The r_wobj, θ_wobj, φ_wobj coordinates computed from the mechanical signals at the whisker base can be used to reconstruct the shape of the peg.

(Top left) This panel shows a still image of the rat’s head, the peg location, and the tracked whisker (red). This still image can be compared with the videos in the other panels, all of which show different views of the peg “reconstruction” over time. (Top center) The time-varying 3D whisker-object contact point (rwobj, θwobj, φwobj) computed from the mechanical signals is plotted in whisker-centered coordinates. The whisker is the black, tapered, dotted line. Each magenta dot represents a 3D contact point on the peg with respect to the whisker. Each dot is computed based on mechanical data obtained from a single video frame (1 ms resolution). These are the identical points plotted in all other video panels, but are now plotted in their correct 3D spatial locations relative to the whisker. (Top right) Top-down view and front-on view of the rat as it whisks against the peg. The rat first whisks forward against the back of the peg, and then whisks backwards against the front of the peg. The whisker is traced in red for those frames in which it is in contact with the peg. (Bottom row) All videos in the bottom row show the gradual reconstruction of the peg’s contour based on computing contact points from the mechanical signals at the whisker base. Because the rat whisks both forward and backwards against the peg, reconstructions are observed for the peg’s front and back sides. Contact points directly tracked from the video (“ground truth”) are shown as black dots. Contact points computed from mechanical signals are shown as transparent magenta dots. (Bottom left and center) The left panel shows an isometric view of the rat’s head along with the time-varying whisker-peg contact points, while the center panel shows an expanded view of the contact points. Note that the contact points form two distinct vertical lines, indicating contact with the front and the back of the peg. (Bottom right) Reconstruction of the peg contour in top-down and front-on views, matching the videos directly above. The top-down view reveals that the largest errors are found in the estimate of radial distance, rather than in estimates of the angles of contact. (MP4)