# Doom 3 – Volumetric Glow (GAT #33)

Source: https://simonschreibt.de/gat/doom-3-volumetric-glow/
Author: Simon Schreibt. Captured 2026-10-16.

## Terminology (Simon’s usage)
- Glare: too bright, loses sharpness; gone when source not seen directly.
- Haze: lit fog; visible even without seeing source.
- Lens flare: camera lens imperfections.
- Doom 3 light aura behaves like mild haze but disappears without direct sight (glare-like). Materials call them “flare”.

## Alternatives Simon listed
1. Fullscreen bloom blur — memory, automatic scale with visible area.
2. Hand-placed glow planes — stays without LOS (haze); artist cost.
3. Big camera-facing sprite — poor for rectangular Doom 3 light areas.

## Observed technique
- Artist places a polygon/quad + predefined material (e.g. desk lamp).
- Runtime folds/unfolds a (likely vertex-colored) mesh for volumetric look—wireframe shows expanded silhouette.
- Drawn only when facing the light; fades with angle (suspected vertex color).
- Artifacts: aura “moves” when walking near; cuts wall with rotating feel (planes not hand-placed fixed).

## Community theory
- Recycle silhouette/extrusion ideas related to Doom 3 shadow volumes: screen-space expand edges, extra corner verts for rounding; convex light surfaces.
- Reimplementations: Yzer, Hollowdilnik, WebGL (michaeldll), Unity DoomGlow variants.