gn-modifier-inputs

GN Modifier Inputs

A runnable example that attaches one Geometry Nodes tree to three cubes and writes a per-modifier Float Scale input through the version-appropriate API. The tree scales a 1 m cube by that value and lifts it onto the floor. Evaluated Z-extent must match the written scale (1 / 2 / 3). That is the closed form: if the write did not land, the three cubes collapse to the socket default and the extents are no longer distinct.

What it witnesses: Blender 5.2 removed ID-property assignment on NodesModifier. mod["Socket_1"] = 2.0 raises TypeError rather than silently no-opping. 4.5 LTS and 5.1 still require that dict form; mod.properties does not exist there (AttributeError). 5.2+ writes mod.properties.inputs.Socket_1.value. After the write, the depsgraph must be updated or evaluated_get still sees the previous scale.

Follows geometry-nodes-python.

Run

# Cheap correctness check (no render) — the CI check:
blender --background --python gn_modifier_inputs.py --

# Force one side of the split (must fail on the other series):
blender --background --python gn_modifier_inputs.py -- --api dict
blender --background --python gn_modifier_inputs.py -- --api rna

# Also render a still (EEVEE on a GPU host; use --engine cycles on GPU-less hosts):
blender --background --python gn_modifier_inputs.py -- --output stairs.png
blender --background --python gn_modifier_inputs.py -- --output stairs.png --engine cycles

It exits non-zero on failure (missing identifier, write/read raise, readback mismatch, evaluated Z-extent ≠ scale, or three extents not distinct). The blender-smoke workflow runs the check on Blender 5.2 LTS and 4.5 LTS (5.1 on the weekly cron).

Falsification

Probe	Binary	Result
--api dict	5.2.1 LTS	exit 5, TypeError: id properties not supported for this type
--api rna	4.5.11 LTS	exit 5, AttributeError: 'NodesModifier' object has no attribute 'properties'
--api auto	5.2.1, 5.1.2, 4.5.11	exit 0, extents 1.000 / 2.000 / 3.000