webeditor3d/tests/geometry/terrain-brush.test.ts

import { describe, expect, it } from "vitest";

import { createDefaultTerrainBrushSettings } from "../../src/core/terrain-brush";
import { createTerrain } from "../../src/document/terrains";
import {
  applyTerrainBrushStamp,
  getTerrainBrushWeight,
  sampleTerrainHeightAtWorldPosition
} from "../../src/geometry/terrain-brush";

describe("terrain brush geometry", () => {
  it("samples terrain height across the regular XZ grid", () => {
    const terrain = createTerrain({
      id: "terrain-sample-height",
      position: { x: 0, y: 0, z: 0 },
      sampleCountX: 2,
      sampleCountZ: 2,
      cellSize: 2,
      heights: [0, 2, 4, 6]
    });

    expect(sampleTerrainHeightAtWorldPosition(terrain, 1, 1)).toBe(3);
  });

  it("raises and lowers height samples with radial falloff", () => {
    const terrain = createTerrain({
      id: "terrain-sculpt",
      position: { x: 0, y: 0, z: 0 },
      sampleCountX: 3,
      sampleCountZ: 3,
      cellSize: 1,
      heights: new Array(9).fill(0)
    });
    const settings = {
      ...createDefaultTerrainBrushSettings(),
      radius: 1.2,
      strength: 0.5,
      falloff: 0.5
    };
    const raisedTerrain = applyTerrainBrushStamp({
      terrain,
      center: { x: 1, z: 1 },
      settings,
      tool: "raise"
    });
    const loweredTerrain = applyTerrainBrushStamp({
      terrain: raisedTerrain,
      center: { x: 1, z: 1 },
      settings,
      tool: "lower"
    });

    expect(raisedTerrain.heights[4]).toBeCloseTo(0.5);
    expect(raisedTerrain.heights[0]).toBe(0);
    expect(loweredTerrain.heights[4]).toBeCloseTo(0);
  });

  it("smooths sharp spikes toward neighboring heights", () => {
    const terrain = createTerrain({
      id: "terrain-smooth",
      position: { x: 0, y: 0, z: 0 },
      sampleCountX: 3,
      sampleCountZ: 3,
      cellSize: 1,
      heights: [0, 0, 0, 0, 10, 0, 0, 0, 0]
    });

    const smoothedTerrain = applyTerrainBrushStamp({
      terrain,
      center: { x: 1, z: 1 },
      settings: {
        radius: 1.5,
        strength: 1,
        falloff: 0
      },
      tool: "smooth"
    });

    expect(smoothedTerrain.heights[4]).toBeLessThan(10);
    expect(smoothedTerrain.heights[4]).toBeCloseTo(10 / 9);
  });

  it("flattens toward the stroke-start reference height", () => {
    const terrain = createTerrain({
      id: "terrain-flatten",
      position: { x: 0, y: 0, z: 0 },
      sampleCountX: 3,
      sampleCountZ: 3,
      cellSize: 1,
      heights: [0, 0, 0, 0, 4, 0, 0, 0, 0]
    });

    const flattenedTerrain = applyTerrainBrushStamp({
      terrain,
      center: { x: 1, z: 1 },
      settings: {
        radius: 1.2,
        strength: 0.5,
        falloff: 0
      },
      tool: "flatten",
      referenceHeight: 2
    });

    expect(flattenedTerrain.heights[4]).toBeCloseTo(3);
  });

  it("returns zero influence outside the brush radius", () => {
    expect(getTerrainBrushWeight(2, 1, 0.5)).toBe(0);
  });
});