Using cross-polarization in a multi-camera 3D photogrammetry station helps to eliminate specular reflections and capture more accurate texture details. Here's why it matters:

1. Removes Unwanted Highlights

• Glossy surfaces (like skin, plastic, or metal) create specular highlights that shift based on the camera angle.
• These highlights are view-dependent, meaning they can interfere with consistent texture generation across multiple images.
• By eliminating these reflections, photogrammetry software gets clean, diffuse textures that align better across all cameras.

2. Enhances True Color and Detail

• Specular reflections wash out fine details and alter colors in the captured images.
• Cross-polarization preserves subsurface details (e.g., skin pores, fabric texture) by filtering out glare.
• This results in higher fidelity albedo textures, useful for 3D models in VFX, gaming, and digital humans.

3. Improves Photogrammetry Accuracy

• Photogrammetry relies on feature matching between multiple images.
• Reflections create false features that confuse algorithms and lead to errors in the 3D reconstruction.
• Removing reflections ensures better depth estimation and a cleaner point cloud.

How It Works

• Polarizing filters are placed on both the light sources and the cameras.
• The light's polarization is aligned in one direction, and the camera filters are rotated 90 degrees to block any reflected light.
• This effectively removes glare and specular highlights while keeping the diffuse component of the material.

Trade-offs

• Cross-polarization reduces overall brightness, so more powerful lights or higher ISO settings may be needed.
• It removes specular highlights, which may be useful for material property reconstruction (e.g., roughness, reflectivity).