When using keyframes or procedural generators or modifiers, such as Random, Noise, or Animator, any retiming operation will modify the interpolations produced by these tools.
The high precision of these interpolations allows Autograph to slow down any animation by creating new intermediate images, in order to maintain maximum smoothness; but, when you use a movie or an image sequence, you work with a finite number of images, played at a given framerate.
A 25 FPS movie will only have 25 images to play in one second. By default, if you use this source as a layer in a 25 FPS composition, each image of this comp will use one image of the movie; but, if you slow down this sequence, using a Speed Multiplier of 0.25 for example, Autograph will have to create new images to fill the gaps based on the previous and succeeding frames.
For this, three Retime Filters are available:
This is the simplest technique. The last complete frame provided by the reader is kept on-screen until the next one is required. Visually, this produces a more jerky animation but has the advantage of being based solely on existing frames.
Rather than keeping an image on-screen until the next one is used, it is possible to create a cross fade between these images in order to reduce the jerkiness of the Nearest mode; but, this option can be used even when no retiming is applied to the layer.
By selecting this option, a new section called Acceleration Motion-Blur appears.
The goal is to mix several images together by accumulation. We choose a Shutter Angle value, which will define a range of images to take into account before and after the current time. The higher this value, the further Autograph will search, upstream and downstream from the current time. Using the notion of Shutter Angle rather than a number of frames allows you to keep the same look, whatever the composition FPS.
We can define how many images within this range will be used during accumulation. The wider the range, the higher this value should be in order to smooth the animation.
Auto Shutter Angle:
This switch allows you to automatically calculate the shutter angle, based on the source framerate and the retiming applied to the layer.
Rather than just mixing existing images to produce new intermediate frames, Autograph is able to create new images based on movements between frames.
The image at the current time is compared to the next image, in order to detect how the pixels have moved from this image to the other. A second analysis is done in the other direction, from the next frame to the current one.
We obtain two sets of motion vectors, indicating the direction and the distance traveled by visible pixels in these two images. In addition to tracking pixels, these vectors are used to detect occlusions or the appearance of new elements, not present in the two frames.
From this information, Autograph can recreate as many intermediate images as necessary, depending on the remapping applied to the layer.
A warping deformation is applied to the current image to transform it into the second image. All that’s left is to determine how to fill the holes when elements are missing in between one of these two references.
There are two options:
Backward: The starting image is used to fill in the missing pixels, using the adjacent ones. Some of them can go in completely different directions, so strange deformations can appear; however, this method has the advantage of being quite fast during calculation.
Forward: A denser deformation grid where each subdivision is equal to one pixel is used and this time the destination image is used to fill in the missing pixels. Although it’s more intensive in terms of computation, this method generally yields better results.