- The writing of this paper is very misleading. First of all, it claims that it can be trained only using a single viewpoint of the object. In fact, all previous diffrentiable rendering techniques can be trained using a single view of object at training time. However, the reason why multi-view images are used for training in prior works is that single-view images usually lead to ambiguity in the depth direction. The proposed method also suffers from this problem -- it cannot resolve the ambiguity of depth using a single image either. The distrance-transformed silhouette can only provide information on the xy plane - the shape perpendicular to the viewing direction. - I doubt the proposed method can be trained without using any camera information (Line 223, the so called "knowledge of CAD model correspondences"). Without knowing the viewpoint, how is it possible to perform ray marching? How do you know where the ray comes from? - The experiments are not comprehensive and convincing. 1) The comparisons do not seem fair. The performance of DVR is far worse than that in the original DVR paper. Is DVR trained and tested on the same data? What is the code used for evaluation? Is it from the original authors or reimplementation? 2) Though it could be interesting to see how SoftRas performs, it is not very fair to compare SoftRas here as it use a different 3D representation -- mesh. It is well known that mesh representation cannot model arbitrary topology. Thus it is not surprising to see it is outperformed. Since this paper works on implicit surface, it would be more interesting to compare with more state-of-the-art differentiable renderers for implicit surface, i.e. [26],[27],[14], or at least the baseline approach [38]. However, no direct comparisons with these approaches are provided, making it difficult to verify the effectivenss of the proposed approach.
- I doubt the proposed method can be trained without using any camera information (Line 223, the so called "knowledge of CAD model correspondences"). Without knowing the viewpoint, how is it possible to perform ray marching? How do you know where the ray comes from?