AERO User Guide =============== AERO is started with the command xaero You may start the program with command line parameters to compute a sequence off-line (in batch mode). Command line parameters are : -b run program in batch mode -f name specify input file of sequence or world (single state) this parameter works if not in batch mode -s name specify output file for sequence -nb count number of images to be computed for sequence Without command line parameters, the program starts in interactive mode and displays the editor window. Scenes may loaded from file or edited from scratch. All objects can be given material types. The regular table of materials may be replaced by loading another table from file, or it may be edited (only possible if at least a single object is in the scene). EDITOR WINDOW & OBJECT WINDOW ----------------------------- New objects may be selected from the menu "insert new object": sphere, cylinder, cuboid (box), immovable point or plane. They appear in the center of the coordinate system and may be translated using cursor keys in one of the 2D views or the appropriate buttons in the object window. Objects may be rotated using the buttons in the object window. For each object, material and color may be set independently. The material determines an objects density, which together with its volume determines its weight. However, one may choose button "no gravitation" to inhibit the gravitational force on an object. Button "fixed" locks an object in its position (it cannot be moved by gravitation or other forces, e.g. collision with moving objects). Objects may be selected one after the other by pressing the "select next object" button in the main window. A selected object may be deleted by pressing the appropriate button or liked to another object by selecting one of the link types: rod, spring, damper or joint. The object to be linked with and some parameter have to be specified. The link position is displayed with an "X". Links may be removed by first selecting the link and then deleting the selected link by pressing the appropriate buttons. Forces may be exerted onto objects (button "add force"): directed force (always directed to the current position of another object), force with respect to an object, and force with respect to the coordinate system. The target point and the goal position (directed force) or the direction (other forces) have to be specified together with the duration and strength of the force. Quite a number of parameters for performing the rigid body simulation may be entered from the parameters menu (e.g. setting the gravity value, frames per second ratio, or the computation and simulation methods). The buttons "zoom in" and "zoom out" change the camera zoom. Button step computes a single successor image according to the rules selected. Note, this function cannot be un-done. ANIMATION WINDOW ---------------- Button "Animation" opens the animation window with all objects in their current state. Note, not all image frames computed will also be stored! Only those image frames marked as "sync points" will be stored (use button "sync point" / "no sync point" for setting/unsetting). Similar to movie editing, cuts may be inserted into an animation sequence by means of the button "same scene" / "new scene". The animation may be controlled via the buttons representing the functions of a video recorder. For returning to the editor window, press button "close". CALCULATION PARAMETERS ---------------------- integration step width error control accuracy between steps min. step width max. step width The simulator integrates the acceleration and velocity to compute the positions of the objects. It uses a Runga-Kutta process to do this. If the error control is not set, it is done with the constant time-step-rate of "integration step width". If the user choose "error control", the value in "accuracy between steps" is used to compute a step rate, which lies between min. and max. step width. collision detection collision step width max. resting speed min. penetration depth min. sliding speed min. rolling speed spring impact If the collision detection is active, at least every "collision step width" a collision detection is invoked to determine if objects penetrate each other. The collision detection routine generates a list of collision points with the velocity and penetration depth. The collision velocities that are lower than the "max. rest speed" are handled as touching, all others as impact. The penetration depth should always be greater than the "min. penetration depth". The "min. sliding speed" and "min. rolling speed" determine the type of friction which is applied: static or dynamic friction. Normally, an analytic solution to determine the velocities after an impact is used. The computation method by using springs and dampers (penality-method) for the collision handling is used for the handling of the touching process and can also be applied to impacts when "spring impact" is activated. Please note that the material constants of the material-table are used in the analytical and penality method. random gravitation random gravitation rate By setting "random gravitation" a random value is added to the gravity applied at every object. joint damping joint spring constant rod damping rod spring constant min. spring stretching The upper values are necessary because of the approximation of a "rod" and a "joint" by a spring and damper pair. air resistance cw for sphere cw for cuboid cw for cylinder A simplified air resistance can be activated, which uses the projected body-plane and the cw-value to compute a force opposing the direction of movement.