ref: df03eca7e7cbfadf1cf8c8c5a94390eaa5013a8b
dir: /appl/spree/other/tstboing.b/
implement Tst; include "sys.m"; sys: Sys; include "draw.m"; draw: Draw; Point, Rect: import draw; include "sh.m"; sh: Sh; Context: import Sh; include "math.m"; math: Math; ZERO: con 1e-6; stderr: ref Sys->FD; Tst: module { init: fn(nil: ref Draw->Context, argv: list of string); }; π: con Math->Pi; Maxδ: con π / 4.0; init(nil: ref Draw->Context, argv: list of string) { sys = load Sys Sys->PATH; stderr = sys->fildes(2); math = load Math Math->PATH; if (len argv != 9) { sys->fprint(stderr, "args?\n"); exit; } ar := argv2r(tl argv); br := argv2r(tl tl tl tl tl argv); a := Line.new(ar.min, ar.max); # ball b := Line.new(br.min, br.max); # bat (hit, hitp, s, t) := b.intersection(a.p, a.v); if (hit) { nv := boing(a.v, b); rl := ref Line(hitp, nv, 50.0); ballθ := a.θ(); batθ := b.θ(); φ := ballθ - batθ; δ: real; if (math->sin(φ) > 0.0) δ = (t / b.s) * Maxδ * 2.0 - Maxδ; else δ = (t / b.s) * -Maxδ * 2.0 + Maxδ; nl := Line.newpolar(rl.p, rl.θ() + δ, rl.s); sys->print("%s %s %s\n", p2s(rl.point(0.0)), p2s(rl.point(rl.s)), p2s(nl.point(nl.s))); } else sys->fprint(stderr, "no hit\n"); } argv2r(v: list of string): Rect { r: Rect; (r.min.x, v) = (int hd v, tl v); (r.min.y, v) = (int hd v, tl v); (r.max.x, v) = (int hd v, tl v); (r.max.y, v) = (int hd v, tl v); return r; } Line: adt { p, v: Realpoint; s: real; new: fn(p1, p2: Point): ref Line; hittest: fn(l: self ref Line, p: Point): (Realpoint, real, real); intersection: fn(b: self ref Line, p, v: Realpoint): (int, Realpoint, real, real); point: fn(b: self ref Line, s: real): Point; θ: fn(b: self ref Line): real; newpolar: fn(p: Realpoint, θ: real, s: real): ref Line; }; Realpoint: adt { x, y: real; }; Line.new(p1, p2: Point): ref Line { ln := ref Line; ln.p = (real p1.x, real p1.y); v := Realpoint(real (p2.x - p1.x), real (p2.y - p1.y)); ln.s = math->sqrt(v.x * v.x + v.y * v.y); if (ln.s > ZERO) ln.v = (v.x / ln.s, v.y / ln.s); else ln.v = (1.0, 0.0); return ln; } Line.newpolar(p: Realpoint, θ: real, s: real): ref Line { l := ref Line; l.p = p; l.s = s; l.v = (math->cos(θ), math->sin(θ)); return l; } Line.θ(l: self ref Line): real { return math->atan2(l.v.y, l.v.x); } # return normal from line, perpendicular distance from line and distance down line Line.hittest(l: self ref Line, ip: Point): (Realpoint, real, real) { p := Realpoint(real ip.x, real ip.y); v := Realpoint(-l.v.y, l.v.x); (nil, nil, perp, ldist) := l.intersection(p, v); return (v, perp, ldist); } Line.point(l: self ref Line, s: real): Point { return (int (l.p.x + s * l.v.x), int (l.p.y + s * l.v.y)); } # compute the intersection of lines a and b. # b is assumed to be fixed, and a is indefinitely long # but doesn't extend backwards from its starting point. # a is defined by the starting point p and the unit vector v. # return whether it hit, the point at which it hit if so, # the distance of the intersection point from p, # and the distance of the intersection point from b.p. Line.intersection(b: self ref Line, p, v: Realpoint): (int, Realpoint, real, real) { det := b.v.x * v.y - v.x * b.v.y; if (det > -ZERO && det < ZERO) return (0, (0.0, 0.0), 0.0, 0.0); y21 := b.p.y - p.y; x21 := b.p.x - p.x; s := (b.v.x * y21 - b.v.y * x21) / det; t := (v.x * y21 - v.y * x21) / det; if (s < 0.0) return (0, (0.0, 0.0), s, t); hit := t >= 0.0 && t <= b.s; hp: Realpoint; if (hit) hp = (p.x+v.x*s, p.y+v.y*s); return (hit, hp, s, t); } # bounce ball travelling in direction av off line b. # return the new unit vector. boing(av: Realpoint, b: ref Line): Realpoint { d := math->atan2(real b.v.y, real b.v.x) * 2.0 - math->atan2(av.y, av.x); return (math->cos(d), math->sin(d)); } p2s(p: Point): string { return string p.x + " " + string p.y; }