How do we get pseudo labels from unlabeled images?
Unlike classification, directly thresholding the network outputs for dense prediction doesn't work well.
Our idea: start with weakly sup. localization (Grad-CAM) and refine it with self-attention for propagating the scores.
Using two different prediction mechanisms is great bc they make errors in different ways. With our fusion strategy, we get WELL-CALIBRATED pseudo labels (see the expected calibration errors in E below) and IMPROVED accuracy under 1/4, 1/8, 1/16 of labeled examples.
Evaluation of VOC12 and COCO datasets show consistent improvement over the supervised approach under different portions of labeled examples.
One cool thing is that our method can also further improve fully supervised models trained on a FULL DATASET with additional *unlabeled* data.
Isn't that awesome?
Check out the more details in the paper, supp material, and code.
NeRF has shown incredible view synthesis results, but it requires multi-view captures for STATIC scenes.
How can we achieve view synthesis for DYNAMIC scenes from a single video? Here is what I learned from several recent efforts.
Instead of presenting Video-NeRF, Nerfie, NR-NeRF, D-NeRF, NeRFlow, NSFF (and many others!) as individual algorithms, here I try to view them from a unifying perspective and understand the pros/cons of various design choices.
Okay, here we go.
*Background*
NeRF represents the scene as a 5D continuous volumetric scene function that maps the spatial position and viewing direction to color and density. It then projects the colors/densities to form an image with volume rendering.
Have you ever wondered why papers from top universities/research labs often appear in the top few positions in the daily email and web announcements from arXiv?
Why is that the case? Why should I care?
Wait a minute! Does the article position even matter?
The method achieves AWESOME results but requires precise camera poses as inputs.
Isn't SLAM/SfM a SOLVED problem? You might ask.
Yes, it works pretty well for static and controlled environments. For causal videos, existing methods usually fail to register all frames or produce outlier poses with large errors.
How can we learn NeRF from a SINGLE portrait image? Check out @gaochen315's recent work leverages new (meta-learning) and old (3D morphable model) tricks to make it work! This allows us to synthesize new views and manipulate FOV.
Training a NeRF from a single image from scratch won't work because it cannot recover the correct shape. The rendering results look fine at the original viewpoint but produce large errors at novel views.
Congratulations Jinwoo Choi for passing his Ph.D. thesis defense!
Special thanks to the thesis committee members (Lynn Abbott, @berty38, Harpreet Dhillon, and Gaurav Sharma) for valuable feedback and advices.
Jinwoo started his PhD in building an interactive system for home-based stroke rehabilitation. Published at ASSETS 17 and PETRA, 2018.
The preliminary efforts lay the foundation for a recent 1.1 million NSF Smart and Connected Health award!
He then looked into scene biases in action recognition datasets and presented debiasing methods that lead to improved generalization in downstream tasks [Choi NeurIPS 19]. chengao.vision/SDN/