---
title: Restricting access to specific mipmaps
framework: metal
role: article
role_heading: Article
path: metal/restricting-access-to-specific-mipmaps
---

# Restricting access to specific mipmaps

Set the range of mipmap levels that a sampler can access.

## Overview

Overview Sometimes, you want to control the specific mipmap levels that the sampler can read from. For example, you might do this when you haven’t provided texture data for all of the mipmaps, and you want to constrain access to the mipmaps that have data. You can configure a sampler to read from a subset of the texture’s mipmaps. Limit the sampler when you create it in your Metal app When you configure the MTLSamplerDescriptor instance, set the lodMinClamp and lodMaxClamp properties to the range of permitted values. This example creates a sampler that ignores mipmaps 0, 1, and 2. Limit the sampler when you create it in your shader If you create your sampler in your shader, specify the range of mipmap levels that it can access: constexpr sampler s(filter::linear, mip_filter::linear, lod_clamp(3.0f, MAXFLOAT)) Control mipmap selection when you sample the texture Some GPUs can apply additional constraints on the sample operation itself, passing in dynamic information about which mipmap levels the GPU can sample. Not all GPUs support clamping at the moment it samples a texture. Verify that GPU’s device instance supports clamping to a minimum level-of-detail (LOD) by checking whether it supports one of the following: The MTLGPUFamily.mac2 feature set. The MTLGPUFamily.apple6 feature set. In your shader, call one of the variants of the sample function that takes additional LOD parameters. For example, the following code limits sampling to a specific level or lower in the mipmap chain. The shader has a minimum level parameter that it uses to sample the texture: fragment float4 samplingShader(RasterizerData in [[stage_in]],                texture2d<half> colorTexture [[ texture(0) ]],                constant float &minimumLOD [[buffer(0)]]) {     constexpr sampler textureSampler (mag_filter::linear,                                       min_filter::linear,                                       mip_filter::linear);

const half4 colorSample = colorTexture.sample(textureSampler,                                                   in.textureCoordinate,                                                   min_lod_clamp(minimumLOD));          return float4(colorSample); } This example limits sampling to a specific level or lower in the mipmap chain. The shader has a minimum level parameter, minimumLOD, that it uses to sample the texture. The Metal Shading Language Guide describes other options for controlling mipmap selection. You can choose to sample a specific mipmap level, specify a minimum mipmap level, bias the selection process that the hardware chooses, or use some combination of these options.

## See Also

### Texture mipmapping

- [Improving texture sampling quality and performance with mipmaps](metal/improving-texture-sampling-quality-and-performance-with-mipmaps.md)
- [Creating a mipmapped texture](metal/creating-a-mipmapped-texture.md)
- [Copying data into or out of mipmaps](metal/copying-data-into-or-out-of-mipmaps.md)
- [Generating mipmap data](metal/generating-mipmap-data.md)
- [Adding mipmap filtering to samplers](metal/adding-mipmap-filtering-to-samplers.md)
- [Predicting which mips the GPU samples with level-of-detail queries](metal/predicting-which-mips-the-gpu-samples-with-level-of-detail-queries.md)
- [Dynamically adjusting texture level of detail](metal/dynamically-adjusting-texture-level-of-detail.md)