A Framework for Fast Low-Power Multi-sensor 3D Scene Capture and Reconstruction

We present a computational framework, which combines depth and colour (texture) modalities for 3D scene reconstruction. The scene depth is captured by a low-power photon mixture device (PMD) employing the time-of-flight principle while the colour (2D) data is captured by a high-resolution RGB sensor. Such 3D capture setting is instrumental in 3D face recognition tasks and more specifically in depth-guided image segmentation, 3D face reconstruction, pose modification and normalization, which are important pre-processing steps prior to feature extraction and recognition. The two captured modalities come with different spatial resolution and need to be aligned and fused so to form what is known as view-plus-depth or RGB-Z 3D scene representation. We discuss specifically the low-power operation mode of the system, where the depth data appears very noisy and needs to be effectively denoised before fusing with colour data. We propose using a modification of the non-local means (NLM) denoising approach, which in our framework operates on complex-valued data thus providing certain robustness against low-light capture conditions and adaptivity to the scene content. Further in our approach, we implement a bilateral filter on the range point-cloud data, ensuring very good starting point for the data fusion step. The latter is based on the iterative Richardson method, which is applied for efficient non-uniform to uniform resampling of the depth data using structural information from the colour data. We demonstrate a real-time implementation of the framework based on GPU, which yields a high-quality 3D scene reconstruction suitable for face normalization and recognition.