Unity sorts Renderers according to a priority order that depends on their types and usages. You can specify the render order of Renderers through their Render Queue. In general, there are two main queues: the Opaque queue and the Transparent queue. 2D Renderers are mainly within the Transparent queue, and include the Sprite Renderer, Tilemap Renderer, and Sprite Shape Renderer types.
2D Renderers within the Transparent Queue generally follow the priority order below:
There are other factors which can cause the sorting order to differ from the regular priority order. These factors vary from project to project.
The Sorting Layer and Order in Layer (in the Renderer’s Property settings) are available to all 2D Renderers through the Inspector window or via the Unity Scripting API. Set the Renderer to an existing Sorting Layer or create a new one to determine its priority in the rendering queue. Change the value of the Order in Layer to set the Renderer’s priority among other Renderers within the same Sorting Layer.
You can specify the Render Queue type of the Renderer in its Material settings or in the Shader settings of its Material. This is useful for grouping and sorting Renderers which are using different Materials. Refer to documentation on ShaderLab: SubShader Tags for more details.
The Camera component sorts Renderers based on its Projection setting. The two options are Perspective and Orthographic.
In this mode, the sorting distance of a Renderer is the direct distance of the Renderer from the Camera’s position.
The sorting distance of a Renderer is the distance between the position of the Renderer and the Camera along the Camera’s view direction. For the default 2D setting, this is along the (0, 0, 1) axis.
When you set the Camera component to Perspective or Orthographic, Unity automatically sets the Camera’s TransparencySortMode to match the selected mode. You can set the Transparency Sort Mode manually in two ways:
The Camera Transparency Sort Mode settings are under the Graphics category in the Project Settings (main menu: Edit > Project Settings > Graphics). When this is set to Default, a Camera component’s Projection setting take priority. When this is set to an option other than Default, the Camera component’s Projection setting remains the same, but the Camera’s Transparency Sort Mode changes to that option.
An additional option available through the Project settings and via the Scripting API is the Custom Axis sort mode.
Select this mode to sort Renderers based on their distance along the custom axis you set in the Project settings (main menu: Edit > Projecting Settings > Graphics > Transparency Sort Axis). This is commonly used in projects with Isometric Tilemaps to sort and render the Tile Sprites correctly on the Tilemap. Refer to Creating an Isometric Tilemap for further information.
By default, a Sprite’s Sort Point is set to its Center, and Unity measures the distance between the camera’s Transform position and the Center of the Sprite to determine their render order during sorting. An alternate option is to set a Sprite’s Sort Point to its Pivot position in World Space. Select the Pivot option in the Sprite’s Sprite Renderer property settings and edit the Sprite’s Pivot position in the Sprite Editor.
The Sorting Group is a component that groups Renderers which share a common root together for sorting purposes. All Renderers within the same Sorting Group share the same Sorting Layer, Order in Layer, and Distance to Camera. Refer to documentation on the Sorting Group component and its settings for more details.
Unity sorts Renderers with the same Material settings together for more efficient rendering performance, such as with dynamic batching.
When multiple Renderers have identical sorting priority, the tiebreaker is the order that Unity places the Renderers in the Render Queue. Because this is an internal process that you have no control over, you should use the sorting options (such as Sorting Layers and Sorting Groups) to make sure all Renderers have distinct sorting priorities.