Unsupervised Single-Image Intrinsic Image Decomposition with LiDAR Intensity Enhanced Training

Unsupervised intrinsic image decomposition (IID) is the task of separating a natural image into albedo and shade without ground truth during training. Although a recent model employing light detection and ranging (LiDAR) intensity demonstrated impressive performance, the necessity of LiDAR intensity during inference restricts its practicality. To expand the usage scenario while maintaining the IID quality achieved by using both an image and its corresponding LiDAR intensity, we propose a novel approach that utilizes an image without LiDAR intensity during inference while utilizing both an image and LiDAR intensity during training. Specifically, our proposed model processes an image and LiDAR intensity individually using distinct encoder paths during training, but utilizes only an imageencoder path during inference. Additionally, we introduce an albedo-alignment loss aligning the gray-scale albedo from an image to that from its corresponding LiDAR intensity. LiDAR intensity is not affected by illumination effects including cast shadows, thus albedo-alignment loss transfers the illumination-invariant property of LiDAR intensity to the image-encoder path. Furthermore, we also propose image-LiDAR conversion (ILC) paths that mutually translates the style of an image and LiDAR intensity. IID models translate an image into albedo and shade styles while keeping the image contents, thus it is important to separate the image into contents and style. Trained with pairs of an image and its corresponding LiDAR intensity which share contents but differ in style, the mutual translation in ILC paths improve the accuracy of the separation. Consequently, our model achieves comparable IID quality to the existing model with LiDAR intensity, while utilizing only an image without LiDAR intensity during inference.