L-System

The pipeline has a CPU half and a GPU half. On the CPU, the Axiom string is rewritten by the Rules for Iterations passes (clamped 0–12, bounded at 1 000 000 symbols — overflow sets the Truncated output instead of failing silently). Rule syntax is one rule per line with # comments; both -> and = are accepted, and stochastic rules use weight-tagged alternatives: X -> (0.6) F[+X] | (0.4) F[-X]. Stochastic choices use a seeded RNG, so the same Seed always replays the same figure.

The expanded symbol string is walked by a 3D turtle (ABOP-standard alphabet):

Three turtle-level parameters add 3D character to any grammar without editing its rules: Branch Roll rolls the frame at every [ (137.5° gives golden-angle phyllotaxis — planar plants become 3D bushes), Twist rolls after every drawn segment (flat curves become spatial ribbons), and Jitter 3D applies seeded random pitch/roll per branch. The figure is normalized root-anchored: the start point sits at the origin and the longest bounding-box side is scaled to 1.6 Grafit units. Segment count is capped at 250 000.

Geometry is rebuilt only when a grammar/turtle input changes (hash-cached); everything else — growth reveal, wind, pulse, dash flow, symmetry copies, perspective — is computed per frame in a single instanced GPU draw call from baked per-segment attributes, at zero CPU cost. A planarized twin of the figure is baked alongside the 3D form, and Depth 3D morphs between them entirely on the GPU (0 = flat, 1 = full 3D).

Growth (0–1) reveals the figure. Three modes:

Grow Variability (Path mode) gives each branch a seeded random growth speed that compounds down the hierarchy, so branches race organically while staying connected.

Color Mode — Solid (the Color port), Gradient (a connected Gradient node sampled by Gradient By: Depth, Path, Branch, Angle, Length, or Height, offset by ' color indices), or Metallic (cylindrical shading with anisotropic specular controlled by Shine). Dash cuts strokes into a dash pattern (Dash Ratio = filled fraction) and Flow animates it along the path; Flow without Dash becomes a traveling brightness wave. Wind is a position-only displacement field (so parent and child segments can never tear apart at joints), Pulse breathes the stroke width, Shimmer adds per-segment brightness sparkle. All animation defaults to 0 — nothing moves by itself; the Time port (< 0 = internal clock) lets you drive or scrub the clock externally.

Copies (1–24) plus Copy Axis build symmetry: Screen (mandala in the screen plane), Carousel (copies fanned around the vertical axis), Wheel (around the horizontal axis). Mirror doubles everything with an X-flip, and Copy Rotate adds per-copy rotation. Camera Distance applies per-endpoint perspective (0 = orthographic), and Depth Fade darkens far elements toward black over Fade Range.

Beyond Image / Width / Height (figure bounding box × Scale), the node emits its skeleton as structures: Points (all segment endpoints), Tips (terminal endpoints), Live Tips (the tips of the currently grown tree — in Path mode slot-stable, one point per final tip, so index-paired consumers never flicker), Structure (an ordered bundle { root, tips, forks, liveTips } — open it with Get by Name), Count (segment count), and Truncated. All point outputs pass through the exact same transform chain as the rendered figure (including wind and perspective), capped at 10 000 points per category. Output is premultiplied alpha, and Enable = false clears the texture.

Grammar

Transform & 3D

Stroke, Symmetry & Growth

Animation, Color & Glow

Presets

The inspector's preset dropdown writes into the ports (Axiom, Rules, Angle, Iterations, Length Falloff, Taper, Rotation, Branch Roll, Twist) — an editable starting point, not a mode. The 27 presets:

Botanical: Fractal Plant, Fern, Bushy Tree, Weeping Willow, Wild Grass, Grass Clump, Vine, Root System, Seaweed, Conifer.

Geometric / fractal: Dragon Curve, Koch Snowflake, Koch Island, Sierpinski, Hilbert Curve, Gosper Curve, Levy C Curve, Pentaflake, Crystal, Cross Fractal.

Artistic / organic: Lightning, Coral, Mandala, Snow Crystal, Circuit Board, Feather, 3D Tree.

• Growing plant: Fractal Plant preset, Time → LFO (sawtooth) → Growth in Path mode with Grow Variability 0.5 — a tree that grows connected from the root, branches racing organically
• Audio-reactive fractal: Audio FFT → Remap → Wind and Pulse on a Fern, with Glow Power for a concert visual
• Mandala engine: any preset + Copies 8–12 on Copy Axis Screen, Rotation driven by Time — instant kaleidoscopic symmetry; switch to Carousel and add Rotate Y for a 3D crown
• Plexus hybrid: L-System Live Tips → Plexus Points — a constellation web that rides the advancing growth front (slot-stable in Path mode, so it never flickers)
• Particle emitter skeleton: Structure → Get by Name (forks or tips) → a particle system's emitter points, so sparks pour from branch junctions
• Neon signage: Dragon Curve preset, Color Mode Metallic with high Shine, Dash 0.05 + Flow 2 for marching neon dashes, plus Glow

• The Image output needs a Canvas node to be visible; Width/Height report the figure's bounding box (× Scale), so a Canvas can wrap it exactly
• Iterations is exponential — going from 5 to 7 can multiply segments by 16×. Watch the Truncated output (and the inspector warning) and back off rather than pushing the 250 000-segment cap
• Path growth mode guarantees a connected tree at every Growth value; By Depth and Per Branch are stylistic fronts that may reveal detached pieces mid-animation
• Wind is deliberately visual-only for point outputs on static patches; cable the Time port if downstream point consumers must sync exactly with the swaying image
• Branch Roll 137.5 is the single most effective knob: it turns any flat preset into a believable 3D bush — then spin it with Rotate Y
• A preset is a starting point: edit the Rules text afterwards and the dropdown flips to Custom without losing your changes
• Glow, like all generator bloom, is a post-process; AA is global (the app-wide AA multiplier), with no per-node quality settings