Grass

Инструмент — Paint Details. 

Edit Details>Add Grass Texture.
Для травы не требуются меши — только текстура.

Свойства:

Detail Texture	The texture to be used for the grass.
Min Width	Minimum width of each grass section in meters.
Max Width	Maximum width of each grass section in meters.
Min Height	Minimum height of each grass section in meters.
Max Height	Maximum height of each grass section in meters.
Noise Spread	The size of noise-generated clusters of grass. Lower numbers mean less noise.
Healthy Color	Color of healthy grass, prominent in the center of Noise Spread clusters.
Dry Color	Color of dry grass, prominent on the outer edges of Noise Spread clusters.
Grayscale Lighting	If enabled, grass textures will not be tinted by any colored light shining on the Terrain.
Lightmap Factor	How much the grass will be influenced by the Lightmap.
Billboard	If checked, this grass will always rotate to face the main Camera.

After you've clicked the Add button, you'll see the grass appear selectable in the Inspector.

Painting Grass

Рисуется так же, как деревья и текстуры.

Editing Grass

Можно изменить любые параметры импорта для текстуры дравы, выбрав Edit Details>Edit или кликнув по ней два раза. Откроется диалог Edit Grass.

Изменение всего нескольких параметров может существенно преобразить мир. Даже изменение Max/Min Width/Height сильно скажется на внешнем виде травы.