Houdini 21.0 Nodes Copernicus nodes

Reaction-Diffusion Block Begin Copernicus node

Start of a Reaction-Diffusion simulation block.

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Since 21.0

This node is the beginning of a Reaction-Diffusion simulation block. Reaction-Diffusion simulations are complex 2D simulations of chemicals reacting and diffusing.

Note

Operations that're independent of previous frames should occur before the Reaction-Diffusion Block Begin so that they only get cooked once. Post-processing operations that aren’t required to feedback should occur after the Reaction-Diffusion Block End.

Use the passthrough input to bring additional inputs inside the block. Use the feedback input to add additional values that must be updated every frame.

See Reaction-Diffusion solver for information about how to use this node.

Parameters

Signature

The signature mode to evaluate the activation input as. This also controls how the reaction initiates using the activation pattern.

Activation (Mono)

Use a mono input pattern to initiate the reaction with. In this mode, it’s best to provide high contrast noise patterns to help the reaction start.

Chemical (UV)

Use a UV input, which causes the reaction to continue using the raw chemical values. Use this to stack multiple Reaction-Diffusion blocks.

See Signatures for more information.

Block Path

The path to the Reaction-Diffusion Block End COP that’s the final and closing node of this block. The Reaction-Diffusion Block End node must be at the same network level as this Reaction-Diffusion Block Begin node.

Continuous Activation

Makes the simulation evaluate the activation pattern as if it were a constant source. When off, the simulation evaluates the activation pattern on only the first frame.

Inputs

activation

The activation pattern with which the reaction initiates.

Note

Unless Continuous Activation is on, this is read on only the initial frame.

alpha

An input to control the Alpha coefficient in the reaction. This is read on only the initial frame.

beta

An input to control the Beta coefficient in the reaction. This is read on only the initial frame.

gamma

An input to control the Gamma coefficient in the reaction. This is read on only the initial frame.

scale

An input to control the reaction scale. This is read on only the initial frame.

coefficient

An input to control the Diffusion Coefficients in the reaction. This is read on only the initial frame.

boundary

An input to control the boundary of the reaction. This causes the reaction to grow organically into the SDF shape. This is read on only the initial frame.

feedback

A cable with wires that are fedback to the next iteration of the solve. The input’s cable structure must exactly match the Reaction-Diffusion Block End’s input. This is read on only the initial frame.

passthrough

An optional cable with layers and VDBs that should be computed outside of the simulation. These are read each frame, so they can’t depend on the results of the simulation, but you can use them to inject animated sources.

Outputs

chemical

The raw chemical reaction.

feedback

A cable of the extra data that’s been fedback to this frame.

passthrough

A cable that passes through the input, updating every frame from the input.

See also

Copernicus nodes