Houdini lets you “glue” disconnected RBD objects together. The objects
stay together until forces pulling them apart exceed the strength of the
There are two main workflows for using glue:
This feature is especially useful for breaking an object into chunks,
gluing them together, then colliding the glued object with another
object to make the glued object “shatter”.
A convenient way to create a shatter an object is to start with the
whole model and cut it up into chunks using the Cookie
SOP and a cutting surface such as a sphere (to
create smooth cuts), or a jagged polygonal surface.
Connect the results of each cookie to a Group SOP
to create the “chunk” groups. Then use a Merge SOP
to merge the resulting chunks together.
A useful way to create groups out of large numbers of disconnected
“chunks” of geometry is to use the Connectivity SOP
followed by the Partition SOP.
Connectivity creates an attribute (
class by default) and assigns
it a unique value each set of connective primitives or points.
You can then use Partition to make groups. In the Rule parameter,
enter a group name containing the
$CLASS variable, for example
|Glue one RBD object to another |
In the RBD object’s parameters, click the Glue tab. Set
the Glue to object field to the name of the RBD object you
want to glue this object to.
See how to create an RBD object for more
information on objects.
Set the Glue strength and Glue impulse half life to
control how much force is required to break apart the glued
objects. See the online help for the RBD Object
operator for information on these
|Set up chunked geometry |
In a Geometry object or SOP network, create the pieces of the
Assign the geometry of each piece to a group
Use meaningful names with a pattern (for example,
chunk_rightleg). This will let you pick out the groups using
the pattern parameter in the glue object.
Merge them together to create the final geometry.
|Import chunked geometry as glued-together RBD objects |
Use the tab menu to create an RBD Glue Object
In the glue object’s parameters, click the + button next to
the SOP path parameter and choose the SOP node or SOP
network containing the chunked geometry (see above).
Use the Group mask pattern to choose which groups to
import as pieces (for example
chunk*), or leave it as
use all groups.
Click the Internal Glue tab, and set the Glue strength
and Glue impulse half life to control how much force is
required to break apart the glued objects. See the online help
for the RBD Glue Object operator for
information on these options.