Chromecast projection mapping: the three-second wall

The cheapest way to make a projector wireless is the Chromecast already gathering dust behind your TV. Plug it into the projector's HDMI port and the projector becomes a network display — which means a phone can map light onto your walls without a single cable run across the room. Here's how that works in practice with RoomCanvas, and what to reach for when you don't have a Chromecast at all.

The setup

1. Chromecast into the projector's HDMI port. Power it from the projector's USB jack if it has one.
2. Same Wi-Fi. Phone and Chromecast on the same network — that's the whole requirement.
3. One tap. Open the output screen and nearby devices appear by name. Tap yours; the wall is live in about three seconds, with no picker dialogs in the way.

What's actually happening

The phone doesn't stream a video file — it sends the scene: your mapped surfaces, their corner positions, and which look plays on each. The Chromecast renders the shaders itself as a live receiver, warped through the same projective math you set up when you fit the corners. That has two nice consequences:

• It keeps playing when you leave. Lock your phone, take a call, walk away — the receiver keeps rendering. The show doesn't stop because your screen did.
• Motion stays smooth. Looks run at the display's frame rate on the device itself rather than being compressed through a screen-mirror stream.

No Chromecast? Three other doors

AirPlay

Apple TV and AirPlay-capable projectors work the same one-tap way. Same network, pick the device, live in seconds.

HDMI cable

A USB-C-to-HDMI adapter is the zero-latency, zero-network option — useful at venues where Wi-Fi is hostile. The phone drives the projector directly as a second display.

Any browser

Every machine with a browser can be an output. The app shows a local link; open it on the laptop (or anything) plugged into the projector, full-screen it, done. No install on the far end, and nothing leaves your network.

Troubleshooting the usual suspects

• Device not found: same Wi-Fi network is the rule that's broken 90% of the time — guest networks and VLAN isolation block discovery. Rescan after switching.
• Light doesn't match the surface: that's a mapping fix, not a casting one — drag the numbered corners while watching the wall, or run a camera scan. Details in the support guide.
• Projector but no smart stick at all: the browser output above costs nothing to try tonight.

Privacy note, because it matters

Casting travels directly over your local network from phone to receiver. No cloud relay, no account, no analytics — the only thing that leaves your phone is the scene, and the only place it goes is the screen you chose. The privacy policy is short because there's genuinely nothing to disclose.

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How to projection map a wall with your phone → · Support & troubleshooting