Unreal Engine Issues

UE-219819

Cannot instantiate an InstancedStaticMesh component with ConstructionScript

Cannot instantiate an InstancedStaticMesh component with ConstructionScript

Description

Starting with Unreal Engine 5.4, the logic for adding ISM instances by adding ISM components in the Construction Script (like below) has failed. 

[Image Removed]

This issue accidentally was introduced at CL28594968. From this change, UInstancedStaticMeshComponent::CreateSceneProxy() started to early-return with null in the above repro scenario, due to a new flag bInsInstanceDataApplyCompleted.

Steps to Reproduce
  1. Download the repro project, ISMIssue54.zip, and unzip it.
  2. Open the project.
  3. Open ConstSrcTest from the content browser.
  4. Click BP_ConstTest from Outliner.
  5. Change Default > Static Mesh in the Details panel.
  6. Confirm the displaying mesh disappers.

Expected Behavior: The mesh chosen at step 5 appears (technically as an ISM instance)

Workaround in this repro project: Turn off and on Default > Generate flag to run ConstructionScript again.

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Fixed
ComponentUE - Graphics Features
Affects Versions5.4
Target Fix5.5
Fix Commit35017787
CreatedJul 21, 2024
ResolvedJul 23, 2024
UpdatedJul 30, 2024
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