appearance.replaceWithContent

Replace one or many entities with a content asset — a bundle or mesh (a generated .bundle, a library asset, a primitive). Each target entity and its whole subtree is removed, and a fresh spawn of the content takes its slot: same parent, local position, rotation, and name; scale kept unless keepScale = false. Components on the removed entities do not carry over — the result is the content, not an upgraded copy of the target.

appearance.replaceWithContent("rider_blockout", "/zero/source/generated/meshes/a_snowboarder.bundle")
appearance.replaceWithContent({ "tree_1", "tree_2", "tree_3" }, "@libname::pine.bundle")
appearance.replaceWithContent({ "tree_1", "tree_2" }, "@libname::pine.bundle", { dryRun = true })

Targets are entity names or ids (one, or a list), scene.find records, or a query. dryRun = true resolves everything and returns the plan (which entities would be removed, how big each subtree is, what would spawn) without mutating, so a batch can be validated before it runs.

To swap an entity for another entity that already exists in the scene, use entityOps.swap. To change the mesh on existing entities without touching the entity itself, use appearance.setModel.