The "Motion Blur" effect takes the image from the previous frame, blurs it, fades it by a specified amount, and draws this in the transparent areas of the layer. The end result is that items moving over a transparent background will leave a ghost behind them.
The caveats for this effect are implicit in the above description:
- The contents are slightly blurred, which (as shown in the image above) can cause static (and even slowly-moving) items to have a halo around them.
- Only the transparent regions are drawn to. If a moving object passes in front of another object on the same layer, there will be no motion trail passing over the object.
In the simple image shown above the blue ring is placed on a second Layer underneath the Layer with the motion blur effect applied. This both allows the 'needle' to leave a blur trail over top of the ring, and also prevents the ring from having a blurry blue halo around it.
Available under certain Qt licenses.
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