Introduction to programming - class 6
- 1. Introduction to Programming Class 6 Paul Brebner
- 2. Exercise • Create a cannon trajectory game – Place a cannon at lower left of screen, with a target on lower right. – Set initial cannon angle (0-90 degrees, 0 is horizontal, 90 is vertical), and velocity, and cannon ball location (x and y, same as cannon). – Calculate velocity of the cannon ball, vx and vy, initially: • float vx = velocity * cos(radians(angle)); • float vy = velocity * sin(radians(angle)); – Each frame, change x and y position (and draw ball) and vy as follows: • x += vx; // add vx to get next cannon ball x position • y -= vy; // subtract vy to get next cannon ball y position • vy -= g; // g is gravity acting down, try 1 – Remember that in processing x increases from 0 to width, and y from 0 to height (starting at top left, so increases as ball goes down!) – Use frameRate(1) (or slower) to make debugging easier – How will you change the angle and velocity? How will you fire? How will you check if the ball hits the target? What happens when it hits? – Can you put another cannon on the right and make the game 2 player? – Can you work out how load images for the cannon, ball, target, explosion etc? – Next page is a simple online example
- 4. Example program structure, add detail to TODOs // global variables for cannon and cannon ball position and velocity go here ... TODO boolean cannonFired = false; // true after cannon fired until ball lands void setup() // set size, background (sky colour), cannon position, and frame rate { TODO } void draw() // everything done once per frame { // draw cannon TODO if (cannonFired) { // move and draw the ball until it hits the ground again, then set cannonFired to false TODO } else { // change angle and velocity and firing of cannon, set cannonFired to true and cannon ball x and y to cannon location TODO } }