72 lines
4.6 KiB
TeX
72 lines
4.6 KiB
TeX
\subsection{Grasp Task}
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\label{grasp}
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\subsubsection{Completion Time}
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\label{grasp_tct}
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On the time to complete a trial, there was one statistically significant effect %
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of \factor{Target} (\anova{7}{2868}{37.2}, \pinf{0.001}) %
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but not of \factor{Hand} (\anova{5}{2868}{1.8}, \p{0.1}, see \figref{results/Grasp-CompletionTime-Hand-Overall-Means}).
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Targets on the back and the left (\level{B}, \level{LB}, and \level{L}) were slower than targets on the front (\level{LF}, \level{F}, and \level{RF}, \p{0.003}) {except for} \level{RB} (back-right) which was also fast.
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\subsubsection{Contacts}
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\label{grasp_contacts_count}
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On the number of contacts, there were two statistically significant effects: %
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\factor{Hand} (\anova{5}{2868}{5.2}, \pinf{0.001}, see \figref{results/Grasp-ContactsCount-Hand-Overall-Means}) %
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and \factor{Target} (\anova{7}{2868}{21.2}, \pinf{0.001}).
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Less contacts were made with \level{Tips} than with \level{None} (\qty{-13}{\%}, \p{0.02}) and \level{Occlusion} (\qty{-15}{\%}, \p{0.004});
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and less with \level{Mesh} than with \level{None} (\qty{-15}{\%}, \p{0.006}) and \level{Occlusion} (\qty{-17}{\%}, \p{0.001}).
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This result suggests that having no visible visual hand increased the number of failed grasps or cube drops.
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But, surprisingly, only \level{Tips} and \level{Mesh} were statistically significantly better, not \level{Contour} nor \level{Skeleton}.
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Targets on the back and left were more difficult (\level{B}, \level{LB}, and \level{L}) than targets on the front (\level{LF}, \level{F}, and \level{RF}, \pinf{0.001}).
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\subsubsection{Time per Contact}
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\label{grasp_time_per_contact}
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On the mean time spent on each contact, there were two statistically significant effects: %
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\factor{Hand} (\anova{5}{2868}{9.6}, \pinf{0.001}, see \figref{results/Grasp-MeanContactTime-Hand-Overall-Means}) %
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and \factor{Target} (\anova{7}{2868}{5.6}, \pinf{0.001}).
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It was shorter with \level{None} than with \level{Tips} (\qty{-15}{\%}, \pinf{0.001}), \level{Skeleton} (\qty{-11}{\%}, \p{0.001}) and \level{Mesh} (\qty{-11}{\%}, \p{0.001});
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shorter with \level{Occlusion} than with \level{Tips} (\qty{-10}{\%}, \pinf{0.001}), \level{Skeleton} (\qty{-8}{\%}, \p{0.05}), and \level{Mesh} (\qty{-8}{\%}, \p{0.04});
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shorter with \level{Contour} than with \level{Tips} (\qty{-8}{\%}, \pinf{0.001}).
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As for the \factor{Push} task, the lack of visual hand increased the number of failed grasps or cube drops.
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The \level{Tips} rendering seemed to provide one of the best feedback for the grasping, maybe thanks to the fact that it provides information about both position and rotation of the tracked fingertips.
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This time was the shortest on the front \level{F} than on the other target volumes (\pinf{0.001}).
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\subsubsection{Grip Aperture}
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\label{grasp_grip_aperture}
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On the average distance between the thumb's fingertip and the other fingertips during grasping, there were two
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statistically significant effects: %
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\factor{Hand} (\anova{5}{2868}{35.8}, \pinf{0.001}, see \figref{results/Grasp-GripAperture-Hand-Overall-Means}) %
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and \factor{Target} (\anova{7}{2868}{3.7}, \pinf{0.001}).
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It was shorter with \level{None} than with \level{Occlusion} (\pinf{0.001}), \level{Tips} (\pinf{0.001}), \level{Contour} (\pinf{0.001}), \level{Skeleton} (\pinf{0.001}) and \level{Mesh} (\pinf{0.001});
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shorter with \level{Tips} than with \level{Occlusion} (\p{0.008}), \level{Contour} (\p{0.006}) and \level{Mesh} (\pinf{0.001});
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and shorter with \level{Skeleton} than with \level{Mesh} (\pinf{0.001}).
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This result is an evidence of the lack of confidence of participants with no visual hand rendering: they grasped the cube more to secure it.
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The \level{Mesh} rendering seemed to have provided the most confidence to participants, maybe because it was the closest to the real hand.
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The \response{Grip Aperture} was longer on the right-front (\level{RF}) target volume, indicating a higher confidence, than on back and side targets (\level{R}, \level{RB}, \level{B}, \level{L}, \p{0.03}).
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\begin{subfigs}{grasp_results}{Results of the grasp task performance metrics for each visual hand rendering. }[
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Geometric means with bootstrap 95~\% \CI
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and Tukey's \HSD pairwise comparisons: *** is \pinf{0.001}, ** is \pinf{0.01}, and * is \pinf{0.05}.
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][
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\item Time to complete a trial.
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\item Number of contacts with the cube.
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\item Time spent on each contact.
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\item Distance between thumb and the other fingertips when grasping.
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]
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\subfig[0.4]{results/Grasp-CompletionTime-Hand-Overall-Means}
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\subfig[0.4]{results/Grasp-ContactsCount-Hand-Overall-Means}
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\par
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\subfig[0.4]{results/Grasp-MeanContactTime-Hand-Overall-Means}
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\subfig[0.4]{results/Grasp-GripAperture-Hand-Overall-Means}
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\end{subfigs}
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