my360place
Equirectangular, cubemap or HDRI
Three formats, one of which you almost certainly want.
A 360 image turns up in three shapes and the names get used interchangeably by people selling them, which is how you end up with a file that will not load into the thing you bought it for.
Equirectangular
One rectangle, always exactly twice as wide as it is tall. The whole sphere unrolled flat: longitude runs across, latitude runs down, and the poles are smeared along the top and bottom edges, which is why the sky in one always looks stretched when you view it flat.
This is the default. It is what Google Street View uses, what every tour builder imports, and what every game engine accepts. If a file is 2:1 you can be fairly confident it will work.
Cubemap
The same sphere as six square faces, like an unfolded box. Some engines prefer it because sampling a cube is cheap and there is no pole distortion. You rarely need to buy one: tools convert equirectangular to cubemap on import, and 3DVista, Pano2VR and Marzipano all do it for you.
HDRI
Not a different shape, a different amount of information. An HDR or EXR file is usually equirectangular too, but it stores brightness far beyond white, so a render engine can use the sky itself as the light in the scene.
This is the one people get wrong. A photograph of a bright sky saved as JPG is not an HDRI. It looks the same on screen and behaves completely differently the moment you light something with it.
How to tell before you buy
- Check the ratio. Not 2:1 and not six squares means somebody has cropped a panorama and is selling the crop.
- Check the extension. JPG and PNG are backgrounds. HDR and EXR are lights.
- Check the pixel width. Under about 4000 wide is fine on a monitor and visibly soft in a headset.
- Check whether it is one image or a set. One image is a backdrop. A set that matches is a location.
Everything in this catalogue is equirectangular JPG at 8192 x 4096, sold in matched sets rather than singles.
