The term "rice grain" is misleading, there are no grains in there.
The western name for this pattern comes possibly from the grain shapes used in the pattern.
This is pattern was made at least since the early 19th century, and it is still being manufactured. It is found mainly on thin dishes, bowls, spoons or cups, but not on larger items, usually.
A porcelain item with formed shape has the pattern cut out from the clay, making an empty space in the clay.
When the item is glazed the transparent glaze fills the grain-like shapes. Afterwards the firing and decoration is completed as usual. The fired item has now pattern with grain-like transparent shapes.