lum_glyph

Unlit HDR glow shader for the lumen opener's lettering (preseed/parts/p1_lumen). Renders mix(color, hot_color, heat) * intensity with a view-rim lift and a slow vertical shimmer, so a driven intensity takes a glyph mesh from ember-dark to bloom-hot without touching the lit PBR layer in front of it. Material instances: lum_glyph_mat (the title's driven back-glow) and lum_glyph_sub_mat (the subtitle's static soft glow).