Editing > Timewarps > Blending Timewarped Frames >

# Blending Frames Using a Pretrail or Posttrail

With trails, you have greater control over how frames are blended. You can add a trail to the image that precedes or follows the object:

- A pretrail mixes the frames that follow the current frame with the current frame. In the final clip, the image trail precedes the object.
- A posttrail mixes the frames that precede the current frame with the current frame. In the final clip, the image trail follows the object.

Pretrail mix | No mix | Posttrail mix

The number of frames used in the mix is set with the pretrail and posttrail timing curves. Since you can change the shape of the timing curves, the trail values can be varied in the clip. When you use a pretrail or a posttrail, the mix value is not used.

To add a constant pretrail or a posttrail to an element in the timeline:

1. Select an element in the timeline and add a Timewarp soft effect.
2. In the Timewarp quick menu, select Trail from the Timewarp Processing option box.

   The Trail fields appears.

   (a) Timewarp Processing option box (b) Pretrail Weight field (c) Posttrail Weight field

3. Set the pretrail or posttrail value in the corresponding field.
4. Set the fall-off value for the trail in the Weight field. The Pre and Post field each have one Weight field to their right.
   - When the Weight is set to 100%, there is no fall-off. The first image in the trail has the same intensity as the image in the current frame.
   - When the Weight is set to 0%, the image in the current frame is at 100% intensity and the first image in the trail is at 0% intensity.

To add an animatable pretrail or a posttrail to a clip in the Timewarp Editor:

1. Select an element in the timeline and apply a Timewarp soft effect.
2. Click E beside the Timewarp soft effect button.
3. Open the Trail folder in the Timewarp Editor.
4. Select the PreTrail and/or the PostTrail option.

   (a) PreTrail and PostTrail options

   The channel for the selected trail appears in the Timewarp Editor.

5. Use the Animation controls to set the timing curve for the trail by adding and moving points on the curve.
6. Set the fall-off value for the trail in the Weight channel. Each PreTrail and PostTrail channel has one Weight channel.
7. Click the button in the Player to preview the result of applying the trail curve to the source clip.
8. When you are satisfied with the results, click Process to process the clip.
   NoteIf your timewarp contains trail values, you can preview the result in the Player without rendering by using the Preview FX mode.