Equirectangular to cubemap (and cubemap to equirectangular)

What a cubemap is and what it is for

A cubemap represents the surroundings with six square images, one per face of a cube: front, back, left, right, up and down. It is the format expected by 3D engines (Unity, Unreal, Godot, Three.js, Babylon), game skyboxes, reflection maps and many 360 viewers, because each face is a normal texture without the equirectangular's distortion at the poles.

How to convert an equirectangular to a cubemap

1. Choose the equirectangular panorama (2:1 JPG or PNG).
2. Pick the face size. The rule is the panorama's width divided by four: an 8192 px equirectangular gives 2048 px faces.
3. Download the six faces separately or as a ZIP named f, b, l, r, u, d (the Marzipano and krpano convention) or with your engine's naming.

And from cubemap to equirectangular

The reverse path is here too: choose the six faces and the tool stitches them into a single 2:1 panorama ready for any 360 viewer, for social media or for Andarama. Useful to recover a game skybox, a Blender render in cube format or a panorama from a camera that exports faces.

How it is computed

For every pixel of every face, a direction is traced from the centre of the cube, converted to longitude and latitude, and the matching point of the equirectangular is read. It is the same geometry Andarama's tiler uses to prepare tours, executed here on a Canvas inside your browser. No image is uploaded anywhere.