Render Texture (Render Texture) is a technical term that is extremely important in rendering and optimizing game graphics (technical art). A technology that stores camera drawing results in video memory like regular texture assets, and draws them on the surfaces of 3D objects in the game in real time.
Real-world analogy: The process of constantly recording live footage from a security camera onto a ``dedicated monitor videotape (VRAM area)''
The mechanism behind Render Texture is ``A mechanism that continues to overwrite and record the live footage from a sub camera every frame onto a ``dedicated videotape (texture buffer)'' that is directly connected to the TV screen.'' The images captured by the camera are sent to this videotape (RenderTexture) and saved, instead of being projected directly onto the screen. By setting that videotape as a "texture" on the 3D TV or magic mirror material in the game, you can freely project the world on the other side of the mirror and the images on the surveillance monitor into the 3D scene in real time.
Figure: An infographic that clearly illustrates the basic processing flow and mechanism of Render Texture (Render Texture) in Japanese notation
Detailed mechanism and operating principle
Create a new "Render Texture" asset in the project, assign it to the "Target Texture" property of the sub camera, and paste the render texture to the 3D display material in the game.