ru:: ellipse platforms

rogueviz/ru/classes.cpp

@@ -484,6 +484,16 @@ struct pendulum_platform : public moving_platform {
   string get_help() override { return "These pendulum platforms go back and forth between two locations, taking the shortest path possible."; }
   };
 
+struct ellipse_platform : public moving_platform {
+  xy a, b;
+  ld ratio, period, shift;
+  vector<hyperpoint> points;
+  vector<ld> lengthsum;
+  xy location_at(ld t) override;
+  string get_name() override { return "ellipse platform"; }
+  string get_help() override { return "These platforms go in an ellipse."; }
+  };
+
 struct rope_platform : public moving_platform {
   ld period, shift, dist, max_swing;
   xy location_at(ld t) override;

rogueviz/ru/entity.cpp

@@ -623,6 +623,36 @@ xy pendulum_platform::location_at(ld t) {
   return from_hyper(rgpushxto0(h1) * rspintox(gpushxto0(h1) * h2) * xpush0(x));
   }
 
+xy ellipse_platform::location_at(ld t) {
+  if(points.empty()) {
+    auto h1 = to_hyper(a);
+    auto h2 = to_hyper(b);
+    auto m = mid(h1, h2);
+    ld wanted = hdist(h1, h2) * ratio;
+    for(int it=0; it<360; it++) {
+      auto p = [&] (ld x) { return rgpushxto0(m) * spin(it*1._deg) * xpush0(x); };
+      ld x = binsearch(0, 5, [&] (ld x) { auto px = p(x); return hdist(h1, px) + hdist(h2, px) >= wanted; });
+      points.push_back(p(x));
+      }
+    int N = isize(points);
+    points.push_back(points[0]);
+    ld ls = 0;
+    for(int i=0; i<N; i++) {
+      lengthsum.push_back(ls);
+      ls += hdist(points[i], points[i+1]);
+      }
+    lengthsum.push_back(ls);
+    }
+  ld our_t = t / (period * game_fps);
+  our_t -= floor(our_t);
+  our_t *= lengthsum.back();
+  auto it = lower_bound(lengthsum.begin(), lengthsum.end(), our_t);
+  auto index = it - lengthsum.begin();
+  auto& h1 = points[index-1];
+  auto& h2 = points[index];
+  return from_hyper(rgpushxto0(h1) * rspintox(gpushxto0(h1) * h2) * xpush0(our_t - lengthsum[index-1]));
+  }
+
 void moving_platform::draw() {
   double d = get_scale();
   auto wi = width();

rogueviz/ru/load-world.cpp

@@ -321,6 +321,11 @@ void load_room(fhstream& f, cell *c) {
         b->a = get_xy(); b->b = get_xy(); b->period = get_ld(); b->shift = get_ld();
         r.entities.emplace_back(std::move(b));
         }
+      else if(cap == "ELLIPSE") {
+        auto b = std::make_unique<ellipse_platform>();
+        b->a = get_xy(); b->b = get_xy(); b->period = get_ld(); b->shift = get_ld(); b->ratio = get_ld();
+        r.entities.emplace_back(std::move(b));
+        }
       else if(cap == "HINT") {
         auto b = std::make_unique<hint>();
         b->respawn = get_xy(); b->size = get_xy();