UE4中基于顶点数可视化排序Static Mesh的C++开发技术问询

Hey there! I’ve tackled similar mesh sorting tasks in UE4 before, so let’s walk through your questions clearly:

1. How to Link Vertex Count to 3D Position for Sorting #

The core idea is to associate each Static Mesh Actor with its vertex count, sort the actors based on this value, then map the sorted order to target 3D positions. Here’s a step-by-step breakdown with C++ specifics:

• Step 1: Collect Actors and Their Vertex Counts
  First, gather all the Static Mesh Actors you want to sort. For each actor, retrieve its vertex count (note: UE4 meshes have LODs, so you’ll usually want the highest-detail LOD’s vertex count):

  // Helper struct to hold actor and its vertex count
  struct MeshSortData
  {
      AStaticMeshActor* Actor;
      int32 VertexCount;
  };
  
  TArray<MeshSortData> MeshDataArray;
  
  // Iterate over all Static Mesh Actors in the level
  for (TActorIterator<AStaticMeshActor> It(GetWorld()); It; ++It)
  {
      AStaticMeshActor* MeshActor = *It;
      if (UStaticMesh* StaticMesh = MeshActor->GetStaticMeshComponent()->GetStaticMesh())
      {
          if (const FStaticMeshRenderData* RenderData = StaticMesh->GetRenderData())
          {
              // Get vertex count from the highest LOD (index 0)
              int32 VertexCount = RenderData->LODResources[0].NumVertices;
              MeshDataArray.Add({MeshActor, VertexCount});
          }
      }
  }
  

• Step 2: Sort the Collection by Vertex Count
  Use UE4’s sorting utilities to order the array by vertex count (ascending or descending):

  // Sort in ascending order (fewer vertices first)
  MeshDataArray.Sort([](const MeshSortData& A, const MeshSortData& B)
  {
      return A.VertexCount < B.VertexCount;
  });
  

• Step 3: Map Sorted Order to Target Positions
  Now, define a target position pattern (e.g., a straight line along the X-axis, a grid, etc.) and assign each sorted actor to its new position. For example, arranging actors in a line with 50 units of spacing:

  FVector StartPosition = FVector(-200.0f, 0.0f, 0.0f); // Starting point
  float Spacing = 50.0f; // Distance between each actor
  
  for (int32 i = 0; i < MeshDataArray.Num(); ++i)
  {
      AStaticMeshActor* Actor = MeshDataArray[i].Actor;
      FVector TargetPosition = StartPosition + FVector(i * Spacing, 0.0f, 0.0f);
      Actor->SetActorLocation(TargetPosition, false, nullptr, ETeleportType::TeleportPhysics);
  }
  

  You can adjust the position logic to use X/Y/Z axes, grids, or even custom curves based on your visualization needs.

2. Displacement Differences for Identical Meshes: Preset Positions or Dynamic? #

Your observation is spot-on—those differing displacements for identical chairs almost certainly mean target positions are pre-defined, not dynamically generated per vertex count alone. Here’s why and how it fits into your approach:

• Why preset positions? If you only sorted by vertex count, identical meshes would end up in adjacent (or even the same) positions. The large displacement differences suggest the system is using a pre-made list of target positions, and assigning sorted actors to these positions in order—regardless of whether their vertex counts match.
• Does this mean your思路 is偏差? No! Your core idea of sorting by vertex count is correct. You just need to account for a secondary assignment rule:
  • Option 1: Use a secondary sort key for identical vertex counts (e.g., actor ID, creation order, or original position) to break ties, then map to dynamic positions. This would keep identical meshes close but not overlapping.
  • Option 2: Pre-define a fixed set of target positions (like the ones in the reference video), sort actors by vertex count, then assign each sorted actor to the next position in the preset list. This explains why identical meshes end up far apart—they’re just taking the next available spot in the pre-planned layout.

Either way, your initial focus on vertex count as the primary sort criteria is perfectly aligned with the goal. The key is adding that extra layer to handle ties or match the preset visualization layout.

内容的提问来源于stack exchange，提问作者Lvcifer