Houdini 12 Shelf tools

Creates a force that pushes away from the selected object. This lets you expand (blow up) a fluid system at a specific time in a specific shape, which is useful for explosions.

(Technically, the expansive force is a divergence field.)

See fluid sourcing for information on how the tool transforms the input object into a source for the effect.

Using Expand from Objects

To...Do this
Create a fluid container

See Smoke Container, Flamefront Container, and Liquid Container.

Fill a fluid container

See Source from Surface, Source from Points, and Source from Volume.

Create an expansion force

  1. Select the object you want to turn into an expansion field.

  2. On the Populate containers tab, click the Expand from Objects tool.

  3. Select the fluid container you want to expand in and press Enter.

Control the amount of expansion

In the DOP network, find the Source Volume node importing the divergence field (named source_divergence_from_object).

Use the Scale source volume parameter to control the amount of expansion. You can keyframe this value to delay and/or limit the expansion time, pulse the expansion, etc.

Sometimes very high values may be necessary (100+) to have visible effects.

Tips

  • The shelf tool adds a Fluid Source surface node to the object to convert its geometry into an appropriate volume, then imports the volume into the DOP network using a Source Volume node.

  • Most “populate containers” defaults are configured for a sphere with a radius of 1 unit. For much smaller or larger volumes, you may need to change settings on the Fluid Source surface node created by the shelf tool. The Sample Radius, Edge Location and Feather Length parameters give extensive control over how everything is sampled into a volume.