While using the default ground plane to create ground reflections is fast and simple, creating a custom ground plane is extremely easy and will give you more control over your scene. Use this is as starting point and also experiment with using different material types to represent your ground for even more unique ground planes.
1. Add a Ground Plane
To start, go to the edit menu, and select Add Geometry, Ground Plane. This will add a simple plane at the origin. Resize the plane to fit your scene.
2. Adjust the Ground Material Options
The Ground Material is unique in that it has no diffuse color. Instead, this Material Type takes on the color or visuals of your background settings so no edges are visible. Double-click on the part to adjust the following options:
This setting is simillar to the setting found in the Project, Environment tab, and will set the color of shadows cast on this plane.
This is where you set how reflective your ground is. Click on the color swatch to open the color picker window. You can tint the reflection cast by selecting a color, but to retain true mirroring of colors make sure you select a grayscale color. (You can make this easier by selecting Grayscale in the color mode pulldown. Choose values that are lighter to make them more reflective, or choose values that are darker to make them less reflective.
This slider is similar to the roughness slider in other materials. As you increase roughness, you will see the reflection become more blurred, like in a matte finish.
Clip Geometry Below Ground
Enable this option to cut off any part of your model that rests below the ground plane. This is useful with cars or vehicles to simulate the flattening of the rubber tire as the weight of the vehicle pushes it against the ground.