Add unit tests for spline corridor junction mesh generation

tests/geometry/spline-corridor-junction-mesh.test.ts

@@ -0,0 +1,189 @@
+import { describe, expect, it } from "vitest";
+
+import { createScenePath } from "../../src/document/paths";
+import { createSplineCorridorJunction } from "../../src/document/spline-corridor-junctions";
+import {
+  buildSplineCorridorJunctionFootprint,
+  sampleSplineCorridorJunctionFootprintInfluence
+} from "../../src/geometry/spline-corridor-junction-footprint";
+import { buildSplineCorridorJunctionMeshGeometry } from "../../src/geometry/spline-corridor-junction-mesh";
+
+function createRoadPath(
+  id: string,
+  points: Array<{ x: number; y?: number; z: number }>
+) {
+  return createScenePath({
+    id,
+    road: {
+      enabled: true,
+      width: 2,
+      shoulderWidth: 1,
+      heightOffset: 0.1
+    },
+    points: points.map((point, index) => ({
+      id: `${id}-point-${index}`,
+      position: {
+        x: point.x,
+        y: point.y ?? 0,
+        z: point.z
+      }
+    }))
+  });
+}
+
+describe("spline corridor junction mesh generation", () => {
+  it("builds a connection-shaped footprint from clipped corridor boundaries", () => {
+    const pathA = createRoadPath("path-junction-footprint-a", [
+      { x: 0, z: 0 },
+      { x: 10, z: 0 }
+    ]);
+    const pathB = createRoadPath("path-junction-footprint-b", [
+      { x: 5, z: -5 },
+      { x: 5, z: 5 }
+    ]);
+    const junction = createSplineCorridorJunction({
+      id: "junction-footprint",
+      center: { x: 5, y: 0, z: 0 },
+      radius: 3,
+      connections: [
+        {
+          pathId: pathA.id,
+          progress: 0.5,
+          clipDistance: 2
+        },
+        {
+          pathId: pathB.id,
+          progress: 0.5,
+          clipDistance: 2
+        }
+      ]
+    });
+
+    const footprint = buildSplineCorridorJunctionFootprint({
+      junction,
+      paths: [pathA, pathB]
+    });
+
+    expect(footprint).not.toBeNull();
+    expect(footprint?.points).toHaveLength(8);
+    expect(footprint?.bounds).toEqual({
+      minX: 3,
+      maxX: 7,
+      minZ: -2,
+      maxZ: 2
+    });
+  });
+
+  it("builds junction fill geometry from the connection footprint instead of a circle", () => {
+    const pathA = createRoadPath("path-junction-mesh-a", [
+      { x: 0, z: 0 },
+      { x: 10, z: 0 }
+    ]);
+    const pathB = createRoadPath("path-junction-mesh-b", [
+      { x: 5, z: -5 },
+      { x: 5, z: 5 }
+    ]);
+    const junction = createSplineCorridorJunction({
+      id: "junction-mesh",
+      center: { x: 5, y: 0, z: 0 },
+      radius: 3,
+      connections: [
+        {
+          pathId: pathA.id,
+          progress: 0.5,
+          clipDistance: 2
+        },
+        {
+          pathId: pathB.id,
+          progress: 0.5,
+          clipDistance: 2
+        }
+      ]
+    });
+
+    const geometry = buildSplineCorridorJunctionMeshGeometry({
+      junction,
+      paths: [pathA, pathB]
+    });
+    const positionAttribute = geometry?.getAttribute("position");
+
+    expect(positionAttribute?.count).toBe(9);
+    expect(Array.from(positionAttribute?.array ?? [])).toEqual(
+      expect.arrayContaining([
+        3,
+        expect.closeTo(0.1, 5),
+        -1,
+        7,
+        expect.closeTo(0.1, 5),
+        1,
+        4,
+        expect.closeTo(0.1, 5),
+        -2,
+        6,
+        expect.closeTo(0.1, 5),
+        2
+      ])
+    );
+  });
+
+  it("samples full terrain influence inside the connection footprint and falloff outside it", () => {
+    const pathA = createRoadPath("path-junction-influence-a", [
+      { x: 0, z: 0 },
+      { x: 10, z: 0 }
+    ]);
+    const pathB = createRoadPath("path-junction-influence-b", [
+      { x: 5, z: -5 },
+      { x: 5, z: 5 }
+    ]);
+    const junction = createSplineCorridorJunction({
+      id: "junction-influence",
+      center: { x: 5, y: 0, z: 0 },
+      radius: 3,
+      connections: [
+        {
+          pathId: pathA.id,
+          progress: 0.5,
+          clipDistance: 2
+        },
+        {
+          pathId: pathB.id,
+          progress: 0.5,
+          clipDistance: 2
+        }
+      ]
+    });
+    const footprint = buildSplineCorridorJunctionFootprint({
+      junction,
+      paths: [pathA, pathB]
+    });
+
+    if (footprint === null) {
+      throw new Error("Expected a junction footprint.");
+    }
+
+    expect(
+      sampleSplineCorridorJunctionFootprintInfluence({
+        footprint,
+        x: 5,
+        z: 0,
+        falloffDistance: 1
+      })
+    ).toBe(1);
+    expect(
+      sampleSplineCorridorJunctionFootprintInfluence({
+        footprint,
+        x: 2.5,
+        z: 0,
+        falloffDistance: 1
+      })
+    ).toBeGreaterThan(0);
+    expect(
+      sampleSplineCorridorJunctionFootprintInfluence({
+        footprint,
+        x: 1,
+        z: 0,
+        falloffDistance: 1
+      })
+    ).toBe(0);
+  });
+});