gdc09 minipong

MiniGamesRebuilding Three Classics

Joe LinhoffEugene JarvisDarren Torpey

Pong, 1972

Goals

Not to recreate "Pong" -- get an emulator lots of MUCH easier ways to do this that will turn

out MUCH better with MUCH less time Program a Pong-like game from scratch Learn game development

programming game design process

Why Pong

First game games must keep score, start and end first with score, sound

Static fixed number of game objects

Simple

Game Development

Process workflow

Design what are you trying to do

Development tools and language build an exe

Game development techniques solutions to the problem space

1000 Features (handout)unique value 0..1000

possible feature for your game -- focus on what you see, hear, and how to get it on the screen

Tennis

78'-39..39 in X

27'-14..14 in Z

X

Z

Camera is above, looking down

paddlesball

Teaching Goallead students through first iteration

do brainstorm and design

1000 features handout

cover 000ZY coordinates

'draw' the camera draw the court exit cleanly

notes treat camera, matrix

as black box code adventurous students

can dig in focus on drawing

game objects

Game Loop update (voluntary)

move player paddles move ball

collide (involuntary) ball versus paddles ball versus court player versus court

draw draw court draw ball draw paddles draw score (HUD)

update performs voluntary

movement collision

handles involuntary movement

Velocities

variable frame rates float qeTimeFrame()

returns seconds since engine start / restart

keep track of the time since the last update

use Euler integration

// JFL 25 Jan 09class Ball : public qe {public: chr name[16]; // name float timeOfLastUpdate; // in seconds float xyz[3]; // current float vel[3]; // velocity Ball(chr *name); // constructor int update(); // update function int draw(); // draw function}; // class Ball

// update, move the ballfloat t;

// find time since last updatet=this->timeOfLastUpdate;this->timeOfLastUpdate=qeTimeFrame();t=this->timeOfLastUpdate-t; // delta

// xyz += vel*tthis->xyz[0]+=this->vel[0]*t;this->xyz[1]+=this->vel[1]*t;this->xyz[2]+=this->vel[2]*t;

Collisions

simplifications move, then collide

non-moving objects don't worry about

resolution order run through once

guarantee after detection, move

objects out of that collision (may be in another -- too bad)

end up in valid world position

no movement after collision resolution

Collisions ball v world

if over right or left score point, re-serve

if over top or bottom set to top or bottom reflect (flip z vel)

paddle v world make sure player

stays on the court ball v paddles

test against near edge of paddle set to near edge bounce (flip x vel) add English (later)

improvements preserve distance

when colliding don't just set to

collision edge reflect at collision point

does order matter? theoretically unlikely

fast balls could run through the

paddle depends on paddle

size and ball speed really need to handle

moving collisions

Draw simple filled rectangle

glColor3f(1,1,1); glPolygonMode(GL_FRONT,GL_FILL); // draw filled polygons glBegin(GL_QUADS); // draw quads counter-clockwise from camera's view glVertex3f(-1,0,-3); glVertex3f(-1,0,3); glVertex3f(2,0,3); glVertex3f(2,0,-3); glEnd();