Chapter 11 | Touching Up the Polygon Mesh


Virtual CRASH 3 is an incredibly versatile accident reconstruction software package. With its large collection of vehicles, users are bound to find the right exemplar vehicle for their particular subject cases; however, occasionally as polygon meshes are resized and wheels are shifted to the appropriate positions to match subject vehicles, peculiarities may arise which can cause awkward looking final animations and visual aids. In this write-up we will discuss such a case which can occur when wheel positions are shifted away from the default exemplar vehicle model positions in order to match subject vehicle data. This can cause misalignment between wheel wells and the wheels themselves. Below, we will review how to correct this issue.

A video illustrating how to manipulate vehicle polygon meshes can be found below: 

Touching Up the Vehicle Mesh

In this example, when the wheel positions were adjusted away from the default model values, wheels shifted beyond the well location openings (see below). This is easily fixed in Virtual CRASH 3. First, switch your camera view to a profile projective view of your vehicle. In this particular example, the blue vehicle was oriented with yaw = -90 degrees, this making the “Front” camera give an orthographic view of the driver side.

Next, left-click on the “Vertices” selection type using the upper toolbar. This will allow you to modify the vertices within the mesh.

Next, left-click on the “Lasso Selection Region” tool (see below). This will allow you to circle the vertices you wish to adjust. Note, because the vehicle is in the orthographic view, by using the lasso tool to select our vertices, both the right and left side vertices will be selected at the same time; therefore, any modification made on one side is automatically mirrored on the other side.

Next, use the lasso tool to enclose the vertices around the edge of the wheel well:

We want to restrict the movement of our vertices along the y-axis in this case. This will prevent any unwanted lateral or vertical shifts. You can restrict the movement by using the upper toolbar and left-clicking on “Restrict to Y”:

Now place your cursor into “Select And Move” mode. You will then see a coordinate axis appear around your selected vertices. This is a movement grip.

Left-click on the horizontal arrow and hold, and then move your cursor to the left to shift the positions of the vertices (see below). You can also reselect the lasso tool, and using ctrl+left-click, lasso additional vertices to move along to the right should you see odd deformations develop as you shift your vertices.

Now you are done touching up your polygon mesh. Left-click on the “Object” selection type (to deselect “Vertices”), and reselect the “Move And Rotate” manipulator to continue editing your scene.

Tags: How to adjust wheel wells, modify polygons, modify vertices, customize mesh.

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