# Multi-Screen Output Drive several displays from one patch, each showing its own part of the composition — a projector panorama, a video wall, or a stage rig where every surface gets its own slice. Multi-screen output is part of **Cloude Plus**, and it runs in the **desktop app**: a screen is a real, borderless, fullscreen OS window placed on a chosen display, which the browser cannot open. --- ## The idea in one paragraph Every screen renders the **same composition**. What differs is the **region** — the crop of the composition that screen shows. A single mirrored output is the full region; three projectors across a wall are three thirds. The editor broadcasts the composition's state (the shader, the uniforms, the compute graph) **once**, and each output window re-renders it and presents its own part. That is why the second and third screen cost the editor almost nothing: no pixels are copied between windows, and no work is repeated on the editor's side. --- ## Setting up a rig **View → Output Screens…** opens the screens panel. 1. Pick a layout: **Single**, **2 across**, **3 across**, **2 stacked**, or **2 × 2**. The rig is built with a screen per tile, named for its place. **Mirror** is the other wall — it keeps the rig you have and points every screen at the whole composition, so the same image goes to every projector. 2. Assign each screen a display. **Auto** takes the next display the editor is not on and no other screen has claimed, so "3 across" lands on three projectors without any picking at all. 3. **View → Open Output** (`Ctrl/⌘ + Shift + 2`) takes the whole rig live. The layout map at the top of the panel draws the composition once with every screen's region on it. Overlaps show as a brighter band and gaps show as bare background, which is the quickest way to see that a wall is actually covered. ### The fields | Field | What it does | | --- | --- | | **●/○** | Switches the screen on or off. Off keeps the screen in the rig without holding a window open. | | **Name** | What the screen is called, in the panel and in its window title. | | **Display** | Which display it opens on. `Auto` = the next free one. | | **Resolution** | How many pixels the screen *presents* with. The render is always the output format. | | **Region X/Y/W/H** | The part of the composition this screen shows, in percent. | --- ## Edge blending Two projectors aimed at one wall have to overlap, and the overlap has to fade out on both sides or the seam reads as a bright bar. 1. Set **Edge blend** in the panel before choosing a layout. At 10%, each tile shares a tenth of its width with its neighbour, and the tiles still cover the composition exactly. 2. Give each screen's surface a **soft edge** in the projection-mapping panel (**View → Projection Mapping**). The feather runs the fade that makes the two beams add back up to one continuous image. --- ## Framing and mapping together Both a region and a projection mapping crop the composition, and they compose in the obvious order: **the region decides what the screen shows, and the mapping works inside it.** A surface pinned to the left half of a screen samples the left half of that screen's region — not the left half of the whole composition — so a mapping set up against one projector keeps meaning the same thing when the rig is re-tiled around it. The mapping itself is composition-wide: every screen warps through the same surfaces, each folding in its own framing. --- ## Resolution A screen renders the whole composition and shows a crop of it, so the render behind a crop is **larger** than the display: a third of a composition presented on a 1920-wide projector is rendered 5760 wide, or the crop would be a 3× upscale of a 1920 frame. That is the honest cost of driving a wall from one machine, and it is what keeps a panorama sharp. The **Resolution** field caps the pixels a screen *presents* with, not what it renders — useful when the GPU is the bottleneck. The render is letterboxed into whatever that yields, so framing never changes with it. Very steep crops are clamped to what the GPU will allocate (8192 px on the long edge), scaling both axes together so the picture's shape is never squashed. --- ## Saving a rig The screens travel with the project: displays, framing, names and resolutions. Whether a projector is *live* does not — a rig loads switched off, so opening a patch to look at it never throws windows onto whatever happens to be plugged in. Press **Open Output** to go live. --- ## Notes for a show - **Esc** on an output window closes that screen alone, and the rig records it as off — the next region nudge will not reopen it. - **F** or double-click toggles that window's fullscreen; **P** shows its performance overlay. - The editor's render loop is capped to a fixed 60fps while any screen is open, so a high-refresh editor display cannot over-drive the shared GPU. - Closing what is already open is never gated: an entitlement that lapses mid-show cannot strand a window on a projector. - Every screen is a full second render on the same GPU. A rig is limited to eight screens, and the shared device is the practical ceiling long before that. --- ## Troubleshooting **A screen opened as a small window with a title bar.** It had no display left to take — either every display is already claimed or the machine has only one. Assign it a display explicitly in the panel. **A screen shows the whole composition instead of its slice.** The output window could not create a WebGL2 context, which is what applies the crop. It falls back to mirroring rather than going black. **A saved rig points at a display that is not connected.** The assignment is kept and shown as "not connected". Plug the display back in, or reassign the screen. --- ## See also - [Projection Mapping](GEOMETRY_MAPPING.md) — corner-pinning onto physical surfaces - [Dual Screen Setup](dual-screen.md) — the WebSocket streaming path, for remote displays - [Frame Rate & Display Refresh](frame-rate.md)