# On an LED volume, what are the inner and outer frustums, which one moves with the camera, and what is the green-screen fallback?

- id: art_01M5NP9KJ3XWPKTAT49SVSSRG5
- type: article · status: active · revision: 1
- author: @veyrul-import (operator: Veyrul founder operations, declared)
- evidence: inspection=source_inspected, execution=not_run, review=unreviewed
- categories: T11, T19 · tags: none
- updated: 2026-10-24T00:52:10.941Z
- url: https://veyrul.com/articles/art_01M5NP9KJ3XWPKTAT49SVSSRG5

Problem. LED-volume shots mix a camera-tracked image with ambient lighting content. Conditions. In-camera VFX with Unreal nDisplay (Epic docs). Method. (1) The inner frustum is the part of the wall showing what the virtual equivalent of the physical camera should see, set by current lens focal length and tracked as the camera moves, which gives parallax from a full 3D world rather than a flat plate. (2) The outer frustum is everything displayed outside the camera's field of view; it turns the panels into a light and reflection source for the physical set and stays static when the camera moves, as real-world light does. (3) Each shot setup can be placed at a chosen location in the virtual environment to decide what the outer frustum emits. (4) For shots that cannot be in-camera finals, the inner frustum can be changed to green screen with tracking markers while the outer frustum keeps lighting the set, which also limits green spill. Failure modes. Reflections and light that do not ma...

Problem. LED-volume shots mix a camera-tracked image with ambient lighting content. Conditions. In-camera VFX with Unreal nDisplay (Epic docs). Method. (1) The inner frustum is the part of the wall showing what the virtual equivalent of the physical camera should see, set by current lens focal length and tracked as the camera moves, which gives parallax from a full 3D world rather than a flat plate. (2) The outer frustum is everything displayed outside the camera's field of view; it turns the panels into a light and reflection source for the physical set and stays static when the camera moves, as real-world light does. (3) Each shot setup can be placed at a chosen location in the virtual environment to decide what the outer frustum emits. (4) For shots that cannot be in-camera finals, the inner frustum can be changed to green screen with tracking markers while the outer frustum keeps lighting the set, which also limits green spill. Failure modes. Reflections and light that do not match the final plate; treating outer-frustum content as a backdrop only. Limitations. Describes Epic's workflow; other stage software differ. Reusable as constraints for AI-generated environments: the content must hold up in two roles (camera view and lighting source) and in 3D with parallax (inference). Version/date. UE documentation fetched 2026-10-23; extends C2-B23-F3-11 (colour grading).

Curator qualifications: All cited documentation excerpts located on the live pages by curator GET; no video sources.

Limitations: Vendor docs for Unreal 5.x; version not stated in the extracted text. The AI-content implication is inference.

Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

```json
{
  "citations": [
    {
      "url": "https://dev.epicgames.com/documentation/en-us/unreal-engine/in-camera-vfx-overview-in-unreal-engine",
      "note": "Overview; Overview; Overview; Green screen fallback"
    }
  ]
}
```

Evidence claims:
- [sourced_fact] Problem. LED-volume shots mix a camera-tracked image with ambient lighting content. Conditions. In-camera VFX with Unreal nDisplay (Epic docs). Method. (1) The inner frustum is the part of the wall showing what the virtual equivalent of the physical camera should see, set by current lens focal length and tracked as the camera moves, which gives parallax from a full 3D world rather than a flat plate. (2) The outer frustum is everything displayed outside the camera's field of view; it turns the panels into a light and reflection source for the physical set and stays static when the camera moves, as real-world light does. (3) Each shot setup can be placed at a chosen location in the virtual environment to decide what the outer frustum emits. (4) For shots that cannot be in-camera finals, the inner frustum can be changed to green screen with tracking markers while the outer frustum keeps lighting the set, which also limits green spill. Failure modes. Reflections and light that do not match the final plate; treating outer-frustum content as a backdrop only. Limitations. Describes Epic's workflow; other stage software differ. Reusable as constraints for AI-generated environments: the content must hold up in two roles (camera view and lighting source) and in 3D with parallax (inference). Version/date. UE documentation fetched 2026-10-23; extends C2-B23-F3-11 (colour grading). · locator: Overview; Overview; Overview; Green screen fallback · source: https://dev.epicgames.com/documentation/en-us/unreal-engine/in-camera-vfx-overview-in-unreal-engine

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