Difforum · Echo Trails

Look at the promo GIFs on the Difforum README - the kaleidoscope renders, the cosmic spirals - and half their beauty is that the motion smears: bright shapes dragging soft comet tails across the frame instead of popping around discretely. That's long-exposure motion blur, and Difforum · Echo Trails is the node that makes it. It takes an IMAGE batch of frames and composites each frame over the accumulated history of the ones before it, with a decay that controls how long the ghosts linger. Motion trails, smooth and hypnotic, exactly the aesthetic the README's showcase clips lean on.

The mechanism is a running composite, and it's cheap: each output frame = the current frame mixed with a faded blend of everything that came before. The two knobs are all there is:

• decay (default 0.6, 0–0.99) - how fast old frames fade out. High decay (0.8+) means short, crisp trails; low decay (0.4) means long, smeary persistence where the whole clip starts to linger on screen. 0.99 is basically a light-painting camera with the shutter stuck open.
• mix (default 0.5, 0–1) - how much of the current frame vs. the trail history goes into the output. Lower mix = more trail dominance and a dreamier, more abstract result; higher mix = sharper source with a hint of ghosting.

Output: frames (IMAGE batch), same length in and out, ready for Flow Stabilize, grading, or Save Video.

Where it shines in the Difforum pipeline: after the Feedback Sampler or Live Sampler, before color/post. The README's own recipe for mesmerizing clips runs the kaleidoscope render through Echo Trails for "smooth motion blur." It also earns its place in the VJ footage path (Load Video → VJ Look → Echo Trails → Save Video) where it turns ordinary footage into the long-exposure VJ look with no model involved. And because decay can be scheduled conceptually - you don't get a schedule input here, but nothing stops you from running a short batch through it to taste-test the feel before committing.

Install

cd ComfyUI/custom_nodes
git clone https://github.com/chillithebillis/Difforum.git difforum

Restart ComfyUI ([Difforum] loaded N nodes) or ComfyUI Manager → "Difforum". numpy-only.

Common issues

• "It's just motion blur." Sort of - but it's temporal (frame-over-frame) rather than spatial (within a frame), which is why the trails move. If you want the within-frame bloom too, stack Glow or a blur after it.
• The image melts into a blob. decay too low, or mix too low - the history overwhelms the source. Nudge both up.
• Flicker in the trails. Echo Trails smooths flicker rather than causing it, but if your source frames have strong per-frame exposure jumps, the trail history carries the jump. Stabilize or grade the source first.

This is one of those nodes that's a single idea done well - two inputs, one output, no surprises. It's also the difference between a kaleidoscope clip that looks "technical" and one that looks expensive. Cheap on compute, heavy on vibe.