Finger identification apparatus

diff --git a/tex/3-input.tex b/tex/3-input.tex
index 3bf68ece29290e0e90beda2796e4d92a5eedbef7..d9901d817a2d60fe16b6437f24e677ca4335ac51 100644 (file)
--- a/tex/3-input.tex
+++ b/tex/3-input.tex
@@ -572,7 +572,17 @@ We will discuss how we leverage this new input space in a systematic way.
 
 \subsubsection{Prototyping apparatus}
 
-Before searching for a technology suitable for a product we have to investigate the benefits of this information and how to use it
+This project is a typical HCI project in which we investigate the benefits and limitation of an interaction paradigm befoer the technology is ready to implement it in consumer electronics products.
+The advantage is that research for such a technology will happen only if and when the benefits will balance the cost.
+Even if such technology is not ready yet, the HCI community regularly uses alternative technologies that necessarrily make compromises.
+In some cases we just imagine the technology is there and works perfectly.
+The wizard of Oz technique consists in having an operator executing the actions on the users behalf, with any other technology.
+This is not always necessary.
+In the case of finger identifications, the Glass+Skin study just indicated participants the finger they wanted them to use.
+Other methods make assumptions on the inputs \cite{ghomi13,wagner14}, but it limits the resulting interaction techniques.
+Finally we can use alternative technologies.
+Either they only work for specific devices, like projection-based tabletops, or they use invasive methods with markers.
+We prefer the last method since it allowed us to build prototypes for tabletops, tablets and smartphones, without limitations on the input vocabulary.
 
 \begin{figure}[htb]
   \centering
@@ -585,6 +595,16 @@ Before searching for a technology suitable for a product we have to investigate
   \caption[Finger identification prototypes.]{Three implementations of finger identification prototypes. The first one uses gametracks to locate fingers on a tabletop. The two other ones use color markers with a camera to track fingers on a tablet and a smartphone.}
 \end{figure}
 
+The \reffig{fig:hotfingers-prototypes} shows the three prototypes.
+The tabletop prototype combines two sources of information.
+The first one is the 2D coordinates of the contact points.
+The second one is the 3D position of every finger that we sense with GameTraks\footnote{\href{https://en.wikipedia.org/wiki/Gametrak}{https://en.wikipedia.org/wiki/Gametrak}}.
+GameTracks sense a 3D position by measuring the length and angles of a string attached to a joystick.
+This method requires a calibration and strings attached to every finger, but it is not sensible to occlusion forr example.
+The tablet and smartphone prototypes used color markers on every finger, as well as an external camera.
+It requires calibration as well and it is sensible to occlusion.
+However having no strings attached to the fingers is more convenient for interacting on smaller devices.
+
 \subsubsection{Input vocabulary}