Meshes

Meshes make up a large part of your 3D worlds. Unity provides a modeling tool called ProBuilder and there are also some Asset storeA growing library of free and commercial assets created by Unity and members of the community. Offers a wide variety of assets, from textures, models and animations to whole project examples, tutorials and Editor extensions. More info
See in Glossary modeling plugins, such as 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
See in Glossary Deformer, UModeler, and Mesh Editor. And Unity has great interactivity with most 3D modeling software.

Unity supports triangulated or quadrangulated polygon Meshes, so you must convert Nurbs, Nurms, and Subdiv surfaces to polygons.

Colliders

Unity uses two main types of collidersAn invisible shape that is used to handle physical collisions for an object. A collider doesn’t need to be exactly the same shape as the object’s mesh - a rough approximation is often more efficient and indistinguishable in gameplay. More info
See in Glossary: Mesh CollidersA free-form collider component which accepts a mesh reference to define its collision surface shape. More info
See in Glossary and Primitive Colliders. Mesh Colliders are components that use imported Mesh data and Unity can use them for environment collisionA collision occurs when the physics engine detects that the colliders of two GameObjects make contact or overlap, when at least one has a Rigidbody component and is in motion. More info
See in Glossary. When you enable Generate Colliders on the Model tab, Unity automatically adds a Mesh collider when you add the Mesh to the SceneA Scene contains the environments and menus of your game. Think of each unique Scene file as a unique level. In each Scene, you place your environments, obstacles, and decorations, essentially designing and building your game in pieces. More info
See in Glossary so that the physics system considers it solid.

If you are moving the GameObjectThe 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
See in Glossary around (a car for example), you cannot use Mesh colliders. Instead, you will have to use Primitive colliders. In this case you should disable the Generate Colliders setting.

Hints

• Merge your Meshes together as much as possible. They should share Materials and Textures as much as possible. This has a huge performance benefit.

• If you need to set up your GameObjects further in Unity (adding physics, scripts or other components), make sure you name your GameObjects properly in your 3D application. Working with names like pCube17 or Box42 can be very difficult.

• Center your Meshes on the world origin in your 3D modeling application. This makes it easier to place them in Unity.

• If a Mesh does not have vertex colors, Unity automatically adds an array of all-white vertex colors to the Mesh the first time Unity renders it.

• The Unity Editor shows too many vertices or triangles (compared to the original Model in your 3D modeling application).

  This is correct. What you are looking at is the number of vertices/triangles actually being sent to the GPU for rendering. In addition to the case where the Material requires them to be sent twice, other things like hard-normals and non-contiguous UVs increase vertex/triangle counts significantly compared to what a 3D modeling application tells you. Triangles need to be contiguous in both 3D and UV space to form a strip, so when you have UV seams, degenerate triangles have to be made to form strips, which bumps up the count.