Multiplane Portals for the Metaverse

David A. Smith
3 min readJun 7, 2022

David A Smith and Vanessa Freudenberg

Multiplane Portals are a technique developed at Croquet Corporation for securely connecting 3D web-based worlds developed by different parties to create the Metaverse from independent microverses.

Multiplane portals solve a fundamental problem with linking web-based worlds in a secure and safe way. The ability to move freely and easily between the billions of virtual worlds in our future is a central pillar to the definition of the Metaverse.

But, you can’t simply load one world into another on the web. Even if you can technically do it, you have a host of challenges that you will never be able to address.

First and most important, some worlds will be infected by malware — the worst thing you can do is load some random code from the web into your own microverse page.

Second, different worlds may use totally different software stacks and rendering frameworks. There will not be a single standard for world interoperability, but at the same time, you do want to be able to view and traverse from one world to the next.

Third, worlds will be entered and exited dynamically. We will soon be meta-surfing where we move from one world to another without returning to the previous worlds. This means we need to dynamically remove the old worlds we visited reclaiming their resources.

The idea for multiplane portals combines the ability of iFrames to be rendered transparently with Disney’s original multiplane camera where they stacked transparent “cels” one on the other to achieve actual depth and opacity in an animated scene.

This enabled us to create portals using secure, sandboxed iFrames. Similar to how Disney used a multiplane camera for Snow White, multiplane portals use stacked iFrames. Portals are transparent “holes” in the top iFrames. The viewer can see through to the iFrames beneath.

Each iFrame in the stack is a different URL, which allows any Microverse world to connect via a live portal to virtually any other. A web app we call the shell is used to hold the stack of iFrames and allows them to communicate essential information.

This includes the spatial transform of the “from” portal and a viewport for clipping the rendering of the lower level worlds to the upper portal view. It can also include user info so that the world we are entering can load such things as the user’s avatar.

This is another example of the Croquet multiplane portals at work. The left hand side displays the two portals clearly — one on top of the other. Also, notice that when the user travers through the portal, the iFrames switch order so that the user is now “in” the new space.

Croquet will be publishing a more comprehensive description of the technology and our plan to make it available to support any web-based virtual world. Multiplane portals are implemented in the multiuser Croquet’s Microverse, implemented on the Croquet OS.

Sign up for our beta and try it out.



David A. Smith

AR, VR, AI, 3D Pioneer I invented 3D portals and crates in games. I wrote the first 3D adventure/shooter, and created Croquet - it redefines collaboration.