16-721: Learning-based Methods in Vision Staff: Instructor: Alexei (Alyosha) Efros 4207 TA: Jean-Francois Lalonde A521 NSHJean-Francois Lalonde Web Page: urses/LBMV07/ urses/LBMV07/

Today Introduction Why This Course? Administrative stuff Overview of the course Image Datasets Projects / Challenges

A bit about me Alexei (Alyosha) Efros Relatively new faculty (RI/CSD) Ph.D 2003, from UC Berkeley (signed by Arnie!) Research Fellow, University of Oxford, ’03-’04 Teaching I am still learning… The plan is to have fun and learn cool things, both you and me! Social warning: I don’t see well Research Vision, Graphics, Data-driven “stuff”

PhD Thesis on Texture and Action Synthesis Antonio Criminisi’s son cannot walk but he can fly Smart Erase button in Microsoft Digital Image Pro:

Why this class? The Old Days™: 1. Graduate Computer Vision 2. Advanced Machine Perception

Why this class? The New and Improved Days: 1. Graduate Computer Vision 2. Advanced Machine Perception Physics-based Methods in Vision Geometry-based Methods in Vision Learning-based Methods in Vision

Describing Visual Scenes using Transformed Dirichlet ProcessesTransformed Dirichlet Processes. E. Sudderth, A. Torralba, W. Freeman, and A. Willsky. NIPS, Dec The Hip & Trendy Learning

Learning as Last Resort

from [Sinha and Adelson 1993] EXAMPLE: Recovering 3D geometry from single 2D projection Infinite number of possible solutions!

Learning-based Methods in Vision This class is about trying to solve problems that do not have a solution! Don’t tell your mathematician frineds! This will be done using Data: E.g. what happened before is likely to happen again Google Intelligence (GI): The AI for the post-modern world! Why is this even useful? Even a decade ago at ICCV99 Faugeras claimed it wasn’t!

The Vision Story Begins… “What does it mean, to see? The plain man's answer (and Aristotle's, too). would be, to know what is where by looking.” -- David Marr, Vision (1982)

Vision: a split personality “What does it mean, to see? The plain man's answer (and Aristotle's, too). would be, to know what is where by looking. In other words, vision is the process of discovering from images what is present in the world, and where it is.” Answer #1: pixel of brightness 243 at position (124,54) …and depth.7 meters Answer #2: looks like bottom edge of whiteboard showing at the top of the image Which Do we want? Is the difference just a matter of scale? depth map

Measurement vs. Perception

Brightness: Measurement vs. Perception

Proof!

Lengths: Measurement vs. Perception Müller-Lyer Illusion

Vision as Measurement Device Real-time stereo on Mars Structure from Motion Physics-based Vision Virtualized Reality

…but why do Learning for Vision? “What if I don’t care about this wishy-washy human perception stuff? I just want to make my robot go!” Small Reason: For measurement, other sensors are often better (in DARPA Grand Challenge, vision was barely used!) For navigation, you still need to learn! Big Reason: The goals of computer vision (what + where) are in terms of what humans care about.

So what do humans care about? slide by Fei Fei, Fergus & Torralba

Verification: is that a bus? slide by Fei Fei, Fergus & Torralba

Detection: are there cars? slide by Fei Fei, Fergus & Torralba

Identification: is that a picture of Mao? slide by Fei Fei, Fergus & Torralba

Object categorization sky building flag wall banner bus cars bus face street lamp slide by Fei Fei, Fergus & Torralba

Scene and context categorization outdoor city traffic … slide by Fei Fei, Fergus & Torralba

Rough 3D layout, depth ordering

Challenges 1: view point variation Michelangelo

Challenges 2: illumination slide credit: S. Ullman

Challenges 3: occlusion Magritte, 1957

Challenges 4: scale slide by Fei Fei, Fergus & Torralba

Challenges 5: deformation Xu, Beihong 1943

Challenges 6: background clutter Klimt, 1913

Challenges 7: object intra-class variation slide by Fei-Fei, Fergus & Torralba

Challenges 8: local ambiguity slide by Fei-Fei, Fergus & Torralba

Challenges 9: the world behind the image

In this course, we will: Take a few baby steps…

Goals Read some interesting papers together Learn something new: both you and me! Get up to speed on big chunk of vision research understand 70% of CVPR papers! Use learninig-based vision in your own work Try your hand in a large vision project Learn how to speak Learn how think critically about papers

Course Organization Requirements: 1.Paper Presentations (50%) Paper Presenter Paper Evaluator 2.Class Participation (20%) Keep annotated bibliography Ask questions / debate / flight / be involved! 3.Final Project (30%) Do something with lots of data (at least 500 images) Groups of 1 or 2

Paper Advocate 1.Pick a paper from list That you like and willing to defend Sometimes I will make you do two papers, or background 2.Meet with me before starting, to talk about how to present the paper(s) 3.Prepare a good, conference-quality presentation (20-45 min, depending on difficulty of material) 4.Meet with me again 2 days before class to go over the presentation Office hours at end of each class 5.Present and defend the paper in front of class

Paper Evaluator For some papers, we will have Evaluators Sign up for a paper you find interesting 1.Get the code online (or implement if easy) 2.Run it on a toy problem, play with parameters 3.Run it on a new dataset 4.Prepare short min presentation detailing results 5.Discuss the paper critically

Class Participation Keep annotated bibliography of papers you read (always a good idea!). The format is up to you. At least, it needs to have: Summary of key points A few Interesting insights, “aha moments”, keen observations, etc. Weaknesses of approach. Unanswered questions. Areas of further investigation, improvement. Submit your thoughts for current paper(s) at the end of each class (printout)

Class Participation Be active in class. Voice your ideas, concerns. You need to participate JF will be watching and keeping track!

Final Project Can grow out of paper presentation, or your own research But it needs to use large amounts of data! 1-2 people per project. Project proposals in a few weeks. Project presentations at the end of semester. Results presented as a CVPR-format paper. Hopefully, a few papers may be submitted to conferences.

End of Semester Awards We will vote for: Best Paper Presenter Best Paper Evaluator \Best Project Prize: dinner in a nice restaurant

Course Outline

Datasets See web page