According to Autodesk’s Revit MEP User’s Guide (Revit MEP 2011, Chapter 17 “Electrical Systems”), lighting fixtures in Revit are hosted components—this means they rely on another model element (like a wall, ceiling, or floor) to exist. Specifically, ceiling-hosted lighting fixtures must be placed on a ceiling element that is within the same model file in which the light is being placed.
From the document:
“Most lighting fixtures are hosted components that must be placed on a host component (a ceiling or wall). To place a lighting fixture in a view:
In the Project Browser, expand Views (all) ➤ Floor Plans, and double-click the view where you want to place the lighting fixture.
Click Home tab ➤ Electrical panel ➤ Lighting Fixture.
In the Type Selector, select a fixture type.
On the ribbon, verify that Tag on Placement is selected to automatically tag the fixture.
Move the cursor over the drawing area.The lighting fixture is previewed as you move the cursor over a valid host or location in the drawing area.
Click to place the lighting fixture.”— Revit MEP User’s Guide, Chapter 17: Electrical Systems, p. 402
Additionally, in the Rendering section of the same guide, Autodesk clearly defines hosting relationships in lighting fixture templates:
“The names of all lighting fixture templates include the words Lighting Fixture. Be sure to select the appropriate template for the type of lighting fixture that you want to create. For example, to create a ceiling-based fixture for metric projects, use Metric Lighting Fixture ceiling based.rft.
Revit MEP opens the Family Editor. The template defines reference planes and a light source. For ceiling-based and wall-based fixtures, the template includes a ceiling or wall to host the fixture.”
— Revit MEP User’s Guide, Chapter 50: Rendering, p. 1148
This indicates that the ceiling host must physically exist within the same model environment. If the ceiling is part of a linked architectural model, the lighting fixture cannot attach to it directly because Revit does not allow cross-model hosting. In such cases, a work plane-based or face-based light family must be used instead.
Therefore, among the given options:
A (snapping using nodes) and B (hosted to a ceiling reference plane) are partial actions within a placement workflow, not hosting conditions.
C (defined in the ceiling layout pattern) is incorrect because pattern layout does not determine hosting.
D (placed in the same model as the ceiling) is correct since Revit requires the ceiling host and the light fixture to exist in the same project file for the hosting relationship to function.
Verified Reference Extracts from Revit for Electrical Design Documentation:
Autodesk Revit MEP User’s Guide (2011), Chapter 17: Electrical Systems, p. 402 — “Most lighting fixtures are hosted components that must be placed on a host component (a ceiling or wall).”
Autodesk Revit MEP User’s Guide (2011), Chapter 50: Rendering, p. 1148 — “For ceiling-based and wall-based fixtures, the template includes a ceiling or wall to host the fixture.”
Revit MEP Family Templates Description — Metric Lighting Fixture ceiling based.rft defines the ceiling as the hosting reference within the same model environment.
