Texture2D.requestedMipmapLevel

Description

The mipmap level to load.

By default, the mipmap streaming system selects which mipmap to load based on the position of all Cameras. Setting this field forces a specific mipmap to be loaded and overrides the mipmap streaming system. The mipmap level can still be modified by budgeting memory. Use the streamingMipmapsPriority property to increase the chance of a particular Texture mipmap level being selected by the mipmap streaming system. The requested level is unaffected by minimumMipmapLevel

The value of requestedMipmapLevel is an exact mipmap level that ranges from 0 to the maximum mipmap level of the specific texture, or the Max Level Reduction value if that's lower. 0 is the highest resolution mipmap level.

The following example pins a texture to a specific requested mipmap level while the component is enabled, then hands control back to mipmap streaming when the component is disabled.

using UnityEngine;

public class PinRequestedMipmapLevel : MonoBehaviour
{
    // Avoid pinning the same texture multiple times.
    public Texture2D texture;

    // 0 is the highest-resolution mipmap level; higher values are lower resolution.
    public int mipmapLevel;

    void OnEnable()
    {
        // Request a specific mipmap level to load, overriding mipmap streaming.
        if (texture != null)
            texture.requestedMipmapLevel = mipmapLevel;
    }

    void OnDisable()
    {
        // Let mipmap streaming choose the level again.
        if (texture != null)
            texture.ClearRequestedMipmapLevel();
    }
}

Additional resources: ClearRequestedMipmapLevel, minimumMipmapLevel.