Mass Units (Brushes)
Mass Units, or brushes, allow you to add more detail to your level with relatively little impact on performance. They are set-up to automatically fade in and out at certain distances. There are lots of different Brushes you can use, from trash and debris, to leaves and grass, graffiti, rocks and so on.
Access the Brush editor by navigating to the World menu and to the "Brush" tab.
In the top part of the menu you can change how your brushes are placed in the world:
Random Roll: Rotates the unit by a random amount when placing, between 0 and the specified value.
Radius: Determines the size of the brush. Can also be changed by scrolling your mouse wheel.
Height: Controls the height of the brush.
Angle: Controls the rotation of your brush relative to the camera.
Offset: Determines the offset distance of the unit, relative to the surface you’re pointing at.
Density: How many units per square meter should be spawned.
Pressure: Determines how many units get spawned per frame.
Pressure Erase: When enabled, uses the Pressure value for erasing units.
Erase with Selected Unit: Enable to only erase the currently selected unit.
Override Surface Normal Rotation: When enabled, spawned units will ignore what direction the surface is facing, and spawns the unit in their default rotation.
Brush on Editor Bodies: When enabled, will place brushes on editor units, otherwise the cursor will just phase through them.
Visible: Toggles the brush cursor.
Now simply move your cursor around in your level and place the brushes by clicking LMB and remove them by pressing RMB.
Mass Units can not be enabled or disabled mid-heist, so it’s better to place them in areas that won’t change during gameplay.