Blog Post | Make Your Own Vehicle Modifications
Suppose you have a case involving a Ford Explorer SUV police vehicle, which had lights and push bumper, and you need to add it to your Virtual CRASH simulation, but this vehicle is not in the Virtual CRASH database. Don't give up. You can make this yourself using the 3D modeling capabilities of Virtual CRASH!
First, let's start with our base vehicle. A Ford Explorer SUV:
Let's place it at (x,y) = (0,0), and yaw = 0 degrees.
Next, let's bring in a Crown Victoria police cruiser from the database, which we'll use for parts:
We're going to remove the push bumper and lights from the Crown Vic, and add them to the SUV. Go to the "elements" selection type:
Using the rectangular box selection tool, carefully select only the polygons from the push bumpers.
Go to the faces menu in the left-side control panel, and press "detach." You should now see a new entry in the objects list. Before moving the push bumper, change the object selection type back from "Elements" to "Object" so that you do not accidentally select and move individual polygons from the push bumper. Now you can move the push bumper away from the Crown Vic.
Next, repeat this same process for the siren lights:
In this case, because the siren lights penetrated inside of the roof's polygons, you'll like also have to select the roof as well. Do not be concerned with this, simply detach and separate from the Crown Vic.
Next, delete the Crown Vic.
Go back to the "Elements" selection type, and left-click on the roof polygons, and press delete. You should now see only the siren lights and push bumper. Switch back to "Object" selection type once you have done this.
Re-position the siren lights and push bumper onto the SUV.
Next, use a box to fully enclose the SUV, making sure the front and top sides of the box are in contact with the outermost polygons. Take note of the box's overall length and height. Once we have our final vehicle model imported, we will change the overall length and height to match our measurements from this step.
Next, delete the axles from the SUV. Here we also colorized the push bumper polygons to black.
Next, select the siren, push bumper, and SUV objects, then select Physics > Remove Physics From Selection.
Keeping these three objects simultaneously selected, go to Project > Export, and save your new model as a .vcm file.
Create a new instance of the Ford Explorer SUV from the vehicle database as you did at the start of the project. Next, open your Windows File Explorer, and find the icon for the .vcm file you saved. Left-click and hold, then drag the icon of the .vcm file directly on top of the new Explorer object, and release. You will be prompted "Do you want to replace current mesh?"
You will notice the over all length and height of the SUV are still based on the default model from the database, and so are both too small. The overhang distance will also need to be adjusted. This is why the wheel wells appear to be shifted forward:
The original overall length was 15.331 ft and the new length is 15.779 ft. This means the front-most surface of the new SUV is shifted 0.448 ft forward with respect to the default model. So, we first adjust the overall length and height to match our measurements from the previous steps:
Next, adjust the front overhang to 2.493 ft (the default vaue) + 0.448 ft (the offset) = 2.941 ft.
Once this is done, you will see the wheels appear back in the correct locations. We are not quite finished yet. The center-of-gravity ("cog") position remained fixed with respect to the Earth-frame even though you moved the front axle backward. You will need to adjust the "cog to front axle" back to maintain the same relative cog to front axle distance as the default SUV. The default SUV had cog to front axle = 4.364 ft. Simply enter this same distance for the new SUV:
Now you are finished. You can verify the overall dimensions, wheel, and cg placement by dropping another default SUV into the scene. Line up your police SUV and default SUV at x = 0, and yaw = 0, and display in side profile view and contour drawing mode. You should be see the two vehicles overlapping with good agreement:
Finally, delete all other objects in your scene. Move your police SUV to (x,y) = (0,0), set yaw = 0. Change the name of the vehicle as needed. Save your simulation as a .vc3 file. You can now drag and drop this file into any simulation for future use.
You can find our final .vc3 file here.
Note, you can use this same technique to modify a vehicle by addition any object, including primitive shapes. For example, in the case below, an ellipsoid (with level = 30) was used to model a modified box tube bumper bar. You can also add trailer hitches, or whatever else you need, by using this technique. See this video for example.
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