Deferred shading is a rendering technique that allows for efficient handling of many lights in a scene by separating the lighting calculations from the geometry rendering. Here's how it works:

1. Geometry Pass: In the first pass, the scene's geometry is rendered to a set of textures known as the G-buffer. This buffer typically contains information like positions, normals, albedo (base color), and specular properties for each pixel. Importantly, no lighting calculations are done in this pass.

2. Lighting Pass: In subsequent passes, lighting calculations are performed using the information stored in the G-buffer. For each light source, the lighting effect is computed only for the visible pixels, significantly reducing the number of calculations compared to forward rendering, where lighting is computed for each vertex or fragment for every light.

3. Efficiency with Many Lights: Deferred shading is particularly efficient when dealing with a large number of lights because:

   • Decoupled Lighting: Since lighting is calculated in a separate pass, the cost of adding additional lights is reduced. Each light only affects the pixels that are visible and relevant, rather than requiring a full scene pass.
   • Scalability: The lighting calculations can be optimized for the area of influence of each light, allowing for techniques like light culling or screen-space optimizations to further enhance performance.

4. Memory and Bandwidth Considerations: While deferred shading can handle many lights efficiently, it requires significant memory bandwidth due to the need to store and read from the G-buffer. This can be a limitation on systems with less memory bandwidth.

Overall, deferred shading is a powerful technique for scenes with complex lighting, allowing for realistic and dynamic illumination without the prohibitive cost of traditional forward rendering methods.