Wheel appears to vibrate during movement only if mesh editor window is closed

Development Character & Animation
, , ,
1

Ok. I have something very weird happening with a wheeled vehicle. If I have the mesh editor window open on my second screen everything appears to work flawlessly. If I close the mesh editor window, the wheels appear to bounce. I found this on accident after completely rebuilding the blueprints multiple times. I have repeated the opening and closing of the window a lot to verify what I’m seeing.

If the mesh window is open, the wheels are fine. If the mesh editor window is closed, the wheels appear to bounce or vibrate on screen. The car body doesn’t move so suspension doesn’t seem to be vibrating just the visual appearance of the wheels.

Any ideas on what this is would be greatly appreciated.

Update: I have tested this on four more systems and they exhibit the exact same behavior. I have tested the vehicle demo from the marketplace and it exhibits the same visual problem.

In the first picture you can see the severe motion blurring around the wheel. The center of the wheel is rotating correctly around its origin and not bouncing. This motion blurring gets worse as the tire speed increases.

In the second picture, I opened the mesh editor window. As you can see there is no artifacts around the wheel. The speed of the vehicle is the same in both pictures.

192016-tire_motionblurred.png
192016-tire_motionblurred.png639×555 337 KB

192020-tire_not_motionblurred.png
192020-tire_not_motionblurred.png459×516 227 KB

2

Solution to motion blur issues for wheeled vehicles.

In the Double Wishbone Vehicle Tutorial they describe how to copy the data from the PhysX simulated wheels in the wheel handler node to the visual wheel bones. This method must be followed to be able to get correct motion blur on the wheels. For whatever reason when the WheelHandler copies the PhysX transforms to the skeleton bones something goes wrong and causes the distortion even when motion blur is not turned on in the camera. Whenever the mesh editor is open the motion blur for the entire system defaults to off or appears to. This is why when I had the mesh editor open the vibrations didn’t occur.

Even for standard wheeled vehicles not implementing wishbone suspensions this method fixes the visual errors by allowing you to control the motion blur being applied through the camera. Recommend that you turn on per bone motion blur in the vehicle mesh and the turn on motion blur in the camera with these settings.

Amount: 0.5 (default value: 0.5)
Max Size: 0.75 (default value: 5.0)
Per Object Size: 0.5 (default value: 0.5)

These values give us good results but may need to be tweaked for different cameras and meshes.