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Unity LOD Groups

3 min read

Overview

LOD Groups let a 3D object swap between higher-detail and lower-detail versions as it occupies less screen space. In Unity, this is primarily a screen-relative workflow, not a pure distance-based one: the important question is how large the object appears in the camera view, because that is what determines whether extra mesh detail is still visible to the player. Unity’s recent optimisation guidance explicitly recommends LOD as part of cross-platform performance work, especially when the camera can see many 3D objects at once (Unity, Optimize Performance for Mobile, XR, and Web Games, see source-unity-performance-mobile-xr-web).

Setup

Typical workflow:

  1. Prepare at least two mesh versions of the same object.
  2. Add an LOD Group component to the parent object.
  3. Assign the detailed mesh to LOD0 and simpler meshes to later LOD slots.
  4. Adjust the transition markers in the LOD Group inspector.
  5. Test the object in the actual game camera, not just a loose Scene view.

Usage

Screen-space size vs physical distance

When students ask whether LOD should be based on physical distance or screen-space size, the better Unity answer is screen-space size.

  • A very large building can still fill a lot of the screen even when it is far away.
  • A very small prop can become visually unimportant while it is still quite close in world units.
  • Different camera FOV values also change how large an object appears.

So the practical rule is: tune LOD transitions around what the camera can meaningfully see, not around a fixed “10 metres means LOD1” mindset.

What LOD Bias changes

LOD Bias adjusts how aggressively Unity prefers higher-detail models.

  • Higher bias: detailed models stay visible for longer.
  • Lower bias: Unity switches to cheaper models sooner.

This is useful when different quality levels need different trade-offs. Unity’s URP material emphasises that quality settings and rendering choices are part of one connected workflow rather than separate knobs (Unity, Introduction to URP for Advanced Creators, see source-unity-urp-advanced-creators).

When to use LOD Cross Fade

Use LOD Cross Fade when popping between mesh versions is too obvious. It blends the transition so the change is less visually harsh. This is especially helpful on large environment props where the silhouette shift is noticeable.

Gotchas

  • Do not set transition points by guesswork alone. Test them in the real gameplay camera and target resolution.
  • LOD does not fix everything. If the material, shader, or lighting cost is the real problem, mesh swaps alone may not help enough.
  • Very aggressive LOD transitions can make objects shimmer or visibly “pop”.
  • Tiny props often do not need several LOD levels; the setup cost can outweigh the gain.

unity-urp-overview · unity-urp-lighting-and-render-features · unity-profiler · cinemachine-overview

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