Live rendered thumbnail previews above every node in the Blender Shader Editor.
Node Peek renders a small thumbnail of each node's output and draws it above the node, updating as you work — so you can see what every node in your shader is doing without plugging it into the output.
Previews are computed by a separate background Blender process, so your UI stays responsive and nothing is ever written into your .blend file.
An independent, clean-room implementation inspired by the idea behind the commercial "Node Preview" add-on. It shares none of that product's code.
Requires Blender 4.2+. Works on macOS, Linux, and Windows.
- Download
node_peek.zip(or zip thenode_peek/folder yourself). - Blender → Edit → Preferences → Add-ons → Install from Disk… → pick the zip.
- Enable it. Open a Shader Editor and select an object with a node material.
- Previews appear above nodes automatically (when Previews Visible By Default is on).
- Sidebar (N) → Node Peek tab for controls (Refresh, Clear, resolution).
- Ctrl+Shift+P — toggle previews on the selected nodes (used when Previews Visible By Default is off).
- Enter a node group (Tab) and its interior nodes get previews too.
| Preference | Meaning |
|---|---|
| Previews Visible By Default | Show previews on all nodes, or only manually-enabled ones |
| Thumbnail Resolution | 32–512 px render size per node |
| Update Delay | Debounce after the last edit before re-rendering |
| Render Engine | Cycles (reliable) or EEVEE (experimental — often black in background) |
- A single background Blender (
blender --background, runningworker.py) starts once and stays alive — no per-edit startup cost. Requests are sent over the worker's stdin: it blocks on read (zero idle CPU) and exits on EOF if Blender closes the pipe, on any platform. - On a change, the add-on writes just the active material (
libraries.write, not the whole .blend) and sends a request. A cheap tree fingerprint suppresses requests when nothing preview-relevant changed (e.g. selecting a node). - The worker hashes each node's content — everything upstream, node-group internals, and image file mtimes. Only nodes whose hash isn't already cached are re-rendered; the rest are reused instantly. The cache survives undo/redo and reverted tweaks.
- Results are streamed: the node you're editing renders first and appears immediately, without waiting for the whole job.
- Texture/color/vector nodes render as a flat map (orthographic plane + emission, 1 sample — noise-free). Real shader nodes render as a shaded sphere (adaptive sampling + denoise).
- Image texture datablocks are cached across jobs; renders land in the cache via atomic rename (a killed worker can't corrupt it); GPU textures are content-addressed and shared between nodes with identical output.
| Situation | Cost |
|---|---|
| First open of a material | Renders every node once (fills the cache) |
| Tweak one node's value | Re-renders that node + downstream only, edited node first |
| Undo / revert a value | Instant — served from cache |
| Switch object / material | Cached nodes instant, new ones rendered |
| Select / move a node | No render (fingerprint unchanged) |
| Idle | Worker blocked on stdin — zero wake-ups |
Entering a group shows per-node previews inside it, rendered for the specific instance you navigated through (its inputs are baked in) by temporarily routing each node's output through the group interface in the throwaway worker copy — your file is never touched. Arbitrary nesting depth is supported.
A group used by several instances resolves to one representative instance when you step in (the first found); with a single instance it is exact.
- Multiple Shader Editors open at different group depths at once: only the one showing the active material (first found) has its interior rendered.
- Painting into a packed image doesn't invalidate the cache (no file mtime) — use Refresh Previews.
- Previews render the Surface shader only: a material driven by the Material Output Displacement input shows its bump/normal detail but not the displaced silhouette.
- Collapsed (hidden) nodes are skipped.
- View transform is forced to Standard, so previews won't match an AgX/Filmic look.
- World and Geometry Nodes trees are not handled (Shader Editor only).
The background worker logs to worker.log (its path is printed to Blender's
console — Window → Toggle System Console — on the first render). If previews
don't appear, that log shows whether renders are failing and why. Refresh
Previews re-renders everything ignoring the cache.
Built by mlstr0m — Résidence Principale.
GPL-3.0-or-later. See LICENSE. (Blender add-ons must be GPL-compatible because they link against Blender's Python API.)
Issues and pull requests welcome. The whole add-on is two files: __init__.py
(the Blender-side UI, drawing, and IPC) and worker.py (the background renderer).