name	render-ldraw
description	Render a legolization LDraw model (.ldr/.mpd) to PNG images from front, iso, and top angles so it can be visually inspected. Use whenever asked to see, view, preview, screenshot, render, or visually check a generated model — or to confirm a placement/color/stability change looks right in the actual bricks rather than only in tests.

Render & visually inspect an LDraw model

legolization emits .ldr/.mpd files. Tests confirm geometry and physics, but they don't show what the model looks like. This skill renders a model to PNGs and then reads them back so you can judge shape fidelity, colors, gaps, floating or missing bricks, and obvious instability.

Files

render.py — renders a model to <prefix>.{front,iso,top}.png next to it.
preflight.sh — installs a headless renderer + LDraw parts library.

Workflow

Ensure a renderer exists (once per environment). If render.py reports renderer: NONE, run:
```
bash .claude/skills/render-ldraw/preflight.sh
```
On Ubuntu/Debian this installs LeoCAD, Xvfb, and the ldraw-parts library (/usr/share/ldraw). On macOS it points you at LDView.

Generate a model to inspect, e.g.:

uv run legolization data/examples/heart.vox -o heart.ldr

Render it:
```
python .claude/skills/render-ldraw/render.py heart.ldr
```
Useful flags: --views iso (single angle, faster), --size 1600x1200 (higher resolution), --prefix NAME, --ldraw-dir DIR (override the parts-library location). The script prints RENDERED: <path> for each image and exits 0 if at least one was written.
Read each RENDERED: PNG with the Read tool to view it, then describe what you see and compare it against the intended model — silhouette matches the source voxels, colors are right, no unexpected holes, no bricks floating free of the structure.

How it works

Auto-detects a renderer (ldview → leocad) and the LDraw parts library. A model file only references parts by id, so the renderer needs that library to draw anything beyond the most basic bricks (slopes and tiles render blank without it).
Success is decided by a non-empty PNG on disk, not the exit code: an unconfigured LDView exits 0 without writing a file, and LeoCAD under xvfb-run can exit non-zero after writing a valid one.
Re-rendering moves the previous images into previous/<UTC timestamp>/ so you can diff a change against the prior look.

Notes

Camera angles are (latitude, longitude) in degrees: front (0,0), iso (30,45), top (89,0). Add or change views by editing VIEWS in render.py.
To inspect the multi-step build sequence, render the .ldr as-is — the 0 STEP metas don't affect a full-model snapshot; open it in LDView or BrickLink Studio to step through interactively.
The generated *.png and previous/ directories are build artifacts; don't commit them.

Render & visually inspect an LDraw model

Files

render.py — renders a model to <prefix>.{front,iso,top}.png next to it.

preflight.sh — installs a headless renderer + LDraw parts library.

Workflow

Ensure a renderer exists (once per environment). If render.py reports renderer: NONE, run:

bash .claude/skills/render-ldraw/preflight.sh

On Ubuntu/Debian this installs LeoCAD, Xvfb, and the ldraw-parts library (/usr/share/ldraw). On macOS it points you at LDView.

Generate a model to inspect, e.g.:

uv run legolization data/examples/heart.vox -o heart.ldr

Render it:

python .claude/skills/render-ldraw/render.py heart.ldr

Useful flags: --views iso (single angle, faster), --size 1600x1200 (higher resolution), --prefix NAME, --ldraw-dir DIR (override the parts-library location). The script prints RENDERED: <path> for each image and exits 0 if at least one was written.

Read each RENDERED: PNG with the Read tool to view it, then describe what you see and compare it against the intended model — silhouette matches the source voxels, colors are right, no unexpected holes, no bricks floating free of the structure.

How it works

Auto-detects a renderer (ldview → leocad) and the LDraw parts library. A model file only references parts by id, so the renderer needs that library to draw anything beyond the most basic bricks (slopes and tiles render blank without it).

Success is decided by a non-empty PNG on disk, not the exit code: an unconfigured LDView exits 0 without writing a file, and LeoCAD under xvfb-run can exit non-zero after writing a valid one.

Re-rendering moves the previous images into previous/<UTC timestamp>/ so you can diff a change against the prior look.

Notes

Camera angles are (latitude, longitude) in degrees: front (0,0), iso (30,45), top (89,0). Add or change views by editing VIEWS in render.py.

To inspect the multi-step build sequence, render the .ldr as-is — the 0 STEP metas don't affect a full-model snapshot; open it in LDView or BrickLink Studio to step through interactively.

The generated *.png and previous/ directories are build artifacts; don't commit them.