Function sphere

src/resource/mesh.cpp:422–472

Finds the tightest bounding sphere by calling add_points() multiple times on the same randomly ordered positions. Uses a seed dependent on initial positions to guarantee stable results.

	// randomly ordered positions. Uses a seed dependent on initial positions to guarantee stable
	// results.
	static Sphere sphere(Geometry &g)
	{
		const u32 MAX_TRIES = 256;
		Sphere sphere;
		sphere::reset(sphere);

		if (array::size(g._positions) != 0) {
			const u16 seed = (u16)murmur64(array::begin(g._positions)
				, array::size(g._positions)*sizeof(g._positions[0])
				, 0u
				);
			Random random((s32)seed);

			Array<f32> positions(default_allocator());
			Array<u32> indices(default_allocator());
			array::resize(positions, array::size(g._positions));
			array::resize(indices, array::size(g._positions) / 3);

			for (u32 j = 0; j < array::size(indices); ++j)
				indices[j] = j;

			Sphere s;
			for (u32 i = 0; i < MAX_TRIES; ++i) {
				sphere::reset(s);

				// Shuffle index.
				for (u32 i = 0; i < array::size(indices); ++i) {
					s32 k = random.integer(array::size(indices));
					exchange(indices[i], indices[k]);
				}

				// TODO: just add a sphere::add_points() that supports index buffers.
				for (u32 i = 0; i < array::size(indices); ++i) {
					positions[i*3 + 0] = g._positions[indices[i]*3 + 0];
					positions[i*3 + 1] = g._positions[indices[i]*3 + 1];
					positions[i*3 + 2] = g._positions[indices[i]*3 + 2];
				}

				sphere::add_points(s
					, array::size(g._positions) / 3
					, sizeof(g._positions[0]) * 3
					, array::begin(positions)
					);

				if (sphere::volume(s) < sphere::volume(sphere) || i == 0)
					sphere = s;
			}
		}

		return sphere;
	}

	s32 write(Mesh &m, CompileOptions &opts)
	{