Prelude | A Quick Start for the Impatient User


Introduction

Thanks for purchasing Virtual CRASH! You will find Virtual CRASH to be an extremely powerful and versatile simulation tool which can be quickly learned [1]. This Prelude is for those users eager to jump right into the simulation environment and to start moving cars around. Here, you will quickly learn how to select a car from the vehicle list and import it into the scene. You’ll next learn how to give the car an initial velocity. First, we will review the amazing “Virtual Tutor.”

Version 3 and Version 4

While most of the contents of this User’s Guide was originally written for Virtual CRASH 3, the contents are directly applicable to Virtual CRASH 4 as well; this is because version 4 was built on the version 3 platform, so version 4 users will enjoy all the amazing functionality and features from version 3, with additional added features such as point cloud importing, the Easy Surface Builder, Total Station Surface Builder, Google Earth integration, and more. Chapter 20 covers various version 4 features.

 The Virtual Tutor

The first thing you should familiarize yourself with in Virtual CRASH 3 is the innovative “Virtual Tutor” feature [2]. The Virtual Tutor will help you understand where to access most of the functions within Virtual CRASH by literally taking over your mouse and showing you! To access the Virtual Tutor help topics, go to the lower portion of the left-side control panel and left-click on “help”.

Now you should see a list of topics from which you can select. Note, the “player speed” option is above the list, and can be used to slow down or speed up the lessons.

Next, select your lesson by left-clicking a topic and watch.

Select a Vehicle and Place it into the Scene 

Let’s put a car into our simulation. At startup, you should see something like what is shown below. Note, in Virtual CRASH 4, vehicle browsing has been improved with the updated Gallery browser (see: http://www.vcrashusa.com/guide-chapter20/#Gallery). 

Move your mouse to the left side control panel, and left-click the “+” sign next to “car” to reveal the vehicle makes list.

Next, using either your mouse’s scroll wheel, or the scroll bar (blue arrow), scroll down the list until you find the desired vehicle make, then press the “+” sign to reveal the available models. Hover your mouse over the desired model, left-click and hold, then drag your mouse cursor into the environment and release the left mouse button.

You should now see your vehicle in the environment. Keep in mind, depending on the vehicle, you may occasionally see mismatched wheel positions with respect to wheel wells defined in the vehicle mesh. This is because, while there are over 400 unique vehicle meshes in the Virtual CRASH library [3], there are even more vehicles defined, and therefore meshes (such as the generic hatchback) are often reused as exemplars for other vehicles. Correcting wheel well positions and importing custom vehicle meshes are both discussed further in this guide.

Specify Initial Conditions

Now that you have your vehicle imported into the scene, you are now ready to give it some initial speed. First, left-click on the upper tool bar to pull down the drop down menu shown below, and then left-click on “Select, Move And Manipulate.” Left-click on your vehicle and you should see fast control icons appear. These are discussed further in the guide.

Each vehicle in Virtual CRASH 3 has its own local reference frame [4]. The local \(x-\)axis ( \( \hat{x}^{\prime}\) ) can be imagined to extend along the center dividing-line of the vehicle, pointing from rear to front, through the center-of-gravity. The local \(y-\)axis (\(\hat{y}^{\prime}\)) can be imaged to run orthogonal to the \(x-\)axis, directed from passenger side through the driver side, running through the center-of-gravity. The local \(z-\)axis (\(\hat{z}^{\prime}\)) is given by the cross product \( \hat{z}^{\prime} = \hat{x}^{\prime} \times \hat{y}^{\prime} \). With this in mind, right-click on your vehicle, and you should see a fast control menu appear (see below). Here you can specify the initial velocity vector magnitude (v), velocity vector angle with respect to the vehicle’s local \(x-\)axis (vni), velocity vector angle with the local \(x-y\) plane (vnz), the vehicle’s yaw velocity about its local \(z-\)axis (omega-z), and yaw orientation angle with respect to the Earth frame (yaw). These are also controlled using the left-side control panel as will be discovered in later chapters. For now, experiment by left-clicking on the slider controls, hold, and drag your mouse side to side for each of these parameters. You should see your car move and quickly adjust trajectories in real time as you vary your inputs!


Notes:

[1] When using any physics simulation software tool, it is imperative the user perform all necessary consistency checks to ensure the simulated results are in good agreement with expectations from standard forensic techniques. It is also imperative the user understand the limitations of the simulation tool, as well as understand potential sources of uncertainties in simulated results, including but not limited to, user uncertainties in input parameters as well as those related to object positions and orientations within the simulation environment.

[2] You can find an infographic on using the “Virtual Tutor” on the vCRASH Academy site at: http://www.vcrashusa.com/s/VirtualTutor.jpg

[3] The full vehicle and objects list is available online at: http://www.vcrashusa.com/s/VirtualCRASH_3_and_4_Vehicles_Objects_List.pdf. It is recommended to always consult this list first before starting a project to find the best matches for your subject vehicles. Note, it is also recommended that you ensure all vehicle properties, including size, inertial properties, wheel placement, drive axle, etc,  are properly set using appropriate values for your subject vehicles. Vehicle properties can be obtained through third-parties such as the Canadian Vehicle Specifications database (http://www.carsp.ca/research/resources/safety-sources/canadian-vehicle-specifications/), Expert Autostats (http://www.4n6xprt.com/), or Lightpoint Scentific (http://lightpointdata.com/).

[4] See Appendix 3 | The Virtual CRASH Coordinate System.



Tags: Quick start, vni, vnz, omega-z, how to watch tutorial, virtual tutor, make a vehicle, put vehicle in scene, how to create simulation. 


 

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