Notch Reference Manual

Reaction-Diffusion

Method

Performs reaction-diffusion simulation, using a procedural input to restict the placement of seeds and another procedural input to restrict growth.

This node simulates the Gray-Scott reaction-diffusion process, which can be thought of as a kind of fluid simulation with an extra step that creates organic-like patterns which grow out from seed points. Seed points are created by random spread, and if a seed restrictor is used then seeds outside of the restrictor volume are rejected. The growth is limited by the growth restrictor volume. There are options to invert these volumes.

More information on the general topic of reaction-diffusion simulation can be found here

Example
Example Nodegraph

Attributes

Name Description
Distance Offset Offsets the distance field values, causing the generated distance field to expand of contract.
Filled Mode Thickness of the Shell wall, when Filled Mode is set to Shell.
Shell Thickness Thickness of the Shell wall, when Filled Mode is set to Shell.
Simulation Grid Width/Height/Depth The voxel resolution of the simulation grid used for performing the reaction-diffusion simulation
Material Colour Modify the colour for the procedural material.
Initialisation Seed The randomisation of the seed points can be changed by changing this seed value
Smoothen When enabled, the surface extracted from the simulation is smoothened internally
Growth Pattern Changes the type of growth that occurs. At 0.0 the growth will be more like a web, and at 1.0 the growth will be more like separated blobs.
Growth Rate Controls the speed at which the growth progresses.
Invert Growth Restriction Inverts the in/out sense of the restriction volume
Seed Density Increase this property to make the seed points appear more densely packed together. Decrease it to spread them out more.
CSG Mode These options change how a this node combines with the rest of the procedural system. To find out more, see CSG Operation.
  • Replace, Replaces the previous procedural system.
  • Union, Adds the new procedural to the old procedural system.
  • Intersection, Interesects the new procedural with the old procedural.
  • Subtract, Subtracts the new procedural from the previous procedural system.
  • Blend, Blends between both procedurals – driven by the CSG Blend Weight.
  • Union Blend, A combination of Union and Blend – driven by the CSG Blend Weight.
  • Smooth Union, The new procedural is added to the old, and smoothing is applied to the outcome. Driven by the CSG Blend Weight.
  • Smooth Subtract, The new procedural is subtracted from the old, and smoothing is applied to the outcome. Driven by the CSG Blend Weight.
  • Offset, Adds one procedural ontop of the other another.
  • Custom Code, allows you to enter your own expression code.
CSG Blend Weight How much the new procedural blends with the old procedurals, depending on the CSG Blend Mode.
Affect Colour Affect the colour of the generated procedural system. only functions with “Generate Colours” enabled in some Procedural Render nodes.
Always Enabled (No Time Bars) When enabled, this node will run regardless of time bar enable/disable. Due to how Notch handles shader generation with procedurals, with this enabled the node runs more efficiently.
Custom CSG Code Type your Custom code here, using the HLSL language. Read more on Editable Code.

Inputs

Name Description Typical Node Input
Colour Ramp Specifies a range of colours the generator can use. Colour Ramp
Transform Modifier Links all transform properties to the input node. Null
Target Node Always faces the x-axis towards the inputs anchor point. Null
Local Transform Override Override the transformation values of the node, relative to its parent. Null

Outputs

Can be connected to any node which requires an image input.