Unity中切换剑模型MeshFilter时同步更新碰撞体的技术问询（含MeshCollider与BoxCollider需求）

Hey there! Let's break down how to fix your sword mesh and collider sync issue, plus switch to BoxColliders if that's what you prefer—since you mentioned being new to mesh-related operations, I'll keep things clear and step-by-step.

Fixing Your Current MeshCollider Implementation #

First, let's tweak your existing code to work correctly, since there's a small bug in the index wrap-around logic, and a quick note about MeshCollider behavior.

Corrected MeshCollider Code #

[SerializeField] MeshFilter sword; 
[SerializeField] MeshCollider swordCollider; 
[SerializeField] Mesh[] swordMeshes; // Renamed for clarity
private int currentMeshIndex = 0; 

public void ChangeSword() { 
    // Update the visible mesh
    sword.mesh = swordMeshes[currentMeshIndex]; 
    // Sync the collider to match the new mesh
    swordCollider.mesh = swordMeshes[currentMeshIndex]; 
    
    // Cycle to the next mesh (fix the wrap-around bug here)
    currentMeshIndex++; 
    if (currentMeshIndex >= swordMeshes.Length) { 
        currentMeshIndex = 0; 
    } 
}

Key Fixes & Notes #

• The original bug: currentmesh > mesh1.Length should be >= because array indices start at 0. For example, if you have 3 meshes, the last index is 2—when currentMeshIndex hits 3, it needs to reset to 0.
• If your sword moves or swings (dynamic object), make sure to check the Convex box on the MeshCollider in the Inspector. Unity doesn't allow non-convex MeshColliders on dynamic objects, so this is required for collisions to work properly.

Switching to BoxCollider (Better for Performance) #

MeshColliders can be heavy on performance, especially for fast-moving objects like swords. BoxColliders are lighter and easier to sync—here's how to make them adapt to each sword mesh:

Step 1: Update Your References #

Swap out the MeshCollider reference for a BoxCollider in your script:

[SerializeField] MeshFilter sword; 
[SerializeField] BoxCollider swordCollider; // Use BoxCollider instead
[SerializeField] Mesh[] swordMeshes; 
private int currentMeshIndex = 0; 

Step 2: Sync BoxCollider to Mesh #

When you switch meshes, calculate the mesh's bounding box (the smallest box that fits the entire mesh) and apply those values to the BoxCollider:

public void ChangeSword() { 
    // Grab the new mesh first
    Mesh newMesh = swordMeshes[currentMeshIndex];
    sword.mesh = newMesh; 

    // Get the mesh's local bounding box (size and center)
    Bounds meshBounds = newMesh.bounds; 

    // Adjust the BoxCollider to match the mesh
    swordCollider.center = meshBounds.center; 
    swordCollider.size = meshBounds.size; 

    // Cycle to the next mesh
    currentMeshIndex++; 
    if (currentMeshIndex >= swordMeshes.Length) { 
        currentMeshIndex = 0; 
    } 
}

What's Going On Here? #

• newMesh.bounds: This gives you the mesh's local-space bounding box—think of it as a "fit box" that wraps perfectly around the mesh.
• swordCollider.center: Aligns the collider's center with the mesh's center so they don't offset.
• swordCollider.size: Sets the collider's size to match the mesh's bounding box, ensuring it covers the sword's shape.

Extra Tips for Perfect Alignment #

• Make sure your sword model's parent object has a scale of (1,1,1). If the parent is scaled, the bounding box calculations will be off (since bounds uses local mesh space).
• If you want a tighter collider than the automatic bounding box, you can create arrays for custom sizes/centers (e.g., Vector3[] colliderSizes and Vector3[] colliderCenters), then assign them manually when switching meshes.

内容的提问来源于stack exchange，提问作者peleg siegel