Using multiple materials in deferred shading can present several challenges:

1. Complex Material Management: Deferred shading requires the separation of geometry and lighting passes. This means materials need to be represented in a way that can be efficiently processed in the lighting pass, often requiring multiple textures and parameters to be stored in the G-buffer.

2. G-buffer Size and Performance: Each material might have different properties such as diffuse color, specular highlights, normals, and other surface characteristics. Storing all these properties for multiple materials can increase the size of the G-buffer, which impacts memory usage and bandwidth, potentially reducing performance.

3. Limited Material Flexibility: Since the G-buffer has a fixed format, adding new material properties or supporting complex materials can be challenging. It requires careful planning and might necessitate changes in the G-buffer layout, which can be costly in terms of performance.

4. Lighting Complexity: Deferred shading excels at handling many lights, but the complexity of lighting calculations can increase with diverse material properties. Each material might react differently to light, requiring more complex shaders and potentially increasing computational load.

5. Transparency Handling: Deferred shading struggles with transparency, as it typically requires multiple passes or forward rendering techniques. Managing multiple materials with varying transparency can complicate the rendering pipeline.

6. Shader Complexity: Supporting a wide variety of materials necessitates complex shader logic to interpret and apply the correct material properties during the lighting pass. This can lead to more intricate and harder-to-maintain shader code.

7. Debugging and Development Overhead: With multiple materials, debugging becomes more challenging due to the complexity of the rendering pipeline. Developers need to ensure that all material properties are correctly written to and read from the G-buffer, which can be error-prone.

Addressing these challenges often involves trade-offs between visual fidelity, performance, and development complexity.