Trail Blur is more or less a souped-up Motion Blur. I considered calling it Motion Blur+, but decided not to, since the default settings are quite different. The main extra feature is the ability to cause the blur to fade at the trailing end, giving a direction to the motion. That's something I've sometimes wanted that isn't available with Motion Blur. The other significant additional feature is the option of curved (circular) paths.
The plugin: Trail Blur.dll
Here is the UI:
The description from the Help menu:
Trail Blur creates a movement blur similar to the built-in Motion Blur effect, but with a number of additional options. The blur can fade away, and the blur's path can curve.
The controls are:
Angle: For straight blurs, the direction of motion. For curved blurs, the final direction of the motion.
Distance: The length of the blur, in pixels.
Curvature: The motion curvature. When 0, the motion is straight. When positive, the motion is clockwise. When negative, the motion is counterclockwise.
Shift: The blur's position. When 0, the motion ends at the original position. When 1, the motion begins at the original position.
Fade Amount: The maximum amount of fading. When 1, the path nearly disappears at the beginning of the motion. When 0, the blur does not fade.
Fade Profile (Linear to Exponential): The profile of the blur fade. When 0, the blur fades linearly. When 1, the blur fades exponentially.
Sample Spacing: The distance between blur samples. There are always an integer number of samples over the blur path. When 0, the number of samples equals the blur length, so the samples are one pixel apart. Positive values increase spacing, decreasing the number of samples. This can be used to produce multiple-exposure effects. Negative values decrease spacing, increasing the number of samples. This is sometimes useful for producing smoother blurs.
Brightness Enhancement: The amount to increase brightness. In some instances, particularly when used with black backgrounds, increasing the brightness can be used to counteract the decrease in brightness that results from spreading out pixels over long blurs.
Opacity Enhancement: The amount to increase opacity. In some instances, particularly when used with transparent backgrounds, increasing the opacity can be used to counteract the decrease in opacity that results from spreading out pixels over long blurs.
Clamp to Canvas: The method for treating off-canvas pixels. When unchecked, pixels that are outside the canvas do not affect the blurred image. When checked, outside pixels are included, and are considered to have the color of the border pixels. This option is mostly intended for backgrounds of constant color.
Some of the controls, such as the Brightness and Opacity Enhancements may be of delectable usefulness,
Though I'd normally have an antialias feature for this type of plugin, it's already slow enough for long blurs on large images, and setting the Sample Spacing control below 1 can often achieve a similar result.