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The Pyro Source Instance SOP injects spawn points generated by Pyro Spawn Sources and creates instance points for them when they activate. These instance points can be fed to the Pyro Solver SOP to drive a simulation using packed sets.
In addition, this operator can register rule overrides that allow you to systematically adjust certain source rules with values of point attributes. As a
simple example, you can randomize an attribute and use it as a scale multiplier
for any rule that applies to the
temperature field; this will result in different sources being hotter or colder (possibly for the same packed source
set). You can achieve this by following these steps.
Randomize the scale of any rule that affects the
The registered Overrides are applied to all incoming spawn points. Assigning
the value of
1 to the Attribute will effectively leave the rule untouched
for that spawn point (the value is used as a multiplier). This way you can exclude certain spawn points from an override. Alternatively, it’s possible to use two different Pyro Source Instance nodes for different spawn points, each with their own overrides. The generated instance points from these two nodes can be merged and passed to the solver together.
Attributes on instance points are read by the Pyro Solver to determine which source set to apply, where to apply it, and how. These relevant point attributes are listed below.
Name of the packed source set that should be applied. This is copied from the spawn point.
Location of the instance in world space. This is copied from the spawn point.
Orientation of the instance in world space. This is copied form the spawn point.
The local pivot point for this instance. This is copied from the spawn point.
Offset into the relevant packed source set’s sequence. A value of
indicates that the very first frame of the packed source set should be
used. This is calculated using the current frame and the spawn point’s
This dictionary array attribute stores the sourcing rules that govern how the volumes of the packed source set will be merged into the pyro simulation. Each entry in the array stores an individual rule, containing all the data that comes with a single entry under the Source Volumes section of the Pyro Solver SOP. The instance’s rules are copied from the corresponding packed source set and modified to incorporate any relevant Overrides registered on this Pyro Source Instance node.
Spawn points created by the Pyro Spawn Sources node.
Packed Source Sets
Library of packed source sets (each created using the Pyro Source Pack SOP). The current frame offset for each input spawn point is checked against its packed source set’s frame range; if in range, an instance point is created from it. Additionally, source rules are transferred from the packed sets to the instance points, with Overrides applied.
Reference frame for the library of packed source sets. All source sets in the library are timeshifted to start on this frame for consistency. The value of this parameter should match the Reference Frame on Pyro Source Pack nodes that were used to generate packed source sets in the library (second input).
When turned on, you see a guide geometry in the viewport to visualize the actual sources for each instance point.
You can use point attributes on the spawn points to adjust certain properties of source rules (that come from the packed source set). To this end, the attribute can be registered as an override using this multiparm. The value of each point Attribute is applied multiplicatively to the selected Property, for any rule that applies to Target Field.
Identifies which rules should be adjusted: any rule that applies to this Target Field will be adjusted using values of the Attribute.
Specifies which property of the rule to override. The value of this property for the relevant rule is scaled by the value of each spawn point’s Attribute.
Name of the point attribute on the spawn points. The value of this attribute is applied as a multiplier to the selected Property for any rule that applies to Target Field.
You can also randomize a specific attribute of the Target Field. Enter the attribute’s name and click the button on the right side of this parameter to randomize the value of the Attribute for each spawn point. This will create or select a corresponding attribute adjust node to give you greater control over the attribute’s values.