Simulate
The Simulate node is the engine of Natsura. It takes the abstract graph recipe built from Grow, Split, Repeat, and the rest of the node set, then executes it to generate geometry: traversing the graph, resolving all mappings, effectors, and conditions, and producing the final skeleton and decoration geometry. It runs a feedback loop where, in each step, active tips grow, conditions are checked, attributes are updated, and new tips are spawned.
Inputs
| Input | Description |
|---|---|
| Input 0: Graph | The Natsura graph to simulate. |
| Input 1: Parms (optional) | Global parameter dictionary. |
| Input 2: Points (optional) | Source points for "Grow from Points" mode. |
Outputs
| Output | Description |
|---|---|
| Output: Geometry | The generated skeleton and / or decoration geometry. |
Intrinsics
| Attribute | Description |
|---|---|
id | Unique identifier per internode. |
parent_id | Parent internode. |
generation | Recursive depth from the root. |
u | Normalised progress along the growth section. |
age | Time / step counter. |
width | Branch thickness. |
radius | Branch radius derived from width. |
orient | Orientation quaternion on decorations. |
scale | Scale factor on decorations. |
variant | Variant index on decorations. |
Parameters
Globals
| Parameter | Description |
|---|---|
| Generation | By default, the current frame number is used; the frame number can be set using the playbar at the bottom of the interface. |
| Max Steps | Safety limit for the simulation loop. Prevents runaway growth. |
| Seed | Global random seed for the simulation. |
Output
| Parameter | Description |
|---|---|
| Output Skeleton | Generates the line graph representing the branch structure. |
| Output Decorations | Generates instanced geometry (leaves, flowers, etc.) attached via decoration sockets. |
| Point Attributes | Specify which attributes (N, width, Cd, and so on) to retain for points. |
| Primitive Attributes | Specify which attributes to retain for primitives. |
| Keep Dead Stuff | Enable to preserve parts of the geometry marked as inactive. |
Modes / States
Three display modes control what the node shows in the viewport:
- Skeleton. The line graph only; fastest for iteration.
- Preview. Lightweight shading.
- Output. Final decorated geometry; the most expensive mode.
Notes
- Reduce Max Steps or use simpler graphs when iterating. Full decoration output is the most expensive mode.
- Simulate is the mandatory final step; no geometry is produced without it.
- Feed a scatter into Input 2 to grow many instances from different root positions. See Variation.
See also: Simulation concept · Variation · Grow · Seed Points
Simplify Tree Rig and Skin
Reduces joint count and skin complexity on a rigged Natsura tree before export. The standard pre-export step for Unreal Nanite Skeletal Assembly.
Split
Creates explicit parallel branches in the growth graph. Distinct from innate forking, Split allows you to fork the topology into separate, distinct logical paths.