STICK-3D

• Program Objectives

  The short program STICK-3D.EXE (right-click and "Save Target As") animates a stereoscopic 3-D wireframe hexapod that looks like a stick insect, with three degrees of freedom per leg. Its purpose is to help identify the features of a hexapod simulation that are necessary or not for the display, to start organize the structure of variables and modules, and to find a common platform for the simulation. The program is written in Turbo C 2.0 in 3 modules, one of graphics functions, one of nervous system, and one main that is essentially a large "dt" loop waiting for user commands.

• System Requirements

  The program was written for IBM PC or compatible computers, with an EGA graphics card with 128 kBytes video memory (allowing page-swapping flickerless display), and running Microsoft DOS 2.1 or later DOS (not Windows) operating system.

  Under Windows, 16 years later, the program still runs, but Windows 3.1 and above does not allow any direct access to the graphics memory; the Windows-controlled screen refresh conflicts with the program-controlled refresh, and as a result, the screen may flicker unbearingly on some machines. I lost the code diskettes during moving, so this cannot be changed....

  For the stereo 3D effect, you will need red/green or red/blue glasses salvaged from some Vincent Price movie show.

• Q U I C K S T A R T

  The first view of the hexapod is from a 3/4 rear right view. Press the [Arrow Keys] to modify the orientation of the insect until you find that you have a clear view of all the legs. If you get confused, press [R] to reset the original conditions.

  Now press [H] to enter the Hexapod control mode. Note that all the speeds are initially at zero and that all the legs are on the ground. Press [R] to randomize the leg positions at will (and at any time you think it is necessary). Start moving by pressing [+] several times, it increases the forward speed, and observe the pattern of the legs as they walk. They will end up in a form of alternating tripod. Once this is the case, try throw in some crab component (not too much!) with the left-right arrow keys, or vary the elevation of the hexapod to step over some invisible boulders with the up-down arrow keys.

  Finally, go back to the [D]isplay control mode, as the hexapod is walking, to try other commands. They are all listed in a help screen that you can call up by pressing F1.

• Keyboard Controls

  There are two modes of control of the simulation: the first is the control the [D]isplay and the second is to control the [H]exapod itself. The bottom line of the display, the "information line", shows which of the two modes is active [the default is DISPLAY]. Pressing [I] toggles that information line on or off. The key [F1] provides a help screen for the current [D]isplay or [H]exapod mode. To exit the program altogether, press [Esc].

  • [D]isplay controls

    • Orientation controls

      The [Arrow keys] control the orientation of the viewer around the hexapod, and the line of sight is always oriented towards the center of the hexapod. The angles are given from the point of view of the hexapod, as that seems to be more intuitive.

      The bearing is the angle at which the observer is in the horizontal plane, with 0 deg being straight ahead of the hexapod. [Left Arrow] increases it, that is the observer turns clockwise around the hexapod, and [Right Arrow] decreases it [default is 120 deg, right rear view].

      The elevation is the angle line of sight in the vertical plane, with 0 deg being horizontal. [Up Arrow] increases it, up to 90 deg, i.e. straight above, and [Down Arrow] decreases it [default is +20 deg, a slightly elevated point of view].

    • Proximity controls

      Getting closer or farther away from the hexapod can be done by pressing the [Home] ("home in") or [End] keys. The image size is automatically kept constant (like exactly compensating with a zoom lens as you move closer or farther), so all you will notice is a change in the proportions of the limbs. When really far away, the representation is quasi-isometric.

      The magnification, the overall size of the insect on the screen, is controllable through the [Pg Up] (increase, i.e. decrease the projection distance) and [Pg Dn] keys.

      If you lose track of your spatial orientation, press [R] to reset the default values for orientation and proximity controls.

    • Stereoscopic controls

      The program has the option of anaglyphic stereoscopic viewing, for which you must wear one of those red/green or red/blue glasses. PLEASE DO NOT TOUCH THE PLASTIC LENSES, AS THEY ARE DIFFICULT TO CLEAN. The red lens is always for the left eye, but you have a choice of green or blue for the right eye, as this depends more on the match between the glasses and the particular color settings of your monitor. Try the combination that gives the least amount of "ghosts", especially for the shadows, try also to use a red and green screen with red and blue glasses and vice-versa. To make the stereo viewing comfortable, dim ambient light and make sure there are no parasitic reflections on the screen. There are four anaglyphic options for stereoscopic viewing:

              [1] red and green, black background
              [2] red and green, light background
              [3] red and blue,  black background
              [4] red and blue,  light background
              [0] no stereoscopic view  (default)
      

      The [+] and [-] keys increase or decrease stereoscopic disparity. If you are not used to stereoscopic viewing, you may need to decrease the disparity. The program computes the real perspective but only an equivalent "convergence angle" is displayed in the information line. When 1280 ø 1024 resolution screens are available, the more natural side-by-side parallel stereoscopic viewing may be a viable option.

    • Environment control

      A series of ground dots can be toggled on or off by pressing [G], to help visualize the substrate. These dots are pseudo-randomly scattered like confetti on a flat ground. To simulate rugged terrain in the future, the dots could also have variable elevation and be linked to one another on a nearest neighbor basis to create a 3-D triangulated surface.

      The cast shadow of the hexapod can be toggled on or off by pressing [S]. The shadow is cast from a vertical light source and helps in fact to visualize the direction of gravity.

      Note that the refreshing rate of the display is faster when Ground, Shadow, Information line and stereo are toggled off.

  • [H]exapod controls

    The coordination control of the hexapod is quite simple. It is based on the two rules that (1) when a leg comes to the end of its extension and has to flex (the extension speed is equal to the hexapod speed, without skidding), the adjacent legs extend, no matter where they are in their own cycle, and (2) when a leg comes to the end of its flexion it extends. It is a local discrete control. Attempts have been made to model neurons based on Pearson and Zill publications, but the hexapod would always end up "locking up", for various reasons not discussed here. The current coordination control was written to make legs walk in a non-regular way (sometimes in a weird fashion!) to test its perception on the display, not to emulate any nervous system.

    The local control of the legs would be under proprioceptive and tactical sensory influence, but the user provides the higher brain controls of the hexapod. There are essentially four controls to cover the voluntary acts involved in walking, and they would be ideally combined simultaneously with two two-axis joysticks, as there are not enough practical keys on the keyboard to control both the display and the hexapod simultaneously. In the future, the hexapod, given a specific task, should decide on its own what combination of these four controls suit the immediate environment, based on remote sensing.

            [+] or [-] increase or decrease forward speed
            [F9] or [F10] turn [disabled] left or right
            [Arrow Up] or [Arrow Dn] increase or decrease ground clearance
            [Arrow Right] or [Arrow Left] crab to the right or left
    

• Bug reports

  (1) If you crab faster than you walk, you'll break a leg and the program will crash. Sorry, but I don't have the source code any more to fix this, so tread carefully.

  (2) If the hexapod gets clearly in a confused state, and this can happen due to the simplisctic leg control, you can press [R] to randomize leg position with all six legs on the ground.

                   [F1] Help for DISPLAY control

[Arrow Up]    increase elevation; see from more above
[Arrow Down]  decrease elevation; see from more horizontal
[Arrow Left]  increase bearing; turn clockwise around hexapod
[Arrow Right] decrease bearing; turn counterclockwise around hexapod

[Home]  home in on hexapod but keep image size constant
[End]   get away from hexapod but keep image size constant
[Pg Up] increase magnification» decrease screen distance
[Pg Dn] decrease magnification» increase screen distance

[1] stereo left RED right GREEN, black background [2] light background
[3] stereo left RED right BLUE,  black background [4] light background
[+] or [-] increase or decrease stereoscopic effect
[0] no stereo

[S] toggle cast shadow
[G] toggle ground dots

[I] toggle information line
[R] resets default viewing values
[H] toggle to Hexapod control
[Esc] quit program


                   [F1] Help for HEXAPOD control

LEFT JOYSTICK:
[+] increase forward speed
[-] decrease forward speed
[F9]  turn left  [disabled]
[F10] turn right [disabled]

RIGHT JOYSTICK:
[Arrow Up]    increase ground clearance
[Arrow Down]  decrease ground clearance
[Arrow Left]  crab to the left (not too much)
[Arrow Right] crab to the right (not too much)

[I] toggle information line
[R] randomize leg position
[D] toggle to Display control
[Esc] quit program