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Elements can occur in more than one group. Groups are used in many parts of the Parameter Editor to specify which portions of input geometry you wish an operator to act upon.
You can also create ordered groups. To do so, enable the Ordered checkbox.
This operator is very powerful and is ideal for combining geometry that is similar. For example, all the primitive geometry of a group of door structures for a three-dimensional architectural model could be grouped together and consequently scaled and re-sized together using a Transform node. Works in conjunction with most filter nodes.
Group name specifiers become very powerful when you use pattern matching in your group specifiers.
Using Group Geometry
Creating groups based on point attributes
You can create groups based on point/primitive attributes using the Base Group tab and group specification syntax.
For example, to create a group containing all points with Y position greater than
In the parameter editor for the Group node, click the Base Group tab.
In the Base Group field (below Base Group), set value to
In this example,
P is the name of the position vector attribute,
.y takes the Y component of the vector, and
>0 selects points where the component is greater than 0. See the
@ group specification syntax for more information. Note that the
@ syntax does not allow spaces.
The geometry on which to create the groups.
Bounding geometry. (Only works for point or vertex groups when selecting by bounding geometry.)
Accepts all geometry.
The name of the group to create.
Whether to create a primitive, point, edge, or vertex group.
How to resolve collisions between the newly created group with an already existing group.
The newly created group will replace the existing group.
Union With Existing
The group will consist of the union between the newly created group and the already existing group.
Intersect With Existing
The group will consist of the intersection between the newly created group and the already existing group.
Subtract From Existing
The group will consist of the contents of the already existing group that are not also in the newly created group.
Enables grouping by pattern.
Enter the pattern to be grouped. This handles normal adhoc group syntax.
Orders the points/primitives in the group in the order they are entered. Useful when skinning.
What sort of primitives to allow in the group.
Keep in Bounding Regions
Enable grouping by bounding volume.
Shape of bounding volume.
Group by an axis aligned bounding box, specified either directly or by the second input.
Group by a sphere, either specified directly or by the second input.
Group points depending if they are inside the second input. Inside is determined with the alternating rule. Rays are sent and the number of intersections computed - if the result is odd, the point is considered inside. Because the rays are sent in a specific set of directions, if the geometry has holes you may get leaks that vary with the orientation.
Group points depending if they are inside the second input’s volumes or VDBs. This is determined by evaluating each volume or VDB at the point position and comparing with the isovalue. If the point is inside an odd number of volume or vdbs, it is considered to be inside.
Bounding Convex Hull
Group points depending if they are in the convex hull of the
points of the second input. This can be offset outwards or
inwards using the iso offset. The
pscale attribute is also
used to determine the effective size of points. If their
sphere is fully inside, they are considered to be inside. The
Include Partially Contained Entities can be used to instead
consider them inside if they at all touch the convex hull.
Size of bounding volume.
Center of bounding volume.
Initialize to Input Bounds
Set the Size and Center of the bounding box to the bounding box of the elements specified in Base Group or the full geometry if disabled.
The iso surface of volume to do the grouping with. Points whose volume value are less than this will be grouped. A value of 0 is good for SDF volumes. For fog volumes, use a value of 0.5 and turn on Invert Volumes for best results.
Inverts sense of being inside the volume.
Include Partially Contained Entities
When grouping primitives, include primitives that have at least one point in the bounding object. When grouping edges, include edges that have either point in the bounding object, or are intersecting the bounding object.
Keep by Normal
Enable grouping by normal. This is not yet supported for vertex groups.
Groups primitives facing away from this object.
Unlike grouping by normal this operation will remove items that satisfy the backface condition from any group created via another tab. If no other group is created, this operation will add satisfying items.
Groups polygons that are non-planar given the tolerance.
Polygons that are non-planar will be added to the group regardless of the other tabs.
Normal direction to group by.
Deviation from the direction to allow in the group.
Include by Edges
Points, primitives, and edges that match the edge grouping rules will be in the final group regardless of the other tabs.
Enables edge grouping. This is not yet supported for vertex groups.
Min Edge Angle
Groups primitives with at least this angle between their normals. For edge groups, an edge is included in the group if the two primitives that share it satisfy this angle requirement.
Max Edge Angle
Groups primitives with at most this angle between their normals. For edge groups, an edge is included in the group if the two primitives that share it satisfy this angle requirement.
Edge Angle Uses Angle Between Edges
For edge groups only, when this option is checked edges are included in the group based on the angle between themselves, instead of the angle between the primitives that share them.
Each edge is compared against all other edges that share a point with it.
Min Edge Length
Groups edges that have at least this length.
Max Edge Length
Groups edges that have at most this length.
Number of edges away from the points in Point Group.
Points around which group is centered.
Create Boundary Groups
Create groups containing surface boundary points.
Keep by Random Chance
Enables grouping by random chance.
The initial seed used to determine which elements are included in the group.
Use Seed Attribute
Whether to use an integer attribute on the specified elements that is used in place of the element number when determining whether an element is included in the group.
An integer attribute on the specified elements that is used in place of the element number when determining whether an element is included in the group. For edges, the point numbers or the attribute value on both points is combined and used to determine the seed for each edge. For vertices, the point number or attribute value on the point that the vertex belongs to is used to determine the seed for each vertex.
The approximate fraction of elements to include in the resulting group. The Global Seed is combined with the Seed Attribute or element number if Use Seed Attribute is disabled, to determine a seed value for each element. This seed value is then used to find a value between 0 and 100 for each element, and any element with a value less than or equal to the Percent is included in the group.