Converted vision to interpolating angle based on capture timestamp.

Change-Id: I4885eb7eb1254af7266a5bd4c91d5d1b14b09eb2
diff --git a/y2016/vision/target_receiver.cc b/y2016/vision/target_receiver.cc
index b51e4ed..07c5ea0 100644
--- a/y2016/vision/target_receiver.cc
+++ b/y2016/vision/target_receiver.cc
@@ -19,7 +19,8 @@
 namespace y2016 {
 namespace vision {
 
-::aos::vision::Vector<2> CreateCenterFromTarget(double lx, double ly, double rx, double ry) {
+::aos::vision::Vector<2> CreateCenterFromTarget(double lx, double ly, double rx,
+                                                double ry) {
   return ::aos::vision::Vector<2>((lx + rx) / 2.0, (ly + ry) / 2.0);
 }
 
@@ -77,15 +78,16 @@
   double good_ang = min_angle;
   double min_ang_err = -1.0;
   int right_index = -1;
-  // Now pick the bottom edge angle from the right that lines up best with the left.
+  // Now pick the bottom edge angle from the right that lines up best with the
+  // left.
   for (int j = 0; j < right_target.target_size(); j++) {
     double wid2 = TargetWidth(right_target.target(j).left_corner_x(),
-                                right_target.target(j).left_corner_y(),
-                                right_target.target(j).right_corner_x(),
-                                right_target.target(j).right_corner_y());
+                              right_target.target(j).left_corner_y(),
+                              right_target.target(j).right_corner_x(),
+                              right_target.target(j).right_corner_y());
     h = right_target.target(j).left_corner_y() -
         right_target.target(j).right_corner_y();
-    double ang = h/ wid2;
+    double ang = h / wid2;
     double ang_err = ::std::abs(good_ang - ang);
     if (min_ang_err == -1.0 || min_ang_err > ang_err) {
       min_ang_err = ang_err;
@@ -105,69 +107,137 @@
                              right_target.target(right_index).right_corner_y());
 }
 
+class CameraHandler {
+ public:
+  void Received(const VisionData &target, ::aos::time::Time now) {
+    if (current_.received) {
+      last_ = current_;
+    }
+    current_.target = target;
+    current_.rx_time = now;
+    current_.capture_time =
+        now - ::aos::time::Time::InNS(target.send_timestamp() -
+                                      target.image_timestamp());
+    current_.received = true;
+  }
+
+  void CheckStale(::aos::time::Time now) {
+    if (now > current_.rx_time + ::aos::time::Time::InMS(50)) {
+      current_.received = false;
+      last_.received = false;
+    }
+  }
+
+  bool received_both() const { return current_.received && last_.received; }
+
+  bool is_valid() const {
+    return current_.target.target_size() > 0 && last_.target.target_size() > 0;
+  }
+
+  const VisionData &target() const { return current_.target; }
+  const VisionData &last_target() const { return last_.target; }
+
+  ::aos::time::Time capture_time() const { return current_.capture_time; }
+  ::aos::time::Time last_capture_time() const { return last_.capture_time; }
+
+ private:
+  struct TargetWithTimes {
+    VisionData target;
+    ::aos::time::Time rx_time{0, 0};
+    ::aos::time::Time capture_time{0, 0};
+    bool received = false;
+  };
+
+  TargetWithTimes current_;
+  TargetWithTimes last_;
+};
+
+::aos::vision::Vector<2> CalculateFiltered(
+    const CameraHandler &older, const CameraHandler &newer,
+    const ::aos::vision::Vector<2> &newer_center,
+    const ::aos::vision::Vector<2> &last_newer_center) {
+  const double age_ratio =
+      (older.capture_time() - newer.last_capture_time()).ToSeconds() /
+      (newer.capture_time() - newer.last_capture_time()).ToSeconds();
+  return ::aos::vision::Vector<2>(
+      newer_center.x() * age_ratio + (1 - age_ratio) * last_newer_center.x(),
+      newer_center.y() * age_ratio + (1 - age_ratio) * last_newer_center.y());
+}
 
 void Main() {
   StereoGeometry stereo(constants::GetValues().vision_name);
   LOG(INFO, "calibration: %s\n",
       stereo.calibration().ShortDebugString().c_str());
 
-  VisionData left_target;
-  aos::time::Time left_rx_time{0, 0};
-
-  VisionData right_target;
-  aos::time::Time right_rx_time{0, 0};
+  CameraHandler left;
+  CameraHandler right;
 
   ::aos::vision::RXUdpSocket recv(8080);
   char rawData[65507];
-  bool got_left = false;
-  bool got_right = false;
 
   while (true) {
     // TODO(austin): Don't malloc.
     VisionData target;
     int size = recv.Recv(rawData, 65507);
-    aos::time::Time now = aos::time::Time::Now();
+    ::aos::time::Time now = ::aos::time::Time::Now();
 
     if (target.ParseFromArray(rawData, size)) {
       if (target.camera_index() == 0) {
-        left_target = target;
-        left_rx_time = now;
-        got_left = true;
+        left.Received(target, now);
       } else {
-        right_target = target;
-        right_rx_time = now;
-        got_right = true;
+        right.Received(target, now);
       }
     } else {
       LOG(ERROR, "oh noes: parse error\n");
       continue;
     }
 
-    if (now > left_rx_time + aos::time::Time::InMS(50)) {
-      got_left = false;
-    }
-    if (now > right_rx_time + aos::time::Time::InMS(50)) {
-      got_right = false;
-    }
+    left.CheckStale(now);
+    right.CheckStale(now);
 
-    if (got_left && got_right) {
-      bool left_image_valid = left_target.target_size() > 0;
-      bool right_image_valid = right_target.target_size() > 0;
+    if (left.received_both() && right.received_both()) {
+      const bool left_image_valid = left.is_valid();
+      const bool right_image_valid = right.is_valid();
 
       auto new_vision_status = vision_status.MakeMessage();
       new_vision_status->left_image_valid = left_image_valid;
       new_vision_status->right_image_valid = right_image_valid;
       if (left_image_valid && right_image_valid) {
-        ::aos::vision::Vector<2> center0(0.0, 0.0);
-        ::aos::vision::Vector<2> center1(0.0, 0.0);
-        SelectTargets(left_target, right_target, &center0, &center1);
+        ::aos::vision::Vector<2> center_left(0.0, 0.0);
+        ::aos::vision::Vector<2> center_right(0.0, 0.0);
+        SelectTargets(left.target(), right.target(), &center_left,
+                      &center_right);
+
+        // TODO(Ben): Remember this from last time instead of recalculating it
+        // each time.
+        ::aos::vision::Vector<2> last_center_left(0.0, 0.0);
+        ::aos::vision::Vector<2> last_center_right(0.0, 0.0);
+        SelectTargets(left.last_target(), right.last_target(),
+                      &last_center_left, &last_center_right);
+
+        ::aos::vision::Vector<2> filtered_center_left(0.0, 0.0);
+        ::aos::vision::Vector<2> filtered_center_right(0.0, 0.0);
+        if (left.capture_time() < right.capture_time()) {
+          filtered_center_left = center_left;
+          new_vision_status->target_time = left.capture_time().ToNSec();
+          filtered_center_right =
+              CalculateFiltered(left, right, center_right, last_center_right);
+        } else {
+          filtered_center_right = center_right;
+          new_vision_status->target_time = right.capture_time().ToNSec();
+          filtered_center_right =
+              CalculateFiltered(right, left, center_left, last_center_left);
+        }
+
         double distance, horizontal_angle, vertical_angle;
-        stereo.Process(center0, center1, &distance, &horizontal_angle,
-                       &vertical_angle);
-        new_vision_status->left_image_timestamp = left_target.image_timestamp();
-        new_vision_status->right_image_timestamp = right_target.image_timestamp();
-        new_vision_status->left_send_timestamp = left_target.send_timestamp();
-        new_vision_status->right_send_timestamp = right_target.send_timestamp();
+        stereo.Process(filtered_center_left, filtered_center_right, &distance,
+                       &horizontal_angle, &vertical_angle);
+        new_vision_status->left_image_timestamp =
+            left.target().image_timestamp();
+        new_vision_status->right_image_timestamp =
+            right.target().image_timestamp();
+        new_vision_status->left_send_timestamp = left.target().send_timestamp();
+        new_vision_status->right_send_timestamp = right.target().send_timestamp();
         new_vision_status->horizontal_angle = horizontal_angle;
         new_vision_status->vertical_angle = vertical_angle;
         new_vision_status->distance = distance;
@@ -180,9 +250,10 @@
     }
 
     if (target.camera_index() == 0) {
-      LOG(DEBUG, "left_target: %s\n", left_target.ShortDebugString().c_str());
+      LOG(DEBUG, "left_target: %s\n", left.target().ShortDebugString().c_str());
     } else {
-      LOG(DEBUG, "right_target: %s\n", right_target.ShortDebugString().c_str());
+      LOG(DEBUG, "right_target: %s\n",
+          right.target().ShortDebugString().c_str());
     }
   }
 }