3D projection mapping at home: how to make a cube float in the corner of a room

3D projection mapping is what makes people stop and stare: light that looks like a solid object hanging in the air. In the clip beside this article there's no box in the room. It's a plain inside corner where two walls meet the ceiling, and a projector draws a cube into it. The grids fold into three faces, the front edge lands exactly on the real corner line, and from where the phone is filming the cube seems to stick out of the wall. Then the faces fill with moving patterns. All of it was mapped from an iPhone with EasyMapper Studio, with no laptop.

Here's how the illusion works, how to build it in your own room, and what to play on it.

3D projection mapping means fitting projected light to three-dimensional space so it looks like it belongs there. It comes in two flavours:

• Mapping onto real 3D objects. Every face of a real thing (a building, a box, a stack of pumpkins) gets its own layer, so the content wraps around the object. This is what you see on cathedrals and stages.
• 3D illusions on flat surfaces. A shape is drawn in perspective so that, from one viewpoint, it looks like it has depth. The corner cube in the clip is this kind.

Both use the same basic tool you'd use for any projection mapping: layers whose corners you drag onto real edges. The difference is only what you line those corners up with.

An inside corner is two walls meeting along a vertical line. A real cube seen from its front edge also shows a vertical line, with one face going back to the left and one going back to the right. If you draw the cube's front edge exactly on the corner line, your eye happily reads the two walls as the two side faces of a box.

The top face is what sells it. It's a diamond-shaped panel spanning both walls above the corner, and once it's there the brain stops seeing walls and starts seeing a solid block. Notice in the clip how the first two grids look like flat panels until the top appears.

The catch: the illusion is correct from roughly one spot, the place you stood (or the camera stood) when you shaped the faces. Walk well off to one side and the cube starts to look bent. For a room you'll mostly watch from the sofa or the doorway, that's fine. Shape it from there.

You need a projector that can reach the corner, an iPhone or iPad, and a dark room. Set the projector up facing the corner, connect your phone over HDMI or AirPlay (the connection guide shows the cables), then:

1. Map the left face. Add a layer and drag its four corners into a tall shape on the left wall, with its right edge running straight down the real corner line.
2. Map the right face. Add a second layer on the right wall that shares that same edge. The two layers' corners should meet exactly on the corner line.
3. Map the top face. Add a third layer above them as a diamond: its two lower corners sit on the top corners of the side faces, and the other two point up and back.

A grid on each layer while you work makes it easy to see when the edges line up and when the faces look the right size. Step back to your viewing spot often. If the cube looks squashed, make the side faces taller. If it looks like it's tipping forward, pull the top face's back corner lower.

Content that treats the three faces as one object works best:

• Matching patterns. Pixel grids, tiles and geometric shaders on all three faces at once, as in the clip, read instantly as a cube.
• A lighter top. Pick content for the top face that's a little brighter than the sides, the way a real box is lit from above. It deepens the illusion for free.
• Outlines. Bright lines along the cube's edges make a wireframe box, which looks great in a dark room.
• Your own videos. Anything in your camera roll can play on a face. Short loops that fill each face look better than footage with a horizon or text.

Changing the content on all three faces at once is what makes the cube feel alive. Each change in the clip looks like the box changing colour, not three screens switching.

Yes, and it's the other half of 3D projection mapping. Instead of faking a box, you map a real one: a stack of cardboard boxes, a pumpkin tower, a shelf, a sculpture. Each face that points at the projector gets its own layer, and the content follows the object's real shape.

The pumpkin projection mapping guide walks through mapping real pumpkins, and how to projection map a room covers turning a whole wall, TV and shelves into surfaces.

Do I need 3D software or a 3D model?

No. For a corner cube or a box you're only lining up flat faces, so dragging corners onto the real edges is all it takes. 3D modelling software matters for complex shapes like building facades, not for a cube in a room.

What projector do I need for 3D projection mapping at home?

Any projector with HDMI input, or one that supports AirPlay. In a dark room a small 500 to 1,000 lumen projector is enough for a corner. The projector guide covers what to look for.

Does it work on an outside corner?

Yes, and it's even easier. An outside corner, like a pillar or the corner of a building, already sticks out toward you, so its two walls are real side faces. Map one layer on each and the content wraps around the corner with no illusion needed.

How long does it take?

Shaping three faces takes a few minutes once the projector is in place. Most of the time goes into stepping back and nudging corners until the cube looks right from the sofa.

Find an empty corner tonight: open EasyMapper Studio, add three layers and build your first cube.