Scatter on Volume

 

One of the features that makes Octane so powerful is the ability to handle a very large number of instances. Generating instances is usually done via third party tools which generate scatter data that can be imported into Octane.

The Scatter on volume node generates an arbitrary number of instances according to various patterns and distributes them in a volume (figure 1).

Scatter_On_Volume_Fig01_Houdini_v2021.JPG

Figure 1: The Scatter On Volume node used to scatter instances in a spherical volume shape

 

The Scatter on Volume node should be added to the MAT network. A Geometry node should be added to the OBJ network as the scatter object. It does not matter what is in this Geometry node as long as it contains a node that can have the Display flag enabled. The Octane Object Spare Parameters should be added to the scatter Geometry node (figure 2).

Scatter_On_Volume_Fig02_Houdini_v2021.JPG

Figure 2: Adding the Object Spare Parameters to the scatter Geometry node

 

The Scatter tab in the Object Spare Parameters is where all the connections are made for the scatter system to function properly (figure 3). The Scatter VOP node parameter should point to the Scatter on Volume node in the MAT network. The Scattered Object 1-4 parameter should point towards the objects to be scattered.

Scatter_On_Volume_Fig03_Houdini_v2021.JPG

Figure 3: The Scatter parameters required for Scatter on Volume to function properly

 

Scatter on Volume Parameters

Object Selection Method

The method for scattering the connected objects. The available scattering methods are Sequential, Random, and Selection Map.

 

Object Selection Seed

Seed value used to randomize the selection of source objects.

 

Dimension Determines the number of instances along each dimension (x,y,z).

 

Offsets

Determines the offset between the instances along each dimension (x,y,z).

 

Shape

Determines the shape of the volume in which the objects are scattered.

 

Culling Min

All instances in areas of the map that have a value below this threshold are removed.

 

Culling Max

All instances in areas of the map that have a value above this threshold are removed.

 

Orientation Priority

If the Up and Front Vector are not orthogonal, this parameter determines which one has priority.

 

Up Direction Mode

Selects between the use of a reference direction or a reference point. Reference point allows for finer (more localized) control over the orientation of the scatter objects.

 

Reference Up Direction

When Up mode is set to Direction, the reference up vector will point in this direction.

 

Reference Up Point

When Up mode is set to Point, the reference up vector will point towards this location.

 

Front Direction Mode

Selects between the use of a reference direction or a reference point for the front direction of the scattered objects.

 

Reference Front Direction

When Front mode is set to Direction, the reference front vector will point in this direction.

 

Reference Front Point

When Front mode is set to Point, the reference front vector will point towards this location.

 

Rotation Mode

Determines how the rotation parameters will affect the instanced geometry.

 

Rotation Min

Specifies the minimum rotation value for the instances.

 

Rotation Max

Specifies the maximum rotation value for the instances.

 

Rotation Step

When the Rotation mode is set to Random or Map and this parameter is non-zero, the values will be aliased to the nearest step.

 

Scale Mode

Determines how the scale parameters will affect the instanced geometry.

 

Scale Min

Specifies the minimum scale value for the instances.

 

Scale Max

Specifies the maximum scale value for the instances.

 

Scale Step

When the Scale mode is set to Random or Map and this parameter is non-zero, the values will be aliased to the nearest step.

 

Translation Mode

Determines how the translation parameters will affect the instanced geometry.

 

Translation Min

Specifies the minimum translation value for the instances.

 

Translation Max

Specifies the maximum translation value for the instances.

Translation Step

When the Translation mode is set to Random or Map and this parameter is non-zero, the values will be aliased to the nearest step.