Non Orthogonal Reflection
This is a port by David Blitz of the "Reflection 1" example from processing.org/examples
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//Position of left hand side of floor
let base1;
//Position of right hand side of floor
let base2;
//Length of floor
//let baseLength;
// Variables related to moving ball
let position;
let velocity;
let r = 6;
let speed = 3.5;
function setup() {
createCanvas(710, 400);
fill(128);
base1 = createVector(0, height - 150);
base2 = createVector(width, height);
//createGround();
//start ellipse at middle top of screen
position = createVector(width / 2, 0);
//calculate initial random velocity
velocity = p5.Vector.random2D();
velocity.mult(speed);
}
function draw() {
//draw background
fill(0, 12);
noStroke();
rect(0, 0, width, height);
//draw base
fill(200);
quad(base1.x, base1.y, base2.x, base2.y, base2.x, height, 0, height);
//calculate base top normal
let baseDelta = p5.Vector.sub(base2, base1);
baseDelta.normalize();
let normal = createVector(-baseDelta.y, baseDelta.x);
let intercept = p5.Vector.dot(base1, normal);
//draw ellipse
noStroke();
fill(255);
ellipse(position.x, position.y, r * 2, r * 2);
//move ellipse
position.add(velocity);
//normalized incidence vector
incidence = p5.Vector.mult(velocity, -1);
incidence.normalize();
// detect and handle collision with base
if (p5.Vector.dot(normal, position) > intercept) {
//calculate dot product of incident vector and base top
let dot = incidence.dot(normal);
//calculate reflection vector
//assign reflection vector to direction vector
velocity.set(
2 * normal.x * dot - incidence.x,
2 * normal.y * dot - incidence.y,
0
);
velocity.mult(speed);
// draw base top normal at collision point
stroke(255, 128, 0);
line(
position.x,
position.y,
position.x - normal.x * 100,
position.y - normal.y * 100
);
}
//}
// detect boundary collision
// right
if (position.x > width - r) {
position.x = width - r;
velocity.x *= -1;
}
// left
if (position.x < r) {
position.x = r;
velocity.x *= -1;
}
// top
if (position.y < r) {
position.y = r;
velocity.y *= -1;
//randomize base top
base1.y = random(height - 100, height);
base2.y = random(height - 100, height);
}
}
