From first surface to Go Live

Projection mapping gets easier when the signal path is boring. Connect the projector first, then use your operating system to extend the desktop. Mirroring can work for a simple rehearsal, but an extended display gives the clean output window its own screen while the editor stays on the laptop.

Open Projektor in a modern browser. Chrome or Edge gives you the fullest display and WebMIDI support. Keep the projector awake, allow popups for the site, and make the browser window large enough to work comfortably. Projektor cannot discover or configure a projector at the operating-system level, so that connection must already exist.

Start with one quad surface and the built-in test pattern. A grid and crosshair reveal perspective errors much more clearly than finished footage. Select Warp mode with W, then drag the four corners until the projected rectangle follows the physical edges of the wall, panel, prop, or screen.

Use arrow keys for a one-pixel nudge and Shift plus an arrow for a ten-pixel move. Snapping can catch stage edges, centers, the optional grid, and corners from other surfaces. Hold Alt while dragging when you need to bypass a snap for one adjustment.

With the geometry stable, select the surface and choose a source. Projektor accepts image and video files, image URLs, a webcam, screen capture, live line-art camera, test patterns, and live GLSL shaders. Local files and camera sources stay on the current device. URL-backed media and shader code can travel with a shared project.

Use opacity and color controls to match the material you are projecting onto. Add and Screen are useful when black should read as the projector being off. Normal layers by opacity, Multiply darkens, and Lighten keeps the brighter contribution. A mask can trim a quad or ellipse without moving its mapped corners.

A Look snapshots the content and mix for each surface while leaving geometry in place. Capture the aligned state, give it a name you can recognize under pressure, and set a fade time. A zero-second fade is a hard cut; a longer value cross-dissolves the per-surface mix.

Even a one-Look project benefits from this checkpoint. It gives you a known state to recall after experimenting with opacity, shader code, or alternate media. For a small set, capture a safe blackout or low-intensity Look as well as the main visual.

Press Go Live to open a separate, chrome-free output window that mirrors the stage over a same-origin BroadcastChannel. If the browser exposes display selection and you grant permission, the menu can send that window directly to a chosen display. Otherwise, drag it to the extended projector screen and enter fullscreen there.

The output is a local companion to the editor, not a network stream. It must stay in the same browser profile and on the same machine. Closing it takes the session offline; the editor status reports when the window has closed.