Updated low level angle-to-ball feature.

doc/manual.tex

@@ -13,6 +13,7 @@
 \usepackage{hyperref,graphicx}
 \usepackage{fullpage}
 \usepackage{enumitem}
+\usepackage{subcaption}
 
 \title{RoboCup 2D Half Field Offense \\ Technical Manual}
 \author{Matthew Hausknecht}
@@ -273,9 +274,10 @@ the magnitude of self velocity will be set to zero.
 
 \subsubsection{Angular Features}
 
-\textit{Angular features} (e.g. the angle to the ball), are encoded as two
-floating point numbers -- the $sin(\theta)$ and $cos(\theta)$ where
-$\theta$ is the original angle.
+\textit{Angular features} (e.g. the angle to the ball), are encoded as
+two floating point numbers -- the $sin(\theta)$ and $cos(\theta)$
+where $\theta$ is the original angle in radians. Figure
+\ref{fig:ang_example} provides examples of the angular encoding.
 
 This encoding allows the angle to vary smoothly for all possible
 angular values. Other encodings such as radians or degrees have a
@@ -283,6 +285,34 @@ discontinuity that when normalized, could cause the feature value to
 flip between the maximum and minimum value in response to small
 changes in $\theta$.
 
+Given an angular feature $\langle \alpha_1, \alpha_2 \rangle$ we can
+recover the original angle $\theta$ (in radians) by taking the
+$cos^{-1}(\alpha_2)$ and multiplying by the sign of $\alpha_1$.
+
+\begin{figure*}[htp]
+  \centering
+  \subcaptionbox{Angular Encoding}{
+    \includegraphics[width=.4\textwidth]{figures/AngExample}
+  }
+  \hspace{3em}
+  \subcaptionbox{Additional Examples}{
+    \includegraphics[width=.3\textwidth]{figures/AngFeatExample}
+  }
+  \caption{\textbf{Angular Encoding:} Objects on the agents left/right
+    side result in a negative/positive $sin(\theta)$. $cos(\theta)$ is
+    positive in front of the player and negative behind. For example,
+    an object directly in front of the player would have angular
+    features of $sin(\theta)=0, cos(\theta)=1$. Additional examples:
+    \textbf{Angle to ball} $\theta=60^\circ$ or $1.0472$ radians. This
+    results in angular features $\langle sin(\theta)=.86,
+    cos(\theta)=.49 \rangle$. \textbf{Angle to teammate}:
+    $\theta=135^\circ, 2.35$ radians. $\langle sin(\theta)=.71,
+    cos(\theta)=-.71 \rangle$. \textbf{Angle to Opponent}:
+    $\theta=-90^\circ$ or $-1.57$ radians. $\langle sin(\theta)=-1,
+    cos(\theta)=0 \rangle$.}
+  \label{fig:ang_example}
+\end{figure*}
+
 \subsubsection{Distance Features}
 
 \textit{Distance features} encode the distance to objects of

src/feature_extractor.cpp

@@ -62,7 +62,7 @@ void FeatureExtractor::addLandmarkFeatures(const rcsc::Vector2D& landmark,
     addFeature(0);
   } else {
     Vector2D vec_to_landmark = landmark - self_pos;
-    addAngFeature(self_ang - vec_to_landmark.th());
+    addAngFeature(vec_to_landmark.th() - self_ang);
     addDistFeature(vec_to_landmark.r(), maxHFORadius);
   }
 }

src/lowlevel_feature_extractor.cpp

@@ -127,8 +127,9 @@ const std::vector<float>& LowLevelFeatureExtractor::ExtractFeatures(
   // Angle and distance to the ball
   addFeature(ball.rposValid() ? FEAT_MAX : FEAT_MIN);
   if (ball.rposValid()) {
-    addAngFeature(ball.angleFromSelf());
-    addDistFeature(ball.distFromSelf(), maxHFORadius);
+    addLandmarkFeatures(ball.pos(), self_pos, self_ang);
+    // addAngFeature(ball.angleFromSelf());
+    // addDistFeature(ball.distFromSelf(), maxHFORadius);
   } else {
     addFeature(0);
     addFeature(0);