Choose a plate or 3D background by the camera move it must survive

Parallax exposes depth assumptions

When a camera translates, nearer objects shift against farther objects. A single flat image can maintain a convincing view from one position or for a tightly constrained move, but it cannot create independent depth motion that was not captured or built. That is why “it looks good in the viewport” is weak evidence for a moving shot. Write the proposed camera translation, rotation, lens change, foreground interaction, and focus behavior before choosing the background method.

Unreal’s Image Plate documentation describes plates attached to a Cine Camera frustum and automatically sized to its sensor dimensions. This can be exactly right for a locked-off or camera-relative element. It is not a promise of world depth. Similarly, the Media Plate stage guide recommends plane or sphere meshes for efficient 2D/360 playback; those mesh choices still define the geometry that the camera will see.

Classify the shot by geometry, not prestige

Test the worst intended motion

Build a short “geometry truth” test: the widest translation, closest foreground, fastest focus change, and longest lens that the shot intends to use. Watch through the production camera. Look for sliding horizon features, scale changes that reveal a plane, incorrect overlap, and inconsistent blur or reflection behavior. Epic’s Composure documentation notes that using a plate only as a 2D layer loses CG/media interactions; projected composite meshes are a different setup and still need lens matching for accurate compositing.

Illustrative example: a distant city plate can support an interior dialogue with a locked camera and practical window foreground. A lateral dolly may reveal a problem if nearby buildings in the plate should shift against the distant skyline but remain fixed within the same image. A very distant skyline can remain convincing; test the actual move rather than assuming a universal distance limit. The answer might be a restricted move, a multi-plane treatment, a projected proxy, or a 3D environment—not automatically a full rebuild.

Record the accepted limits

• State the approved camera volume and lens range, not merely “plate approved.”
• Describe any foreground, reflection, or focus limitation in the shot note.
• Keep an image from the worst accepted frame, not only the hero still.
• Retest when the edit changes the move, lens, or foreground blocking.

This is an Atlas proposed decision framework. It does not claim a universal motion threshold because apparent parallax depends on scene depth, lens, camera distance, and the audience’s reference cues.