Version: 2021.3
Creating shaders that support GPU instancing
Static batching

Draw call batching

Draw call batching is a draw call optimization method that combines meshes so that Unity can render them in fewer draw calls. Unity provides two built-in draw call batching methods:

  • Static batching: For static GameObjectsThe fundamental object in Unity scenes, which can represent characters, props, scenery, cameras, waypoints, and more. A GameObject’s functionality is defined by the Components attached to it. More info
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    , Unity combines them and renders them together.
  • Dynamic batching: For small enough meshes, this transforms their vertices on the CPU, groups similar vertices together, and renders them in one draw call.

Unity’s built-in draw call batching has several advantages over manually merging meshes; most notably, Unity can still cull meshes individually. However, it also has some downsides; static batching incurs memory and storage overhead, and dynamic batching incurs some CPU overhead.

Requirements and compatibility

This section includes information about the render pipelineA series of operations that take the contents of a Scene, and displays them on a screen. Unity lets you choose from pre-built render pipelines, or write your own. More info
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compatibility of Unity’s built-in draw call batching methods.

Render pipeline compatibility

Feature Built-in Render Pipeline Universal Render Pipeline (URP) High Definition Render Pipeline (HDRP) Custom Scriptable Render Pipeline (SRP)
Static Batching Yes Yes Yes Yes
Dynamic Batching Yes Yes No Yes

Using draw call batching

The following usage information is relevant for both static and dynamic batching. For information specific to each draw call batching method, such as how to enable and use each method, see Static batching and Dynamic batching.

Mesh RenderersA mesh component that takes the geometry from the Mesh Filter and renders it at the position defined by the object’s Transform component. More info
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, Trail RenderersA visual effect that lets you to make trails behind GameObjects in the Scene as they move. More info
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, Line RenderersA component that takes an array of two or more points in 3D space and draws a straight line between each one. You can use a single Line Renderer component to draw anything from a simple straight line to a complex spiral. More info
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, Particle SystemsA component that simulates fluid entities such as liquids, clouds and flames by generating and animating large numbers of small 2D images in the scene. More info
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, and Sprite RenderersA component that lets you display images as Sprites for use in both 2D and 3D scenes. More info
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are supported for draw call batching. Other types of rendering components, including Skinned MeshThe main graphics primitive of Unity. Meshes make up a large part of your 3D worlds. Unity supports triangulated or Quadrangulated polygon meshes. Nurbs, Nurms, Subdiv surfaces must be converted to polygons. More info
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Renderers Cloth, are not supported. Unity only batches Renderers with other Renderers of the same type; for example, Mesh Renderers with Mesh Renderers.

Unity batches draw calls of GameObjects that use the same material. This means to get the best results from draw call batching, share materials among as many GameObjects as possible. If you have two material assets that are identical apart from their textures, you can combine the textures into a single, larger texture. This process is called texture atlasing. For more information, see the Wikipedia article on texture atlasing. When textures are in the same atlas, you can use a single material asset instead.

In the Built-in Render Pipeline, you can use a MaterialPropertyBlock to change material properties without breaking draw call batching. The CPU still needs to make some render-state changes, but using a MaterialPropertyBlock is faster than using multiple materials. If your project uses a Scriptable Render Pipeline, don’t use a MaterialPropertyBlock because they remove SRP Batcher compatibility for the material.

Transparent shadersA program that runs on the GPU. More info
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often require Unity to render meshes in back-to-front order. To batch transparent meshes, Unity first orders them from back to front and then tries to batch them. Since Unity must render the meshes back-to-front, it often can’t batch as many transparent meshes as opaque meshes.

Unity can’t apply dynamic batching to GameObjects that contain mirroring in their Transform componentA Transform component determines the Position, Rotation, and Scale of each object in the scene. Every GameObject has a Transform. More info
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. For example, if one GameObject has a scale of 1 and another GameObject has a scale of –1, Unity can’t batch them together.

If you are not able to use draw call batching, manually combining meshes that are close to each other can be a good alternative. For more information on combining meshes, see Combining meshes.

Warning: When you access shared material properties from a C# script, make sure to use Renderer.sharedMaterial and not Renderer.material. Renderer.material creates a copy of the material and assigns the copy back to the Renderer. This stops Unity from batching the draw calls for that Renderer.

  • 2017–10–26 Page amended

  • Added note on dynamic batching being incompatible with graphics jobs in 2017.2

Creating shaders that support GPU instancing
Static batching