Geometry Shader (Geometry shader) is a technical term that is extremely important in rendering and optimizing game graphics (technical art). Immediately after the vertex shader, this is an explanation of an advanced shader stage that dynamically creates and destroys polygon vertex data in real time inside the GPU, and generates a program from mere "points" to "boards (polygons)" and "solids" on the spot.
Real-world analogy: When assembling parts (points) in a factory, a 3D printer is turned on the spot to ``create new parts (polygons) on the spot'' and ship them on a magical extended assembly line
Geometry shader is "a real-time alchemy of polygons that magically multiplies and transforms 'vertices' into 'triangles' on the spot on the GPU assembly line after receiving the skeleton of a 3D model, and instantly erases unnecessary polygons". By using this, by simply passing a flat triangle, the GPU can automatically create and draw a large number of ``thorns'', ``blades of grass'', and ``splatters of flying sparks'' from its boundaries on the spot, allowing you to express an infinite number of precise details while keeping the game's data size completely at zero.
Illustration: Geometry Shader (Infographic that clearly illustrates the basic processing flow and mechanism of geometry shader) in Japanese notation
Detailed mechanism and operating principle
Write a Geometry Shader (Geometry Shader), and from the coordinates of "one point on the ground" passed from the vertex shader, create a triangular "grass polygon" (Billboard)' is generated, ejected and drawn in real time.