Houdini 20.0 Dynamics

Visualizing dynamics

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  • Remember that the slice is just that: a 2D slice through a 3D volume, and so sometimes it can be deceiving. For example, at a particular moment a temperature slice might look like there’s no temperature in your container, when in fact there just happens to be no temperature in that slice.

    You might try moving the slice or switching to a smoke visualization occasionally.

  • To eyeball what temperatures are present where in your effect, turn on visualization of the temperature field (Smoke object > Guides tab > Temperature tab). Then use the Guide range parameters to adjust the minimum and maximum temperatures visualized (the ladder control is useful here).

    For example, to see the correlation between temperature and shredding, turn on the temperature and shredding visualizations, and on the smoke object’s temperature visualization tab, set the Guide range to the range of temperatures where shredding occurs (controlled by Pyro solver > Shape tab > Shredding tab, Temperature threshold and Threshold width).


  • To hide very low velocities so you can focus on more meaningful streamers, increase the Streamer Minimum Speed.

  • You can eyeball a rough estimate of the maximum speed in a sim by decreasing the maximum Visualization Range value until just before all red (in the Infra-Red color mode) disappears from the streamers. The maximum value is then roughly the maximum velocity in the system.

Show an object’s collision representation

The dynamics engine uses a simplified version of an object’s geometry to calculate collisions.

To show this geometry in the viewer, show the object’s parameters and click the Collisions tab, then the Volume sub-tab, then turn on Show collision guide geometry.

Cloth and wire visualization

The Cloth Object and Wire Object have Visualization tabs that let you show the effects of forces on the object as colored lines.

The most important forces for cloth are external forces, collision forces, impacts, stretch energy, and sometimes stretch force and biphasic force.

Fluid visualizations

  1. Select the Smoke (density) or Fluid (sign distance) box you want to visualize. If you're not already in the dynamics network, choose the Select tool and Dynamics selection mode, then click the box in the viewer.

  2. In the parameter editor, click the Guides tab at the bottom.

The Guides tab contains many sub-tabs with controls for visualizing different aspects of the field. For example, you can use the controls on the Velocity sub-tab to view the velocity of the contained gas/fluid at each point using lines, or through a plane using streamers.

Using visualization geometry

You can import visualization geometry into a geometry network just as you can import the actual surface or volume of an object. See the section on importing and exporting simulation data.


Learning dynamics

Colliding objects

Simulation types

Next steps