cm_rain

# rain_streak Night rain for Smog: thin, cool grey-silver streaks falling at ~9 m/s with a slight wind slant toward +X, drawn additively so they only ever add light. Each drop is lit by the ambient, the moon (glinting when the moon is behind the rain) and every gas lamp near it (much brighter when the lamp stands behind the drop), so rain reads as sparkle around the lamps and fades into the smog with distance. Drawn on `art.fx.rain_drops` (one tiny card per drop, its seed in the vertex colour, its corner in the uv). `vertex_clip` builds a lattice of drops falling through a `volume_size` box centred on the camera that draws them, so one static entity rains around the player wherever they go. Wrap counts come from `uniforms.time` and positions from the evaluation's own time, so motion vectors carry the real fall speed. Point lights are read in the fragment stage (they are not bound to the vertex stage). Knobs: `density`, `fall_speed`, `wind`, `opacity`, `tint`, `streak_length`, `streak_width`, `pixel_width`, `lamp_gain`, `lamp_forward`, `moon_gain`, `near_fade`, `far_fade`, `volume_size`, `volume_lift`. Material: `art.fx.rain`.