Manually Creating Glue Constraints in Houdini

Download Houdini File: Destruction Manually create Glue and Spring Constraints.hiplc

Commonality Among Constraints

Vellum Constraints with Wind (POP Force applied) in Houdini

Constraints in Houdini define how a piece of geometry behave and how they move in the simulation when external forces are exerted upon them. Glue constraints describe how the pieces are bonded together and define how they behave when impacted by external forces. Vellum constraints define how the geometry will bend and stretch at the constraint points.

You start to see a commonality among all constraints in Houdini and how they are visually represented. Basic wireframe lines shown in the 3D viewport is the usual way of representing constraints in Houdini, whether it may be Vellum Constraints (see GIF animation on right) or Glue Constraints (see bottom screenshots).

These white wireframes are lines and they are primitives in Houdini. Constraints are actually geometry in Houdini that have special attribute data describing what type of constraint it is and certain features of the constraint points. These geometry primitives that the constraints are made up of, can be manipulated and created like how you create any other geometry in Houdini.

Destruction & Glue Constraints upon Impact in Houdini

Destruction & Spring Constraints upon Impact in Houdini

Glue Constraints

In destruction, there are many types of interesting constraints to use in the DOPNET, but for simplicity I demonstrate how to use the spring and glue constraints in the tutorial video (link is above). Glue constraints are very simple, they break upon impact or if the impact isn’t strong enough to break the glue constraints, then the fractures simply stay bonded together.

Spring Constraints

Spring constraints are very interesting to play with in Houdini, because they give you unexpected results. The spring constraints are pulling back each bond, like it’s trying to pull each pair of fractured geometry bonded by the spring constraint and trying to pull it back into place.