03_plot.md

Step 3 — Polar intensity diagram

eulumdat-plot generates polar intensity diagrams (cd/klm) in Lumtopic style: a banner showing the luminaire type and unit, solid lines for C0/C180, and dashed lines for C90/C270. Output formats are SVG (vector) and PNG (raster).

From this step onward we use sample_isym4.ldt — the symmetrised file is the standard input for visualisation and analysis tools.

---

from pathlib import Path
from eulumdat_plot import plot_ldt_svg
from eulumdat_plot.export import svg_to_png

Path("output").mkdir(exist_ok=True)

# SVG output (vector, opens in any browser)
svg_str = plot_ldt_svg("samples/sample_isym4.ldt")
svg_path = Path("output/plot.svg")
svg_path.write_text(svg_str, encoding="utf-8")
print("SVG written: output/plot.svg")

# PNG output (raster, for Word or presentations)
svg_to_png(svg_path, "output/plot.png")
print("PNG written: output/plot.png")

print("Open output/plot.svg in your browser to see the polar intensity diagram.")

Expected output:

SVG written: output/plot.svg
PNG written: output/plot.png
Open output/plot.svg in your browser to see the polar intensity diagram.

Open output/plot.svg in your browser — this is your first visual result. The solid lines represent the C0/C180 planes (longitudinal), the dashed lines represent C90/C270 (transversal). For a linear luminaire like this sample, the two profiles are very different, which is expected.

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Script: scripts/step_03_plot.py

See also: eulumdat-py includes a lightweight matplotlib-based polar diagram example if you prefer a quick plot without additional dependencies — 02_polar_diagram.md.

Next step → Step 4 — Luminance table and polar diagram