F**k machine compositor

A browser tool for compositing 3D models (`*.glb`) onto photos.

Line a model up with an object in a photo and save the result as an APNG or GIF.
Alignment works by pinning points on the model to points on the photo and minimizing the reprojection error, which can also estimate the camera's focal length and principal point.

Usage

1. Load a photo and a 3D model

Use "Open photo" and "Open glb".
Default assets are loaded at startup, so you can try things out right away.

2. Line the model up

In "Align" mode: left drag to rotate, right drag to translate, wheel to scale.

For a precise fit, use handles. "+ Add handle" places a point in model space; drag it in the preview onto the matching point in the photo and the pose satisfying those constraints is solved with the Levenberg-Marquardt method. Three constraints pin the pose down, and with four or more you can also let the focal length f be estimated.

3. Paint the parts you want masked

Painted areas in "Mask" mode hide the model and reveal the photo, which is how you tuck the model behind something in the foreground. Lowering "Strength" cuts it out only partially, leaving the model semi-transparent.

4. Save the result

"Save APNG" writes an APNG at the photo's resolution (a PNG if there is no animation).
GIF is available too, but it drops to 256 colours and the file ends up larger than the APNG.

Switching to "Preview" mode before saving hides the handles and other overlays, so you see exactly what will be written out.