mat_fern

# fl_frond The foliage shader of *First Light: Goura* — fern fronds, palm blades, sapling leaves and the roost tree's crown. Thin geometry that has to read twice over: as a black silhouette against the last of the night, and as a lit, translucent leaf when the first gold arrives low from the side. A `surface()` shader with a `vertex_clip()` hook. Three things it does that the ground shader (`fl_surface`) does not: **Sway.** `vertex_clip` displaces each vertex by an amount the MESH declares in its vertex alpha — 1 at a frond's tip, 0 where it is rooted — so a frond pivots from its crown instead of sliding whole. The phase is a function of world position, so a stir travels across the lane rather than every copy of the same mesh nodding together. The displacement takes the vertex's own `time`, so the previous-frame evaluation places the leaf where it was a frame ago and the motion vector carries the movement. `sway` is the amplitude in metres at a free tip; set it to 0 for geometry that should stand still. **Translucency.** `subsurface_color`, `subsurface_amount`, `subsurface_radius` and `thickness` give the lobe that makes a backlit leaf glow instead of going black — the reason a low dawn sun through a fern bed is worth drawing at all. **A blade read off the UVs.** The frond meshes carry `uv.x` ACROSS the blade (0 at the spine, 1 at the edge) and `uv.y` ALONG it. `rib_width` / `rib_darkness` darken the midrib, `edge_color` / `edge_amount` pale the edge, `base_tint` ages the end nearest the crown, and `bow` bends the shading normal across the blade so a highlight travels along a frond rather than flashing the whole leaf at once. None of that is in the geometry. ## Vertex colours - `rgb` — the leaf's own tone, multiplied over `base_color`. - `a` — sway freedom, and (through `cavity`) ambient occlusion, so a fern's crown sits in its own shadow. ## Properties `properties.yaml` carries the full set. `double_sided` defaults on: this geometry is meant to be drawn by a material with `cull: none`.