ray.js

class Ray {
    constructor(pos, angle) {
        this.pos = pos;
        this.dir = p5.Vector.fromAngle(angle);
    }

    lookAt(x, y) {
        this.dir.x = x - this.pos.x;
        this.dir.y = y - this.pos.y;
        this.dir.normalize();
    }

    setPos(pos) {
        this.pos = pos;
    }

    cast(wall) {
        const x1 = wall.a.x;
        const y1 = wall.a.y;
        const x2 = wall.b.x;
        const y2 = wall.b.y;

        const x3 = this.pos.x;
        const y3 = this.pos.y;
        const x4 = this.pos.x + this.dir.x;
        const y4 = this.pos.y + this.dir.y;

        const den = (x1 - x2) * (y3 - y4) - (y1 - y2) * (x3 - x4);

        if(den == 0) return;

        const t = ( (x1 - x3) * (y3 - y4) - (y1 - y3) * (x3 - x4) ) / den;
        const u = - ( (x1 - x2) * (y1 - y3) - (y1 - y2) * (x1 - x3) ) / den;

        if(t >= 0 && t <= 1 && u >= 0) {
            return {
                'x': x1 + t * (x2 - x1),
                'y': y1 + t * (y2 - y1),
                'u': u
            };
        } else {
            return;
        }
    }

    show() {
        stroke(255, 0, 0, 100);
        push();
        translate(this.pos.x, this.pos.y);
        line(0, 0, this.dir.x * 10, this.dir.y * 10);
        pop();
    }
}