Houdini 16.5 Pyro

Clustering smoke and pyro simulations

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Overview

Clustering partitions a large or sparsely-distributed smoke or pyro simulation into multiple (possibly overlapping) fluid boxes instead of one giant box.

Using multiple small boxes has several advantages:

  • Can be distributed to multiple processes and/or machines on a farm.

  • Solves faster since they computer doesn’t have to deal with the empty spaces between the important parts of the overall simulation.

  • The small boxes can be much higher resolution, or multiple resolutions, whereas a giant box usually must have a lower resolution because of memory limitations.

The multiple containers created by these tools are separate simulation objects with no interaction between each other. For example, density cannot move out of one container into an adjacent one. This is usually not a problem smoke and fire simulations

Creating a clustered smoke/pyro simulation from point sources

  1. Select the object containing the points you want to emit from.

    The smoke and pyro clustering tools only work with point sources. (This is because they use point clustering to partition the source.) If you select surfaces or volumes instead of pure points, the tool will first add a Scatter node to scatter points across/through the surfaces/volumes.

  2. On the Pyro FX shelf tab, click Smoke Cluster or Pyro Cluster.

    • Inside the object’s geometry network, the tool creates a Cluster Points surface node to partition the points. The clustering branches off into nodes operating on the "instance points" (the points that will emit smoke/fire) and "cluster points" (the points on which the containers will be centered).

    • On the "instance point" branch it creates a Fluid Source node to turn the points into fluid sources.

    • In the DOP network, the tool creates a regular pyro node setup. On the Smoke object, it turns on Create objects from points (on the Instancing tab) and imports the cluster points from the geometry network.

  3. To change the number of containers, in the geometry network select the Cluster Points node and change the Clusters parameter.

  4. Sourcing from points gives very thin smoke. The following controls will let you increase the source (in descending order of usefulness):

    • In the geometry network, on the Fluid Source node, in the Scalar volumes ▸ Stamp points sub-tab, increase the Sample distance. This is the radius around each point which will be added to the source field.

    • In the dynamics network, on the Source Volume node, you can increase the Scale source volume parameter to increase the output of the source.

    • Increase the number of scattered points before clustering.

Clustering animated point sources

It is possible to use clustering with an animated number of points, but it requires a couple of tricks to get the cluster boxes to appear as the points are created.

Load $HFS/help/examples/nodes/sop/clusterpoints/AnimatedSourcePoints.hda for an example of how to set this up.

See also

Pyro

Getting Started

Next Steps

Tutorials