HeightfieldPatchOptions

interface HeightfieldPatchOptions

import type { HeightfieldPatchOptions } from '@driftengine/terrain';

In depth

A patch is the unit of detail, and the seam between two of them is the whole problem. A heightfield drawn at one resolution is either too coarse underfoot or too fine at the horizon, so it is drawn in squares and the distant squares skip samples. Where a square that skips none meets one that skips every other, the fine edge has vertices the coarse edge does not — and those vertices sit on the field while the coarse edge cuts the chord beneath them. The gap between the two is a crack, and a crack in terrain is a hole through to the sky.

Matched rather than hidden. The usual remedy is a skirt: a vertical curtain dropped from every patch edge, which fills the hole with something the wrong colour and lit the wrong way, and costs geometry along every boundary in the world for ever. What this does instead is move the fine edge's odd vertices onto the coarse edge's own straight segment, so the two edges are the same polyline and there is nothing to fill. It costs one interpolation per boundary vertex, at build time, and no geometry at all.

The cost of matching, stated because it is real: along a matched edge the drawn surface is the coarse chord rather than the field, so Terrain.heightAt and the picture differ there by up to the sag of one coarse cell. That is the same error the coarse patch itself carries over its whole area, arriving one cell early — which is why it is the right trade and why it is written down rather than left to be discovered.

Properties