Wan Vace Keyframe Builder

If you've used Wan VACE for inbetweening - anchoring a video with reference frames you want the model to hit exactly - you know the chore. You build a frame sequence where real keyframes are punctuated by gray filler frames, then a matching mask sequence saying "preserve these, generate those." Do it by hand and it's a spreadsheet nightmare. The Wan Vace Keyframe Builder turns that whole job into one node with a visual UI: drop images in, position them on a frame timeline, and it emits the images and the synchronized masks.

This node got real community traction when it launched - the author's r/comfyui thread drew a score of ~59 with 21 comments, and the funniest comment was the honest one: Master Kijai already has a node for this, but you need one of his per separate frame, whereas this handles the whole sequence in one place. That's the pitch, and it's a good one.

How it works

You set frame_count (2–256) and the node builds a timeline. For each keyframe image you connect (image_1, image_2, … - dynamic, so the next input appears as you use the last) you give it a position (image_1_frame, 1 = first frame). Everything else is filler. The output is two batches that line up frame-for-frame: images with your keyframes at their positions and gray (0.5 - the VACE default) or green elsewhere, and masks where keyframes are 0 (preserve) and fillers are 1 (generate).

There's real control beyond the basics. auto_spacing distributes keyframes evenly for you, with spacing_type choosing the curve (linear, ease_in, ease_out, ease_in_out) and min_spacing enforcing a floor - the tooltip's warning is worth repeating: VACE typically needs 8+ frames between keyframes for good interpolation, and this node will respect that floor. background_images lets you swap the solid filler for an actual video or control sequence, wrapping if it's shorter than frame_count - which is how you'd drive the fill from pose data instead of flat gray.

Wiring it up

The keyframes and masks feed the VACE encoder - images → input_frames, masks → input_masks - and then on to the sampler. The one community failure mode on record: the original example workflow shipped with those two connections not wired, and people understandably got nothing but junk generations until the author pushed a fix. If your first run produces garbage, check those two sockets before anything else.

Troubleshooting

• Bad generations with keyframes connected → almost always the VACE encoder inputs not wired, per above.
• Keyframe drift → your gap is too tight; respect the 8-frame floor.
• Wan 2.1 vs 2.2 - the author confirmed it's used with 2.1; 2.2 VACE is expected to behave the same but is untested by the author, so test before you trust.
• Position off by one - positions are 1-indexed (1 = first frame), which trips people who think in zero-indexed batch coordinates.

Installing

Part of TrentNodes, under Trent/Keyframes. ComfyUI Manager → "Trent Nodes" → Install, or clone it:

cd ComfyUI/custom_nodes
git clone https://github.com/TrentHunter82/TrentNodes
cd TrentNodes
pip install -r requirements.txt

Restart after. If Manager flags the pack (a day-one repo rename left a registry duplicate it still distrusts), the manual clone is the reliable path.