Bus (streets vehicle): Importing and configuring

  • The import and configuration of road vehicles differs only in a few aspects from that of rail vehicles. Especially the differences will be discussed in this article.

    1 Construction in Blender

    For the placement of the vehicle in Blender one must first assume that the bus is lifted in such a way that the suspension of the wheels is just about completely relieved (unloaded). In this position and assuming that the floor corresponds to the Z=0 coordinate, the bus is constructed. The meshes of the wheels touch the Z=0 coordinate "normally".

    Since the exact spring strength and weight are only configured in the ContentTool, it is recommended to first import only the car body and the wheels into the ContentTool and especially not to place any animations, lights, etc. yet. Then (only) the chassis animations are configured, the suspension parameters and the vehicle mass are set and then the vehicle behavior is viewed in LOTUS. Only when the appropriate corrections have been made (where the height of the "sprung" bus model could be adjusted) and the suspension behavior is exactly as you want it, the further import will be continued.

    The pivot points of the wheels should, of course, be on the axle of the wheels and, in the case of steered axles, in the pivot point of the steering knuckle.

    2 Animations

    The body of a solo bus or the front part of an articulated bus is assigned to the root animation "Main". The empty weight and center of gravity in the empty state of the car or, in case of articulated buses, the front part of the car must be entered in the Main animation properties.

    In the further hierarchy, first the suspension, then the steering and finally the rotation of the wheels are configured for each wheel:

    • The suspension is a displacement animation with the direction x=0.0, y=0.0 and z=1.0 and the variable "spring_Wheel_m_{axle index}_{side}". The remaining values remain at their default values.
    • The respective steering is a rotation with the axis of rotation x=0.0, y=0.0 and z=1.0 and the variable "steering_Wheel_m_{axis index}_{side}". The remaining values remain at their default values.
    • The actual rotation of the wheels is a rotation with the axis of rotation x=-1.0, y=0.0 and z=0.0 and the variable "alpha_Wheel_deg_{axis index}_{side}". The remaining values remain at their default values.

    3 Car body physics

    For the vehicle to be able to drive, it naturally needs wheels. :-)

    The axles of the vehicle are configured in the section "Road vehicle". For each axle you have to create an entry from front to back and configure it as follows:

    • Name: Just for the list for recognition
    • Y position: At which position in longitudinal direction is the axis located?
    • Diameter: The wheel diameter
    • Width: Measured from wheel outer edge to wheel outer edge
    • Tire width: is measured per tire
    • Spring hardness: the harder the suspension is, the higher the vibration frequency (here, poor performance can still cause problems at the moment) but the smaller the spring travel
    • Damping: the higher the damping, the faster the suspension "calms down", but too much damping has a negative effect on the general spring behaviour (the spring is deprived of its ability to return).
    • Rotational inertia: this value has an influence on how the wheel behaves when spinning: The higher this value is, the lower the acceleration of the wheel rotation during spin.
    • Index trailer: Assigns to the axle the vehicle part to which it is attached
    • Actively steered: Steering turn of the wheels also at standstill (because being moved via the steering wheel), if, on the other hand, the check mark is not set, then the steering turn occurs passively, i.e. only through the movement of the vehicle on an arc, as for example with the third axle of the DL.

    4 Articulated bus

    The trailer is a separate animation type that must be subordinated to the main car - so it's kind of like an articulated railcar. The parameters of the trailer animation should be almost self-explanatory.

    In the axle configuration there is a special parameter to specify the index of the car body to which the axle should be attached.