walking through objects

when i make an object for unity with blender such as a chair. when i import it to unity and press play my 3rd person controller walks straight through it which i dont want it to.

please can anyone help?

Okay,

What you need to do is to tick the "Generate Colliders". This can be found when you click on your model in your Project, in the Inspector Window. When you have ticked it, hit apply and your model should now have a physical form.

Adding a mesh collider (Component -> Physics -> Mesh Collider) should work as well