Chaos Scatter is a powerful instancing and distribution tool that allows you to easily populate scenes with selected objects. This is especially useful for outdoor scenes that need to be filled with greenery, rocks, grass etc.

See the video for an example workflow.

To use Chaos Scatter within Maya, go to the V-Ray shelf and click the Chaos Scatter button.

Add your target object in the Targets Objects field. These are the objects that have models scattered over them.

Then, add the scattering object into the Models field - this is the model that scatters over.

You'll see the result immediately in the viewport.

Targets – Specifies the object(s), on which the instances are scattered.

Factors – This option is only available when On Surfaces scattering is set to Random distribution or the scattering mode is set to 3D - In Bounding Box. Determines how many instances are scattered on the currently selected Targets object(s).

Models – Specifies the objects which are scattered on the Targets object(s).

Frequencies – This option is only available when there are more than one Models objects. Determines the frequency of the currently selected instanced object in relativity to the others.

Enable – Enables scattering.

Scatter Type – Specifies in which mode scattering is applied.

1D - On Curves – Scattering mode where objects are scattered along curves. Open or closed curves can be used for this.
2D - On Surfaces – Scattering mode where objects are scattered on surfaces. It doesn't matter if the surface is horizontal, vertical or if it is part of a complex 3D object.
3D - In Bounding Box – Scattering mode where objects are scattered inside the object's bounding box. Keep in mind that bounding boxes are cube-shaped, therefore using this mode on a round object scatters instances in a cube around it. This mode is useful when scattering dust particles inside a room, fish in an aquarium, books on a bookshelf and similar.

Instance Count Limit – Limits the maximum number of instances. Note that this option does not determine how many instances are created. Instead it serves as a measure to avoid scattering too many instances and causing a crash.

Seed – Determines the random distribution used. Changing this value causes random permutations of the scattered objects(s).

Temporal Consistency – When enabled, instances are scattered in the selected Rest-pose Frame and stick to the surface, even if it gets deformed in other frames. Otherwise, instances get scattered in each frame separately and that might cause anomalies. Note that Temporal Consistency does not work in IPR yet.

Rest-pose Frame – Determines the initial frame, where the instances are scattered for all following frames. The specified frame with Rest-pose must correspond to the first frame of the animation.

Avoid Collisions – When enabled, instances that would collide with each other get discarded. This results in no overlaps between instances. Note that enabling this option might lower the number of instances.

Avoid Collisions Spacing – Controls the size of the bounding boxes used to detect collisions. Smaller values result in denser instances with some collision, higher values result in larger distances between instances. Values above 1 mean that the distance between objects is larger than their bounding boxes.

The options in this menu are active when the scattering mode is set to 1D - On Curves.

Spacing – Determines the spacing between instances in scene units.

Jitter – Randomly jitters instances along the spline. Each instance has Spacing applied on both its sides, except the instances at the end of the spline. The Jitter value is divided between those two Spacings. In order to allow instances to jitter in all their Spacing distance, the Jitter needs to be set to 2.

Offset – Determines how much the instances are offset in one direction of the spline. When set to 1, all instances replace the one after them, as the offset is equal to the whole value of the Spacing.

Follow Curve – Determines how scattered instances are oriented along the spline. Assigning a value of 1, makes instances follow the spline and are oriented along the local tangent direction.

The options in this rollout are active when the scattering mode is set to 2D - On Surfaces.

Distribution – Specifies the distribution mode of the objects.

Random distribution – This mode scatters instances randomly on all mesh objects. It is enabled by default.
UV Map – This mode uses UVW mapping to scatter instances in regular patterns.

Map Channel – Determines which UV map channel is used for the scattering when UV Map Distribution mode is selected.

Map Channel Name – Specifies the UV Map Channel name.

Count – Defines an exact number of instances to scatter - either overall, or per area in the case of scattering defined by density (Per Square option). The number is always limited by the Instance Count Limit option.

Per Square – When enabled, the number of instances to scatter is defined by density (Count per square having the given edge length). The number of instances is always limited by the Instance Count Limit option.

Square Size – The specified value is the edge length of a square defining an area for computing the scatter density. The length is measured in world units.

Density Texture – Allows a black and white texture map to be assigned. The map determines how the instances are scattered on the surface.

Pattern – Determines a pattern for the scattering.

Grid – Rectangular grid.
Running Grid – Rectangular grid with every other row offset by half of the grid spacing.
Hexagonal Grid – Arranges instances into hexagons.

Lock V – When enabled, the values of the V coordinate for Spacing, Jitter and Offset are locked to the U coordinate's values.

Spacing – Scales the pattern in UV space. When Spacing is set to 1, the pattern occupies the whole space. When Spacing is set to 0.5, the pattern is repeated twice.

Jitter – Determines what percentage of the instances are randomly placed. When Jitter is set to 0, all instances are placed according to the UVW mapping. When Jitter is set to 1, all instances are randomly placed.

Offset – Offsets the pattern by the given value. Keep in mind that 0 and 1 Offset gives the same result, as 1 moves the pattern by one whole repetition.

Slope Limitation limits scattering only to 'slopes' at certain angles. It can be used to create realistic spread of trees on curved surfaces, for instance. The lower the Angle range is set, the smaller the angle at which scattering stops.

Up Axis – The angles are measured either between the Local Up Axis and the surface normal, or the World Up Axis and the surface normal. You can select which up normal to use:

Local – When enabled, the Slope Limitation is measured according to the up vector of each individual Targets object.
World – When enabled, the Slope Limitation is measured according to the world Y-axis up vector for all Targets objects in the scene.

Min Angle/Max Angle – Defines a range of angles to which the scattering is limited. Instances outside of this range get filtered out.

The options in this rollout are active when the scattering mode is set to 3D - In bounding box.

Count – Defines an exact number of instances to scatter - either overall, or per a volume in the case of scattering defined by density (Per Cube). The number is always limited by the Instance Count Limit option.

Per Cube – When enabled, the number of instances to scatter is defined by density (Count per cube having the given edge length). The number of instances is always limited by the Instance Count Limit.

Cube Size – Specifies the edge length of the cube defining a volume for computing scattering density (Count, Per Cube). The length is measured in world units.

Moves the instances From the given distance To the given distance on the corresponding axis (in scene units). A Map can be attached. RGB maps can be used to control translations in specific axes (Red = X; Green = Y; Blue = Z). Grayscale maps control all axes proportionally.

Map Mode – Determines how the map is interpreted to control the translation.

Map Fixed – Black areas of the map represent the From values. White areas of the map represent the To values. No randomization occurs.
Random Amount – Black areas of the map do not have any randomization applied. In the white areas of the map full randomization occurs. The From and To values represent the lowest and highest translations allowed for the randomization.

Step – Determines a fixed distance by which all instances translate. If the values is left at zero, instances are translated continuously. Values greater than the difference between To and From result in all instances translating to the value of To.

Map Mode – Determined how the map is interpreted to control the rotation.

Map Fixed – Black areas of the map represent the From values. White areas of the map represent the To values. All values in between are on the grayscale spectrum. No randomization occurs.
Random Amount – Black areas of the map have no randomization applied. In white areas of the map full randomization occurs. The From and To values specify the lowest and highest rotation allowed for the randomization.

Step – Determines a fixed degree by which all instances rotate for the enabled axes. If the value is set to 0, instances are rotated continuously. Values greater than the difference between To and From result in all instances rotating to the value of To.

Normal Alignment – When a value different than 0 is entered, the instances are aligned according to the world Y axis. A value of 0 means the objects are following the target surfaces curve and 1 means they are fully upright along Y. This is useful when the Targets object is curved and the Models objects need to remain vertical, not follow the curve of the surface, e.g. trees on a mountain.

Preserve Model Rotation – When enabled, instances preserve the original rotation of the Instanced model object. Otherwise, the original rotation is ignored.

Scales the instances From the given value To the given value continuously. When Uniform Scaling is enabled, the X axis values are applied on the whole Distribute-on target object. A Map can be applied. RGB maps can be used to scale axes individually ( Red = X; Green = Y; Blue = Z). Grayscale maps control the scale of all axes proportionally.

Map Mode – Determines how the map is interpreted to control the scale.

Map Fixed – Black areas of the map represent the From values. White areas of the map represent the To values. All values in between are on the grayscale spectrum. No randomization is applied.
Random Amount – Black areas of the map have no randomization applied. In white areas of the map full randomization occurs. The From and To values represent the lowest and highest scale allowed for the randomization.

Step – Determines a value for scaling that is applied to all instances. Values greater than the difference between To and From result in all instances scaling to the value of To.

Uniform Scaling – When enabled, all instances in all axes are scaled according to the values of the X axis.

Preserve Model Scale – When enabled, instances preserve the original scale of the Models object.

Preview Type – Determines the way the instances are displayed in the viewport. This is not reflected when rendering.

None – Nothing is displayed in the viewport.
Point – Displays each instance as a point.
Wire Box – Displays each instance as a wireframe of a box.

Random Color by Model – Every model is assigned a random color, which is then used for every instance of that model.

Preview Instance Limit – Specifies the maximum number of instances displayed in the viewport.