Making a custom terrain in Unity

This tutorial explains how to make a custom terrain using Unity's built-in assets and textures and prefabs imported from the Asset Store.

1. In your Unity editor, create a terrain object by right clicking in your scene hierarchy and adding Terrain under 3D object.  

2. When you click the terrain you just created, you'll see an Inspector window on the right-hand side. Navigate to Terrain Settings in this window as in the screenshot below and adjust the size of your terrain, using Terrain Width, Length, and Height under Mesh Resolution.

3. To make your terrain look more realistic, you can raise and lower different parts of your terrain. Navigate to Paint Terrain and select "Raise or Lower Terrain" in the dropdown menu as in the screenshot below. You can raise parts of your terrain by moving your mouse while holding left click and lower parts of your terrain by moving your mouse while holding shift and left click.

4. To add texture to your terrain, navigate to Paint Texture in the dropdown menu. Then, under Terrain Layers, click the "Edit Terrain Layers..." button to add a new texture. You can either make your own terrain texture or import them from Unity's Asset Store. 

5. To make your terrain texture look more realistic, you can adjust settings for the terrain texture you just loaded. Click the texture you just loaded in Terrain Layers and scroll down to see texture-specific settings. 

Use sliders to adjust how reflective you want your texture to be (Metallic) and how smooth you want your texture to appear (Smoothness). 

You can also adjust Tiling Settings to set how many times you want your texture to be repeated throughout your terrain. For example, if your terrain size is 2000 by 2000, setting the Size component to 500 by 500 will result in your texture being repeated 4 times throughout your terrain.

6. Feel free to import and add prefabs like trees, bushes ... etc. from the Asset Store to make your terrain look more interesting!