Scatter surface node

Scatters new points randomly across a surface.

See also: Measure, Source

This node distributes new points across the surface in a roughly uniform pattern and attempts to limit clumping and holes.

You can use the generated points for a variety of purposes. They may be used to specify birthing locations for particles, template points for copying, or as queues for irradiance computations.

You can base the distribution of points on the surface area of faces (faces with a larger surface area will get more points), a user defined attribute, or a blend of area and attribute.

Note

This node scatters the points in UV (surface) space. That means surfaces with pinched sides (like NURBS spheres and cones) will have non-uniform distributions in 3D space.

Note

Volume primitives are handled differently. Points are scattered inside of them with a chance proportional to the field value inside them. Negative values are clamped to zero for this purpose.

Using Scatter

  1. Click the Display points icon in the display toolbar on the right side of the scene view.

  2. Select the object you want the points to scatter randomly across.

  3. Click the Scatter tool on the Model tab.

    Note

    Scatter replaces the surface of an object with a random points. However, you can turn on the Keep Original Geometry checkbox in the parameter editor or operation controls toolbar to keep the surface.

You can change the number of points in the parameter editor or operation controls toolbar.

Parameters

Group

Subset of geometry to consider when generating points.

Keep Original Geometry

Keep original geometry after scattering points

Compute Number of Points

Instead of scattering a fixed number of points, calculate the total area and use that as a scale on the points value. Note this total area includes the effects of any alternate attribute.

Number of Points

Number of points to scatter over the input geometry.

Points per Area

Number of points to scatter for every unit of area in the primitives.

Use Density for Volumes

Instead of using the surface area of the box that contains the primitive volume as the area, use the total non-zero component of the volume. This becomes a measure of volume rather than area, but matches expectations if one is measuring the amount of smoke in a primitive volume.

Scatter based on primitive area

Use the surface area of primitives to influence the distribution of points.

Alternate Attribute

An alterative attribute used to influence the distribution of points. This attribute can be either a point, primitive or vertex attribute. Lower attribute values will result in fewer points being generated, while higher values will result in more points being generated.

Attribute Bias

When an alternate attribute is specified, this determines how much of an effect the attribute has. A bias of 0 is equivalent to specifying no attribute at all (no effect), while a bias of one uses the attribute values exclusively.

Compute nearest points

After the points have been scattered on the surface, it is sometimes useful to determine how far apart the points are scattered (when using the points for irradiance computations for example). The mean distance to the nearest N points can be pre-computed and stored in a point attribute if this parameter is turned on.

Points to consider

The distance to the N the point will be stored in the attribute. For example, if a value of 4 is specified, the attribute will store the distance to the fourth nearest point.

Store in attribute

Name of the attribute to store the coverage distance.