Setup and stereo reconstruction.
(A) The setup consists of a 40x40x40cm3 box illuminated from above with a halogen light. Hoverflies were filmed in the box with a fast camera through a two-way mirror at a rate of 1600 frames per second in full resolution (1280 by 800 pixels). The mirror was tilted at an angle of 45° to make the hoverfly see a uniform white wall (i.e. the reflection of the white light-diffusing ceiling). A manual switch was used to trigger the camera and simultaneously turn off the power of the electromagnet, thus releasing the resting fly and causing it to fall. A set of mirrors was used to split the images, giving two different views of the experimental box. (B) Example of a split image obtained with the set of mirror with the two trajectories superimposed. The two trajectories were used to obtained a 3-D reconstruction with the MATLAB stereo vision toolbox.