7. Constraints: Interpreting Line Drawings

MIT 6.034 Artificial Intelligence, Fall 2010
Instructor: Patrick Winston

How can we recognize the number of objects in a line drawing? We consider how Guzman, Huffman, and Waltz approached this problem. We then solve an example using a method based on constraint propagation, with a limited set of junction and line labels.

License: Creative Commons BY-NC-SA

[richarddow]

This is priceless, a history lesson, a creation lesson, a process lesson, and deep insight into vision. MIT OCW you are angels.

[yuxuanliu]

Many love to Patrick Winston. He just passed away this Summer. Thanks for the great courses you given, it was an honor to be your student

[nikolahuang]

I want to clarify how to distinguish the concave, convex, and boundary lines.
1. If you see 2 faces on each side of a line, then the line is a concave or convex line, depending on the angle of the 2 faces: angle > 180 is convex, and angle < 180 is concave.
2. If you see 1 surface on a side of a line, on another side, it is space, air, or nothing, then, the line is a boundary line. The way to determine the direction of the arrow on the line: the surface(object) you see is always on the right side of the arrow.
i.e. if the arrow points to left in a horizontal boundary line, then the surface(object) is above the line;
if the arrow points to up in a vertical boundary line, then the surface(object) is on the right side of the line.

If I am not clear enough, leave a message here to ask me.

[LanceBryantGrigg]

This blew my mind. cool. The more I watch this course the more I want to binge watch it like an addictive TV series.

[chrisminnoy]

What's amazing is that the professor knows the names of his students.

[lawjibran]

for right going or left going boundary its like walking on the boundary in a direction such that the whole object always falls on that right hand than that boundary is in the direction of the walk.

About octants its like the joint vertex is on (0, 0, 0) in a standard x y z coordinates system and the edges are on x, y or z axes

Stuff off the object just means the whole object.

Covex lines are just lines joining two surfaces that from our perfective their outer faces has more than 180 angles and its less than 180 for concave, by outer faces i mean surfaces faces that are visible to us

[niksfeb]

The prof's program said that the drawing at 47:55 was unambiguous and could represent only one scenario but i think 2 are possible.
1. A viewer watching a staircase normally such that goes from the left to the right
2. A viewer watching a staircase from below it such that it goes from left to right

[arthurpopulaire]

Very helpful. I have a course that requires me to learn this and this made it very clear. Thanks.

[thumbsmeup]

If you listen closely at 46:42, somebody tries to cover up their fart by coughing and fails horrendously.

[ghassensmaoui]

Did not manage to figure out criteria according to which we classify a line as concave or convex.

[olgxofg]

Hoffman is a genius. Once the 4 line types and 18 possible junctions are laid out, the rest is clear.

[ShivangiSingh-wcgk]

I am finding this hard to grasp, is there any other resource one can suggest to understand this?

[xXxBladeStormxXx]

"Back when men were men" :D
Real men take at least 4 physics, and at least 4 math courses.

[Leon-pnrb]

21:02 How are 2 convex and one concave?
Shpuldnt they all be concave ?

[lifetheuniverse]

showing a sketchup 3d the model @ 30:00 that could really exist

[ashnur]

Whatever is in the cup, it's strong.

[kyoungd]

Elegant, yes.  Simple no.  Well, at least it wasn't simple for me.  Still, this is MIT, and their students are the brightest of our country.  Quite fascinating.  I always wondered how machine vision worked.

[jlbaraky]

why cant exist a arrow with 2 bondaries and 1 concave? at 19.:18 you can see in this perspective

[kernadan]

"Back when Men were Men " Preach it brother.

[erichlf]

The most important question: what kind of chalk is that?