Create an Additional Mapping on a Display
A display comes with one mapping, and it fills the display. That is enough for most work — content lands on the screen and you never think about it.
A second mapping is how one physical screen serves content in more than one way. Each video channel chooses which mapping it renders through, so two channels can address the same display differently: one filling it, one placing content in a region, one following a wiring order that has nothing to do with either.
Surfaces work the same way. This page says "display" because that is the common case, but everything here applies to any scene object that carries mappings — including a surface blended across several projectors.
Before you start
- A display exists in the scene
- You know what the second mapping is for — a different content layout, or a wiring order that differs from the content order
Steps
1. Open the display's mapping controls
Select the display and find Mapping in the Inspector. Each existing mapping is one row: its name, then the buttons that act on it. The row marked * is the default.
2. Add the mapping
Three ways, depending on where you are starting from:
Control | Use it when |
|---|---|
The type dropdown, then Create | Starting fresh. Pick the type below the mapping list — Planar, Linear Fisheye to Equirectangular, Dome, Cylindrical, Cubic, Spherical or Frustum Projection — then click Create. For a display, planar is the normal choice — the others describe projection geometry a flat screen does not have. |
| The new mapping is a variation of the existing one. Faster than rebuilding, and it keeps you from disturbing the original. |
Import Mapping | The unwrap comes from a 3D file, authored outside Backstage. The model must have the same number of vertices as the object. |
A new mapping is not opened for editing on its own — click E on its row to start shaping it.
3. Name it for its job
A new mapping is named after its type and a number — Planar 2. Rename it in the Name field while it is being edited. Names are how you will tell them apart in the channel's Destination list, months later: "Full screen" and "Lower third" beat "Planar 1" and "Planar 2".
4. Shape it
Drag Mapping Position, Mapping Rotation and Mapping Size until content lands where you want it — or grab the mapping's gizmo in the Scene View, which is quicker when only a rough region is needed.
For a pixel-exact region on a flat screen, tick Pixel Values. The controls switch from metres to pixels: Total Canvas Size is the screen's full resolution, Sub-Canvas Size the size of the region, and Sub-Canvas Pos its top-left corner. Sub Aspect Ratio with its Set checkbox holds the region to a ratio while you type. This checkbox only appears for a planar mapping on a flat object — it is pixel arithmetic on a rectangle, so there is nothing for it to mean on a cylinder or a dome.
Then click Apply. Cancel discards the edit; Reset returns the mapping to its starting state.
5. Use it from a channel
In the Sequencer, select a video channel and open Destination. Every display and surface in the scene is listed with a checkbox. Tick the display, and a dropdown appears beside it holding that object's mappings — pick the new one rather than the default.
Done when: the channel's track in the Sequencer names both, as Display 1 : Planar 2, and the content has moved to where the new mapping puts it — while a channel still on the default mapping is unaffected.
The default mapping is not just "the first one"
One mapping on the display is marked the Default UV-Mapping, and that designation is load-bearing in two places beyond content:
Pre-slicing through Media Manager uses the default mapping. Change which mapping is default and you change what a pre-sliced media set is cut against.
The Pixel Map Raster pins which mapping's unwrap addresses the display's physical pixels — which is what lets you wire a wall along one unwrap while serving content through another.
So adding a mapping is safe; changing which one is default is not, on an installation that already relies on either of those. Black Level Correction places its result through the default mapping as well. The default is changed with the button at the left of a mapping's row.
Pin a Pixel Map Raster Mapping on a Display
Common Mistakes
The content did not move — the channel is still assigned to the old mapping. Adding a mapping changes nothing until a channel selects it.
Every channel moved, not just one — the default mapping was edited rather than the new one. Check which mapping is selected in the Inspector before dragging anything.
The shaping was lost — edit mode is not left implicitly, and saving the project does not apply it for you. Click Apply before selecting another object; anything left unapplied is discarded at the next Backstage restart.
A pre-sliced media set no longer lines up — the default mapping changed. Pre-slicing is cut against whichever mapping was default at the time.
The wall lights up in the wrong order — the Pixel Map Raster is pinned to a different mapping than you are serving content through. That decoupling is deliberate; check both.
A non-planar type on a flat screen behaves oddly — Dome, Cylindrical and Spherical mappings describe projection geometry. On a display, use planar unless you have a specific reason.
Related
Display — the Display reference: all mapping controls, plus splitting
Create a Sequence and Add Content — where a channel picks its mapping