Twixtor

What you'll learn

This tutorial covers the full Twixtor pipeline for anime footage — from scene selection and framerate math to advanced techniques like Alt Motion Sources, FG/BG separation, and Guidance Masks. The workflow and theory are based on Lolligerjoj's blog post, which remains the definitive reference on the subject.

1 — Scene Selection & Fundamentals

Avoid Complex Morphs

Twixtor works by calculating motion vectors between frames — it tracks where each pixel moves and interpolates new frames from that data. This means scene selection is critical. Avoid clips with:

• Extreme shape-shifting (e.g. transformations, morphing effects)
• Heavy colour changes between frames (e.g. flashing lights, colour washes)
• Chaotic or incoherent movement with no clear direction

These will produce unfixable warping artefacts regardless of any settings you adjust downstream.

The Lolligerjoj Philosophy

Anime is typically animated on "2s" or "3s" — a single drawing held for 2 or 3 frames rather than a new drawing every frame. At 23.976 fps this means the actual animation update rate is around 8–12 fps. If you apply Twixtor directly to a raw anime clip without accounting for this, it will interpolate between identical static frames and produce massive, blocky glitches. Every technique in this tutorial exists to work around that fundamental mismatch.

2 — Framerate Calculation & Pre-Comping

Calculate the Interval

Step through your footage frame by frame and count how often the drawing actually changes. Common values:

• Every 2 frames → animation on 2s
• Every 3 frames → animation on 3s

The Math

Take your composition framerate (usually 23.976 fps) and divide by the interval:

Enter the result into Twixtor's Input: Frame Rate setting. This tells the plugin how fast the animation is actually moving, so it interpolates between real drawing changes instead of static holds.

Workflow

Always isolate your clip first, pre-compose it, and trim the pre-comp precisely to the start and end of the clip. A loose pre-comp with handles outside your cut will confuse Twixtor's vector calculation at the boundaries.

3 — Handling Inconsistent Framerates

Forcing Constant Animation

Sometimes anime mixes intervals within a single cut — a drawing holds for 1 frame, then 3, then 2. Twixtor cannot handle variable update rates cleanly. You have to force the animation to update on every single frame before it ever sees the clip.

Time Remapping Hack

1. Enable Time Remapping on your clip layer.
2. Step through the clip and set a keyframe on every frame where the drawing changes.
3. Manually drag those keyframes together in the timeline so the clip updates at a constant rate — one new drawing per frame.

Pre-comp and Twixtor

Pre-compose this forced-animation layer. Now apply Twixtor to the pre-comp using your native framerate as the Input Frame Rate. Time-remap the outer pre-comp to stretch the clip to the duration you want. Twixtor now sees a consistent input and can interpolate cleanly.

4 — Image Prep & Alt Source Motion Layers

Contrast is Key

Twixtor tracks pixels by contrast. If a dark shadow moves across a dark jacket, there is not enough contrast for the plugin to follow the edge — it will lose track and warp. The solution is to feed it an artificially high-contrast version of the problem area without actually rendering it into your comp.

Creating a High-Contrast Matte

1. Duplicate your footage layer.
2. Use Roto Brush to isolate the problem region (a sleeve, a limb, a piece of clothing).
3. Apply Curves and crush the colours until the region is a highly saturated, clearly separated shape against its background.

The result will look terrible. That is intentional.

Alt Motion Source

Hide the ugly high-contrast layer, then go into Twixtor's settings and assign it to the Alt Motion Source drop-down. Twixtor uses this hidden layer to calculate motion vectors — the accurate vectors get applied to your original, clean footage. The viewer never sees the matte; they only benefit from it.

5 — Guiding Edges with Tracking Points

Fixing Micro-Warping

For small, localised glitches — a collar shifting, a sleeve bending slightly wrong — Twixtor's built-in Tracking Points are the right tool. The plugin provides up to 12 points that you can keyframe manually.

Manual Tracking

1. Place a Tracking Point on the problem edge in the first frame.
2. Step through frame by frame and reposition the point to follow that edge exactly.
3. Assign the point to the correct layer type (Main Background in most cases) inside the plugin settings.

This guides Twixtor's vector solver along the exact path those pixels are actually travelling, eliminating the micro-warp without requiring a full matte.

6 — Foreground / Background Separation (Matte Layers)

The Core of Advanced Twixtoring

When objects overlap in 2D space — a character moving behind a static crate, a hand passing in front of a face — Twixtor cannot distinguish between them. It treats the entire frame as one surface and tries to pull background pixels into the foreground's motion path. The result is a smearing or ghosting artefact along the overlap edge.

Frame-by-Frame Masking

You must separate the overlapping objects manually:

1. Duplicate your clip for each object that overlaps.
2. Mask each duplicate to isolate only its object using the Pen tool.
3. Step through every frame of the overlap and adjust the mask so it follows the object accurately.

Hierarchy

Establish a clear layer order:

• FG1 — the object closest to the camera
• FG2 — the next object behind it
• Main Background — everything behind both

Twixtor processes each layer's motion vectors independently and composites them back together, eliminating the smear.

7 — Creating Guidance / Motion Masks

Large-Scale Tracking

Instead of using tiny Tracking Points, you can draw a loose, rough mask around an entire moving object — a floating bubble, a projectile, a character crossing the frame. This mask acts as a large-scale guidance vector that steers the plugin's solver across the whole object at once.

The mask does not need to be precise. A rough outline is enough; Twixtor uses it as a direction hint, not a pixel-perfect matte.

Opacity Keyframing

If the guided object exits the frame mid-clip, you must keyframe the mask's opacity from 100% to 0% as it leaves. If you do not, Twixtor will continue attempting to track a non-existent object and corrupt the surrounding pixels. This is one of the most common causes of unexplained artefacts in an otherwise clean setup.

8 — Assigning Layers in Twixtor

Mapping the Data

After creating all your mattes — FG1, FG2, Alt Motion Source layers, and Guidance Masks — none of them do anything until you tell Twixtor what they are.

Open the Twixtor plugin settings and assign each layer to its corresponding drop-down:

• Main Background — your primary clip (or the background separation layer)
• FG1 — your first foreground matte layer
• FG2 — your second foreground matte layer
• Alt Motion Source — your high-contrast matte layer

Twixtor processes each stream separately, then recombines them into a single output with accurate, separated motion vectors per object. Without these assignments, all your masking work has no effect.

9 — The Final Polish: CC Force Motion Blur

Why Not RSMB

Both Lolligerjoj's blog and this video explicitly advise against using ReelSmart Motion Blur (RSMB) directly after Twixtor. RSMB calculates its own independent motion vectors from the rendered output. These vectors frequently conflict with the carefully constructed Twixtor vectors underneath — especially near the FG/BG separation edges — and can reintroduce smearing artefacts that your masking work already eliminated.

CC Force Motion Blur

Instead, use After Effects' built-in CC Force Motion Blur effect. It works by rendering the interpolated frames multiple times at slight time offsets, then blending them — a brute-force approach that creates a natural, organic blur without running any additional vector analysis.

Recommended settings:

Higher sample counts produce cleaner blur at the cost of render time. At 8 samples, CC Force Motion Blur reliably hides any remaining micro-warping artefacts from even an imperfect Twixtor setup.