1. Here's why

If you notice a red questionmark in one of your Projects, it means that the files for that model are missing in the Library folder.

The location of the Library folder depends on your version:

• Lumion 2023.x and newer: Documents/Lumion/Library
• Lumion 12.x: Documents/Lumion 12.0/Library
• Lumion 11.x: Documents/Lumion 11.0/Library
• Lumion 10.x: Documents/Lumion 10.0/Library
• Lumion 9.5: Documents/Lumion 9.3/Library
• Lumion 9.3.x: Documents/Lumion 9.3/Library
• Lumion 9.0.x: Documents/Lumion 9.0/Library
• Lumion 8.x: Documents/Lumion 8.0/Library
• Lumion 7.x: Documents/Lumion 7.0/Library
• Lumion 6.5: Documents/Lumion 6.5/Library

1.1: Lumion V11.3 and newer: Move the mouse cursor to the small circular Object Icon of the questionmark to see what the name of the missing model is.  Lumion will display the file name of the original Imported Model file.

1.1: Lumion 11.0 and older: Move the mouse cursor to the small circular Object Icon of the questionmark to see what the name of the missing model is.

Lumion displays the missing model name as ModelName.lib and there are up to 4 files per model that potentially are missing.

1.2: To get the missing model to appear again, please search for the missing files on your harddisk and network drives. If you find the missing files and they are the four Imported Model Library files, then move them to the Library folder and restart Lumion.

You should also check in the quarantine for the antivirus software on your PC and if there, try restoring them.

Where you have V11.3 or newer 

1.3: If you have saved a Project that contains a red questionmark model, it is not possible to move the files back to the Library folder in order to make the model appear again.

1.4: Instead, in the Imported Model browser window, select the model you want to replace the red questionmark with.

1.5: Lumion 9.0 and newer: Click on the Select button, and then click on the Object Icon of the red questionmark to select it. The Replace Selection button is located on the Object Panel in the top right corner of the Build Mode screen:

1.5.1: Lumion V11.3 and newer:

It is no longer possible to try using the Find in Library function (there is no Library Category for this object).

1.5.2: Lumion V9.0 to V11.3:

1.6: Lumion 8.5 and older: Click on the Context Menu button, and then click on the Object Icon of the red questionmark to select it:

1.7: Click on Selection -> Library... -> Replace with Library selection 

2. The following changes were made in V11.3:

• Missing file type icon in the Object Properties window.
• The missing model Placeholder keeps the original Position, Orientation, and Scale.
• The object is now locked and can’t be moved, rotated, scaled, or copied.
• Can be moved to other Layers.
• Shows the missing model file name.
• Links to a Knowledgebase support article.
• Is not able to be Grouped.
• ​It is no longer possible to try using the Find in Library function (there is no Library category for this object).
• Mouseover on Object Icon (node), will show the file name of the missing model.
• When saving a Project with missing files, the data is lost forever (but can be re-imported if you have the original file).
• The number of missing objects is listed in Lumion Performance Monitor.