/** * Non-orthogonal Collision with Multiple Ground Segments  * by Ira Greenberg.  *  * Based on Keith Peter's Solution in * Foundation Actionscript Animation: Making Things Move! */Orb orb;PVector velocity;float gravity = .05, damping = 0.8;int segments = 40;Ground[] ground = new Ground[segments];float[] peakHeights = new float[segments+1];void setup(){  size(640, 200);  smooth();  orb = new Orb(50, 50, 3);  velocity = new PVector(.5, 0);  // Calculate ground peak heights   for (int i=0; i<peakHeights.length; i++){    peakHeights[i] = random(height-40, height-30);  }  /* Float value required for segment width (segs)   calculations so the ground spans the entire    display window, regardless of segment number. */  float segs = segments;  for (int i=0; i<segments; i++){    ground[i]  = new Ground(width/segs*i, peakHeights[i],    width/segs*(i+1), peakHeights[i+1]);  }}void draw(){  // Background  noStroke();  fill(0, 15);  rect(0, 0, width, height);  // Move orb  orb.x += velocity.x;  velocity.y += gravity;  orb.y += velocity.y;  // Draw ground  fill(127);  beginShape();  for (int i=0; i<segments; i++){    vertex(ground[i].x1, ground[i].y1);    vertex(ground[i].x2, ground[i].y2);  }  vertex(ground[segments-1].x2, height);  vertex(ground[0].x1, height);  endShape(CLOSE);  // Draw orb  noStroke();  fill(200);  ellipse(orb.x, orb.y, orb.r*2, orb.r*2);  // Collision detection  checkWallCollision();  for (int i=0; i<segments; i++){    checkGroundCollision(ground[i]);  }}void checkWallCollision(){  if (orb.x > width-orb.r){    orb.x = width-orb.r;    velocity.x *= -1;    velocity.x *= damping;  }   else if (orb.x < orb.r){    orb.x = orb.r;    velocity.x *= -1;    velocity.x *= damping;  }}void checkGroundCollision(Ground groundSegment) {  // Get difference between orb and ground  float deltaX = orb.x - groundSegment.x;  float deltaY = orb.y - groundSegment.y;  // Precalculate trig values  float cosine = cos(groundSegment.rot);  float sine = sin(groundSegment.rot);  /* Rotate ground and velocity to allow    orthogonal collision calculations */  float groundXTemp = cosine * deltaX + sine * deltaY;  float groundYTemp = cosine * deltaY - sine * deltaX;  float velocityXTemp = cosine * velocity.x + sine * velocity.y;  float velocityYTemp = cosine * velocity.y - sine * velocity.x;  /* Ground collision - check for surface    collision and also that orb is within    left/rights bounds of ground segment */  if (groundYTemp > -orb.r &&    orb.x > groundSegment.x1 &&    orb.x < groundSegment.x2 ){    // keep orb from going into ground    groundYTemp = -orb.r;    // bounce and slow down orb    velocityYTemp *= -1.0;    velocityYTemp *= damping;  }  // Reset ground, velocity and orb  deltaX = cosine * groundXTemp - sine * groundYTemp;  deltaY = cosine * groundYTemp + sine * groundXTemp;  velocity.x = cosine * velocityXTemp - sine * velocityYTemp;  velocity.y = cosine * velocityYTemp + sine * velocityXTemp;  orb.x = groundSegment.x + deltaX;  orb.y = groundSegment.y + deltaY;}