# Create collision shapes for a sprite

> Generate or create the shapes that Unity uses to determine if a sprite collides with other sprites.

In a 2D project, Unity uses collision geometry to determine if a sprite collides with other sprites. Collision geometry can be one shape, for example a circle around the sprite, or a set of multiple shapes.

You can do either of the following:

* Generate collision geometry automatically.
* Create default custom collision geometry for all instances of a sprite.

## Generate collision geometry automatically

Follow these steps:

1. From the **Project** window, drag the sprite asset () into the scene.
2. In the Editor window of the sprite GameObject, select **Add Component**.
3. Select **Physics 2D**, then a [**Collider 2D**](/engine/6000.5/manual/unity2d/2d-physics/collider-2d.md) component.

If you select **Polygon Collider 2D**, by default Unity tries to create collision geometry that encompasses the opaque parts of the sprite.

Unity displays the collision geometry as a green outline in the Scene view. To edit the collision geometry, refer to the [Edit the collision geometry for one instance](#edit-the-collision-shape-for-one-instance) section.

## Create default collision geometry for all instances of a sprite

To create custom collision geometry that Unity uses every time you create an instance of a sprite, use the **Custom Physics Shape** tab of the **Sprite Editor** window and a **Polygon Collider 2D** component.

Follow these steps:

1. In the **Hierarchy** window, select the sprite GameObject.

2. In the **Inspector** window, in the Editor component, select **Open Sprite Editor**.

3. Select the **Custom Physics Shape** tab in the top-left dropdown. Unity displays the **Outline Tools** overlay.

4. Select **Generate** to automatically generate an outline that follows the opaque parts of the sprite. Unity displays the outline in white. Each point is a vertex of a collision shape.

   You can also create one or more outlines manually by clicking the sprite then dragging a rectangle.

5. Edit the geometry if you need to. For more information, refer to [Custom Physics Shape tab reference for the Sprite Editor window](/engine/6000.5/manual/unity2d/sprite/sprite-editor-window-reference/custom-physics-shape-editor-reference.md).

   To change how closely the geometry follows the opaque parts of the sprite, adjust the **Outline Detail** and **Alpha Tolerance** properties, then regenerate the outline.

6. To save the geometry, select **Apply** in the toolbar.

7. Add the sprite to the scene.

8. In the **Inspector** window of the sprite GameObject, select **Add Component**, then **Physics 2D** > **Polygon Collider 2D**.


**Left: Automatically generated geometry with a low Outline Detail value. Right: Automatically generated geometry with a higher Outline Detail value.:**
![](/api/media?file=/engine/6000.5/media/images/2DCustomOutline_7.png)

Unity now uses the collision geometry for all new instances of the sprite if you add a **Polygon Collider 2D** component.

> **Note:**
>
> Unity doesn't automatically update existing GameObjects with the collision geometry. To update an existing **Polygon Collider 2D** component, right-click the title of the collider component in the **Inspector** window, then select **Reset**.

For more information, refer to [Custom Physics Shape tab reference for the Sprite Editor window](/engine/6000.5/manual/unity2d/sprite/sprite-editor-window-reference/custom-physics-shape-editor-reference.md).

## Edit the collision geometry for one instance of a sprite

To edit the auto-generated collision geometry of a single sprite instance, or override the collision geometry from the **Custom Physics Shape** tab, use the **Edit Collider** 
**Frame:**
![](/api/media?file=/engine/6000.5/media/images/edit-collider-inspector-icon.png) button.

Follow these steps:

1. In the **Hierarchy** window, select the sprite GameObject.
2. Select **Edit Collider** (
   **Frame:**
   ![](/api/media?file=/engine/6000.5/media/images/edit-collider-inspector-icon.png)). The **Edit Collider** button is also available in the [Tools overlay](/engine/6000.5/manual/working-with-scenes/scenes-manage-gameobjects/overlays/reference/default.md) of the Scene view.

To edit the geometry, do the following:

* To move a point, select and drag it.
* To add a point, click on an edge.
* To remove a point, hold Ctrl (macOS: Cmd) while hovering over an edge, then select a red edge.
* To exit the editing mode, select **Edit Collider** again.

> **Note:**
>
> Editing the collision geometry of a single instance doesn't change the collision geometry in the **Custom Physics Shape** tab of the **Sprite Editor** window.

## Additional resources

* [Sprite Editor window reference](/engine/6000.5/manual/unity2d/sprite/sprite-editor-window-reference.md)