Unreal Engine Issues

UE-79140

GenerateProxyMesh causes incorrect transform in ISM using Scale

GenerateProxyMesh causes incorrect transform in ISM using Scale

UDN
Description

MeshVertex has been converted by component transform before being converted by instance transform.
It is ( Vertex * ComponentTransform ) * InstanceTransform.

I thought it has to be converted by (Vertex * InstanceTransform * ComponentTransform).

I found one quick solution.

 

// code placeholder
 void FMeshMergeHelpers::ExpandInstances(const UInstancedStaticMeshComponent* InInstancedStaticMeshComponent, FMeshDescription& InOutRawMesh, TArray<FSectionInfo>& InOutSections)
 {
     FMeshDescription CombinedRawMesh;
 
     bool bFirstMesh = true;
     for(const FInstancedStaticMeshInstanceData& InstanceData : InInstancedStaticMeshComponent->PerInstanceSMData)
     {
         FMeshDescription InstanceRawMesh = InOutRawMesh;
 #if 0
         FMeshMergeHelpers::TransformRawMeshVertexData(FTransform(InstanceData.Transform), InstanceRawMesh);
 #else
         const FTransform ComponentTransform = InInstancedStaticMeshComponent->GetComponentTransform();
         const FTransform InstanceTransform = ComponentTransform.Inverse() * FTransform(InstanceData.Transform) * ComponentTransform;
         FMeshMergeHelpers::TransformRawMeshVertexData(InstanceTransform, InstanceRawMesh);
 #endif

 

Steps to Reproduce
  1. Put ISMs containing scaled instances and non-zero transform in the level. (see screenshot.)
  2. Enable HLOD in worldsetting pane
  3. Generate Proxy meshes in HLOD outliner
  4. Set Forced LoD level 0 in the HLOD outliner pane to display the meshes place a  wrong location.

 

[Image Removed]

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Fixed
ComponentUE - World Creation - Worldbuilding Tools - HLOD
Affects Versions4.23
Target Fix4.24
Fix Commit8211754
Main Commit8211754
Release Commit9552237
CreatedAug 20, 2019
ResolvedAug 23, 2019
UpdatedMar 30, 2021
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