Flow Map (Flow map / Flow map) is a technical term that is extremely important in the rendering and optimization of game graphics (technical art). An explanation of a lightweight shader technology that uses texture RGB values as two-dimensional "movement vectors (flow direction and speed)" to freely flow water surfaces, magma, gas, clouds, etc. by dynamically deforming UV coordinates.
An example in the real world: A flow guide system in which a ``road map (vector map) with arrows indicating the direction and speed of water flow'' is laid out on the surface of a river, and the texture of the water surface continues to flow while automatically distorting in the direction of the arrow
Stop mindlessly scrolling through the entire water surface texture, and follow the instructions of the arrows (RG vectors) on the flow map, saying things like "Avoid the flow to the right around this rock" and "Make the flow twice as fast here" pixel by pixel. By dynamically instructing the deformation (texture distortion) of href="/article/term-uv-coordinates-details">UV coordinates and blending and fading the texture over time (reset processing using sawtooth waves), we create a realistic river flow that avoids rocks without using even 1mm of polygons or physical calculations.
Diagram: An infographic that clearly illustrates the basic processing flow and mechanism of Flow Map (Flow Map / Flow Map) in Japanese notation
Detailed mechanism and operating principle
Prepare a "Flow Map (Flow Map texture)" that depicts the direction of the vector in red (velocity in the U direction) and green (velocity in the V direction), and dynamically distort the texture by adding the offset of this vector to the UV coordinates every frame on the shader side.