Collision is what prevents objects in your world from intersecting. Without collision, the player would be able to walk through the mesh. The collision box is also the first step to creating a hitbox around an asset you want to enable players to gather resources from. Geometry Collection Debug Draw
Existing Collision
Double-click your mesh in the Content Browser to open the Edit window.
If your mesh already has collision, you can view it by toggling Simple Collision in the Show menu of the static mesh editor.

If you want to delete the current collision, you can do this by going to Collision > Remove Collision.

Adding Simplified Collision
If your mesh does not have collision configured, you can easily add a simple shape around it.
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Double-click the static mesh thumbnail in the Content Browser to open the editor.
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In the Static Mesh Editor, expand the Collision dropdown menu and choose one of the top three options.
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The newly-created collision has a widget that you can use to translate, rotate, and scale your collision shape.
If you already have a collision on a mesh and you add another collision, the new one will not replace the previous collision, but add to it. Make sure to Remove Collision if you want to replace the previous collision.
Adding More Complex Collision
If you want your mesh to have more accurate collision, you can use the other options in the Collision dropdown menu.
K-DOP
These options are called the K-DOP simple collision generators. K-DOP is a type of bounding volume where K is the number of axis-aligned planes and DOP stands for discrete oriented polytope. It takes K axis-aligned planes and pushes them as close to the mesh as it can.
In the Static Mesh Editor K can be:
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10 - Box with 4 edges beveled - you can choose X- Y- or Z-aligned edges.
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18 - Box with all edges beveled.
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26 - Box with all edges and corners beveled.
Here is what the mesh looks like with 10-DOP, 18-DOP, and 26-DOP respectively.

Auto Convex Collision
When you select Auto Convex Collision from the Collision dropdown menu, you will see a Convex Decomposition panel appear on the bottom right corner of the editor.

Hull Count will generate as few primitives as possible to represent the collision mesh. Max Hull Verts increases or decreases the number of vertices your collision mesh has. The higher these values, the more precise your collision will be, but also the more complex and memory-hungry. Click Apply to apply changes.
Below is the result of having applied the values shown in the previous image.

Combining Simple Shapes
Another simple way to set up complex collisions is by using multiple simple shape collision meshes to create the collision for your mesh.
Add various Simplified Collision meshes and use the widget to translate, rotate, and scale the simple shapes into place.
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