Mesh.SetIndexBufferData

Parameters

Description

Sets the data of the mesh's index buffer directly copied from data source.

This method does not update sub-mesh ranges or sub-mesh count. You must configure sub-meshes separately via SetSubMesh to define index ranges and topology, otherwise your mesh will not render.

By default, the data array is validated for out-of-bounds indices. To disable validation for additional performance, set the flags parameter to MeshUpdateFlags.DontValidateIndices. Only disable validation if you are certain your data is correct, as invalid indices can cause crashes or undefined behavior.

This is a high-performance, low-level method for populating mesh index data. It provides direct access to the underlying index buffer with minimal validation overhead, making it suitable for performance-critical scenarios where you need maximum control over mesh data.

For simpler ways to set indices that handle sub-mesh configuration automatically, use SetTriangles or SetIndices instead.

// Generates a procedural triangle mesh with 16-bit indices
// Attach this script to a GameObject and enter Play mode.

using Unity.Collections;
using UnityEngine;
using UnityEngine.Rendering;

[RequireComponent(typeof(MeshFilter), typeof(MeshRenderer))]
class SetIndexBufferParams : MonoBehaviour
{
    Mesh m_Mesh;

    void Start()
    {
        // Create mesh with predefined bounds to avoid recalculation
        m_Mesh = new Mesh
        {
            name = "SampleMesh",
            bounds = new Bounds(Vector3.zero, Vector3.one * 2f),
            vertices = new Vector3[] { new(-1f, 0f), new(0f, Mathf.Sqrt(2f)), new(1f, 0f) }
        };

        // Create and assign triangle indices
        using (var indices = new NativeArray<ushort>(new ushort[] { 0, 1, 2 }, Allocator.Temp))
        {
            // Configure index buffer format and allocate space
            m_Mesh.SetIndexBufferParams(indices.Length, IndexFormat.UInt16);

            // Assigns the generated indices to the mesh
            m_Mesh.SetIndexBufferData(indices, 0, 0, indices.Length);

            // Define single sub-mesh spanning all indices
            m_Mesh.SetSubMesh(0, new SubMeshDescriptor(0, indices.Length));
        }

        // Assign mesh to MeshFilter & MeshRenderer
        GetComponent<MeshFilter>().sharedMesh = m_Mesh;
        GetComponent<MeshRenderer>().material = GraphicsSettings.currentRenderPipeline != null ? GraphicsSettings.currentRenderPipeline.defaultMaterial : new Material(Shader.Find("Standard"));
    }

    void OnDestroy() => Destroy(m_Mesh);
}

Additional resources: SetIndexBufferParams, SetVertexBufferData, MeshUpdateFlags.