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Blog Post | Adding Traffic Signal Symbols to Animations
So, you're working on your t-bone impact animation for trial, and now you want to put a simple traffic signal timing symbol into your crash animation, rather than using text annotation. As is usually the case with Virtual CRASH 3, there is a way to do it by taking advantage of Virtual CRASH's amazing versatility. Below we will review the procedure for creating a traffic signal symbol with animated signal timing. Here we see the final animation:
Let's start with our aerial photo used in this example. It was simply imported from Google Earth:
Using the scaling procedure shown in the video below, and reviewed in Chapter 9 of the User's Guide (see the vCRASH Academy page), we scaled our Google Earth image after importing it.
Below you can see the imported and scaled aerial photo in Virtual CRASH 3:
Next we added the likely vehicle paths leading into the intersection. We used the auto-driver feature to let Virtual CRASH adjust the vehicle steering angles to best follow the paths. The videos below illustrate the auto-driver system:
In this case, the driver of Vehicle 1 (white car) ran the red light, thereby causing a collision with Vehicle 2 (blue pickup). The driver of Vehicle 2 began accelerating immediately after his light changed to green, and impact occurred shortly after as he entered Driver 1's lane. Vehicle 1 was given an initial velocity and Vehicle 2 was started a rest, but made to accelerate forward from rest using the sequences menu.
We wanted to show the animated impact sequence, as well as depictions of the signal timing. First, we drew a simple filled rectangle for the traffic signal symbols:
Then, we drew a filled circle and extruded it. We made the rectangle above and our circles large enough to be clearly visible in our final animation.
The extruded circle was cloned two times so that we obtained three extruded circles. The parent filled circle was then hidden from view. The extruded circles were then colored red, yellow, and green. The extruded height was set to 0.01 ft.
Since 2-D shapes cannot be elevated above the x-y plane, we extruded the circular shapes in order to make new shapes which could be elevated in z. Selecting the position-local menu in the left side control panel will reveal the x,y,z positions of the extruded circle objects. The z positions can be set as a function of time. The way we can give the illusion of the circular shapes disappearing (or appearing) is by simply dropping them instantly below (or raising them above) the aerial image. By left-clicking on the empty box icon next to the z coordinately, one gains access to the graph options which allow the user to set the z position as a function of time.
We used the "interval" graph type for this project. This option lets one set specific points in z versus time for the selected extruded object. We simply placed the object below the x-y plane when it was to be invisible, and instantly moved it to z = 0 when it was to appear in our animation. So, if the red extruded circle is to represent a red traffic signal, when the red signal is to turn on in your animation, simply change the z coordinate of your red extruded circle from below to above the x-y plane. You can also simply set the z coordinate to zero when they are to appear visible so long as your extrusions have height greater than zero.
You will need to adjust the z positions of all lights in your animation such that you reproduce the illusion of the signal timing. Here we see all three lights on the same z versus time diagram:
So at time = 0 seconds, we see a green signal above the x-y plane:
while simultaneously below the x-y plane, we see yellow and red:
At time = 0.5 seconds, the green signal drops below the x-y plane and the yellow signal elevates above the x-y plane.
This same procedure can be used to animate many different system, where one wants an object to instantly disappear. Again, here is the final animation.
Alternative approach using the semaphore object
One could also use the 3D semaphore shape in the library and turn it on its back to face upward, as shown below, to accomplish the same task. The semaphore object comes with signal timing properties built in, so there would be no need to adjust the z-position graphs. Watch the help > helpers > semaphore Virtual Tutor lesson for more detail.
Here we see similar techniques used by a European accident reconstructionist.
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