Creating our first rigidbody
The object of this tutorial is to create a cube and have it fall onto a plane. Start by creating a project, as we learned how to do in the first tutorial.
And just like that, your first project. I said we were going to have a cube fall onto a plane, so we need to put a plane in the scene. A plane is a simple geometric figure, a square.
Click "GameObject" in the menu bar, and select 3D Object -> Plane.
Now that we have the plane, we need to save the scene. Right-click on the blank area below the window that shows our new plane and select Create->Folder. This folder will contain all of the scenes for this project. This project only has one scene, but I prefer to keep them in a folder. I named mine "_Scenes", with an underscore to ensure that it is always the first item in the assets list.
Now, click File->Save Scene or press Ctrl+S (Command+S on a Mac) and save it under any name you would like in your "_Scenes" folder. I called mine "scene".
Now that we have saved our scene, create a cube in a similar manner to how we created the plane. Click GameObject->3D Object->Cube. The immediate problem that you will see is that the cube spawns inside the plane. To combat this, we need to change the Transform of the cube.
Change the Y (vertical) coordinate to 5, as shown in the photograph, and ensure that everything else in the Transform box is set as I have it. This will move the cube five metres vertically into the air, removing it from the plane.
Excellent! The problem has been solved, the cube is no longer inside the plane. Now, if we press the play button above the window with the cube and plane... nothing happens. The cube needs a Rigidbody in order to do anything.
Click "Add Component" in the Inspector on the right side of your screen, and type in the word "rigidbody". Press the Enter or Return key, and a Rigidbody will be added to the cube. We don't need to worry about mass, drag, and so on now, the only thing you need to check is that "Use Gravity" is checked and "Is Kinematic" is not checked.
Now, if we press the play button, the cube falls onto the plane, as shown in the red circle on my image, and this tutorial is complete.