Article Number: 31 | VC3 | VC4 | Post Date: March 14, 2017 | Last Updated: March, 14 2017
My imported vehicle doesn’t seem to have the correct width even though I set the width in the size menu. What am I doing wrong?
Whether you are importing a vehicle or making customizations to an existing vehicle in the database, on rare occasions, you may find that the vehicle width (excluding mirrors) appears to be different from your width setting in the size menu. If this occurs, this is likely due to features such as very large side mirrors or running boards. This is easy to correct in Virtual CRASH.
In the vehicle below, we added large running boards to our Toyota Tacoma pickup from the database and saved our modified model as a vcm.
When this new vcm is used to replace the default polygon mesh of the Tacoma, the width of the body no longer matches the intended dimensions specified in the size menu. This is apparent when looking at the pickup in the top-down orthographic projection. Here a red box, whose length and width are the proper dimensions of our truck, is placed beneath the pickup truck. The tires of the truck are seen to extend laterally beyond the truck’s body, and there are obvious gaps between the body and the sides of the red box. This is due to the running boards.
To correct this problem, simply go to the “exclude overlapping” menu in the left side control panel. By default this is set to 10% for the right and left side of the vehicle, to account for typical side view mirrors. Here we need to increase the values to account for the running boards as well. The exact value needed will depend on the the number of vertices that are used to model the lateral protrusion and the cross sectional area, but in this case increasing the overlapping parameters to 20% was sufficient to correct the truck’s width to the appropriate size by ignoring both the side mirrors and running boards in the width calculation, as shown below.
Note, the double red lines on the sides of the truck. The length between these lines is excluded from the width calculation.
In the case of right and left, the exclude overlapping algorithm is essentially specifying the number of vehicle model vertices to disregard in the width calculation, starting from the leftmost (or rightmost) vertex and moving inward along the vehicle’s local y-axis, where the percentage specified relates to the fraction of the total cross-sectional area (in the lateral projective view) that encloses those vertices.
You will find that the default setting of 10% excluding overlapping is sufficient to exclude side view mirrors in most cases.
Note, the impulse centroids for collisions are prevented from automatically being located within the excluded region of polygons specified by the exclude overalapping parameters. This generally prevents impulse vectors from being focused on soft vehicle components like side view mirrors. For example, in the case below, we can see in this t-bone impact, the impulse centroid is focused on the inner (non-excluded) volume of our pickup truck.
Depending on the nature of the case, you may wish to include the possibility of the impulse centroid automatically being focused within any region of your vehicle (for example running boards). In such cases, you may want to set the exclude overlapping value to 0% and tune the vehicle width using a template vehicle. This process was also illustrated in the blog post found here.
Below we see our template pickup truck in yellow and subject truck in black. With exclude overlapping set to 0% for our subject pickup, we tune the width until we see the body of our subject pickup correctly overlapping with our template pickup. The running boards are seen to protrude laterally beyond the specified width as expected.
Now that exclude overlapping is set to 0%, it is now possible for the impulse centroids to be automatically focused within any region of our pickup.
Of course, even with a non-zero exclude overlapping value specified, it is always possible to manually position the impulse centroid positions at any location by creating a user contact.
Tags: exclude overlapping, fixing width, size, left, right, top, bottom, front, back, wrong width
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