mmooss
a year ago
I should know this in order to post on HN, but I hope someone will explain: In mathematics, what is the difference between a grid, tiling, packing, and tessellation?
I've read several sources without forming a precise answer. My best guess is that a grid is about the lines formed by and forming tiling polygons; tiling is about polygons (assuming 2-d) filling a space; packing is filling a space with a defined polygon (again if 2-d) whether or not it's filled completely; and tessellation is a form of tiling that requires some kind of periodicity?
Edit: I forgot 'packing'!
abetusk
a year ago
Some of these terms are pretty general and their usage will depend on the user and context. I'll try to define what I think are the most appropriate and common usages of each.
Grid - usually a regular D-dimensional boxes that are packed, axis aligned. Sometimes used synonymously with a set of points that are also regularly placed and axis aligned. I've used this to describe a (finite) rectangular cuboid (in 3D) but could just as easily be used to describe an infinite set of boxes. As in "Label each cell in the grid an alternating color of red or blue".
Tiling - A covering of some D-dimensional space from a (finite) set of smaller tiles, with no overlap and no gaps. I've used this to describe higher dimensional spaces but is often used for 2D. As in "A set of Penrose tiles can be used in a plane tiling".
Packing - Placing a (finite) set of smaller geometric elements into a large area such that the geometry doesn't overlap but gaps are allow. The larger area that can be be finite or infinite. The dimension can be arbitrary. This is often used in context of trying to minimize the gaps within the area being packed. As in "Randomely placing 3D oblong spheroids (aka 'M&Ms') in a box of side length L will yield a sub-optimal packing. Introducing gravity, friction and 'shaking' the box for some amount of time will yield a better packing"
Tesselation - A synonym for tiling.
A grid is a tiling. For example a 2d grid is a tiling/tesselation of the plane by boxes.
hinkley
a year ago
Tessellation is more clever tiling. In general you get fairly simple concavities in tiling, like darts or deltas, whereas tessellation typically has compound inclusions that require being assembled from outside the plane.
In the real world you can usually push tiles into place, but tessellated objects have to be dropped in place from above, like puzzle pieces. Or I suppose grown in place if it’s organic.
mmooss
a year ago
Many thanks!
> Grid - usually a regular D-dimensional boxes that are packed, axis aligned.
Can grids include gaps?
abetusk
a year ago
In my opinion, no. Sorry for the confusing term, I should have used something else.
Here I meant "packed" as in "packed tightly with no gaps". Maybe I should have used the term "tiled" instead.
Note that, in my opinion, common usage is axis aligned but this need not necessarily be the case. "Hex grids", for example, are non axis aligned [0].
thechao
a year ago
A grid is a set of points, described by a basis. A tiling is like puzzle pieces, but with a fixed number of piece "shapes". A packing is a way to stuff a set of things into a space. Tilings and packings are related, but the subfields are asking different questions.
dexwiz
a year ago
Tilings cover an entire plane with no gaps or overlaps. Opposed to packings which may leave gaps.
smokel
a year ago
You may also like: lattice.
mmooss
a year ago
Thank you! I do.
itronitron
a year ago
I may be wrong but I think 'packing' may allow the shapes to vary in size.