coveredAbove

function coveredAbove(surface: GroundSurface, x: number, z: number, fromY: number, toY: number, scratch: SurfaceHit): boolean

import { coveredAbove } from '@driftengine/physics';

Parameters

In depth

The general question, of which "should rain fall here" is one caller. A surface answers three things and only two of them had names: where the ground is, whether a floor is in the way, and — the one this is — whether the sky is visible from a point. That third question is asked by more than weather, and it is asked constantly: rain and snow that stop under a canopy, a puddle that only forms where the sky reaches, a shaft of sun that should not appear indoors, an agent deciding whether it is worth taking shelter, a plant that grows toward light. Every one of those is sampleBand over the column above you, and every consumer that wants one would otherwise discover that for themselves.

A hole is a hole, for free. This is the property worth stating, because it is what usually separates a convincing effect from a stamped-on one: the answer comes from whether the surface has a face in that column, so a roof with a gap in it, a RibbonSurface with a stretch of holes, a run of pads with air between them, or a bounded heightfield past its own edge all let the sky through in exactly the places they look like they should. Nothing describes the opening twice and nothing can disagree with the geometry it was cut from.

toY is where the caller stops caring — a cloud base, the top of a level. Half-open like sampleBand, so a face exactly at toY is above the question rather than in it.