are created using a Z-axis instead of Y-axis normal, so rotate it
				planeMesh.rotation.x = -Math.PI / 2;
				planeMesh.position.y -= 20; // Mirror the same Y offset used on the HeightField above
				planeMesh.geometry.computeVertexNormals();
				planeMesh.material.needsUpdate = true;

				bodyInterface.AddBody(terrain.GetID(), Jolt.EActivation_Activate);
				scene.add(planeMesh);

				// Create a bunch of spheres to drop on the terrain
				const position = new Jolt.RVec3(0, 0, 0);
				for (let y = 0; y < 