environment: • mainly travel in a straight line, so they look like they know where they are going • avoid running into other objects • start by looking at a simple object, mover
Mover • The mover moves in a simple environment: • floor • four walls • both the floor and walls are made from the same plane • want to make the mover look like it has a purpose, not just a random walk • the mover is a small cube
Mover • Two observations: • we walk in the direction we are facing • we walk in straight lines as long as possible • in each tick the mover moves a small amount in the direction its facing • the push action does this: push distance; • to change direction use rotz
Mover Direction of motion Mover
Mover • When we reach an obstacle (a wall) we need to do something • one solution is to turn so we are no longer facing the obstacle • two questions: • how do we know when we are about to hit something? • How much do we turn?
Mover • The hit action can assist with obstacle avoidance • hit shoots a ray, given a starting point and direction, returns any object hit and the distance to the object: hit x, y, z, rx, ry, rz, obj; • first three parameters are start of ray, next three are the ray direction
Mover • The last parameter is a variable, name of hit object stored in this variable • the variable “distance” is set to the distance to the object • what direction and position should we use? • The position and direction of the object! • This information is stored in a set of variables
Mover • Object position: Locx, Locy, Locz • Object direction: Anglex, Angley, Anglez • hit functions as eyes, looks to see what is in front of the object • since the environment is enclosed, we will always hit something, so should we always turn? • Only if the obstacle is close
Mover • The environment is 12x12, we are moving at 6 units/second • start avoiding collision when we are 2 units from obstacle • the basic motion is done in the tick event handler • the turn event handler is used for basic obstacle avoidance
Mover on tick eval v = 6*dt; push v; hit Locx, Locy, Locz, Anglex, Angley, Anglez, obj; select obj; if distance < 2; trigger “mover”, “turn”; endif end
Mover • Now we need to turn • the basic idea is to turn a bit (0.4 radian), and see if we are still going to collide • this is repeated until the collision is avoided • if for some reason the mover gets too close to the obstacle (less than 0.2 units) we have an emergency action, the back event handler
Mover • In the back event handler we move back two steps and then make a large turn (1.5 radians, about 90 degrees) • we then continue the motion • this should avoid any potential disaster
Mover on turn spinz 0.4; hit Locx, Locy, Locz, Anglex, Angley, Anglez, obj; select obj; set flag 0; if distance < 2 ; set flag, 1; endif select flag; triggerif distance < 0.2, me, “back”; triggerif distance > 0.2, me, “turn”; end on back eval dx = -2*v; push dx; spinz -1.5; end
Mover • What we’ve done so far gives us basically circular motion • the mover travels in a circle just inside the walls • this looks kind of stupid • periodically change the objects direction, a random change in direction, every 4 to 10 seconds
Mover on change random dz, 1.20, 3.14; spinz dz; random t, 4, 10; triggerAt “mover”, “change”, t; end on first translate 0, 0, 0.15; triggerAt “mover”, “change”, 5; end
Mover • Gives relatively good basic motion • can introduce a number of obstacles into the environment, a set of cubes • the mover can successfully avoid them • this gives us one motion unit, later we will add more behavior to the mover
The Thing • The mover can move around the environment, but it only reacts to obstacles • the thing is a plant-like creature that reacts to the user • the thing normally bends back and forth at a fairly slow rate (think about a plant slowly blowing in the wind)
