Midterm 2 Marking Comments

The midterms are marked and the grades are in WebCT. Here are some comments on the way I marked them.

I must admit I had to go through these more quickly, so if you are unsure of why you lost marks somewhere because I didn't write much, let me know.  If you think your answer deserves more marks or that I missed something in determining the correctness of your answer, send an email that demonstrates this. If indeed I think you deserve more marks, I’ll ask you to bring in your midterm paper.

Be sure to check my addition!

Note: The prof said that as long as you didn’t go over the number of questions allowed for each section I could count all the marks for those questions, even if it takes you over 90. I am hoping this was clear for you during the exam, especially because this wasn't the case for the first one.

Number 1

In 1.1, I want to see specifics, especially what function is applied and what you do with the result of that function (add to the height of vertices). Being too general gets you 2/5. If you didn’t mention what the output of the wave function is doing you lost one mark.

In 1.2, the full formula is:
height = amplitude * sin (wavelength * distanceFromSource + angularFrequency*time + shift)
I am taking off 0.5 each for missing wavelength, angular frequency and shift and 1 for missing the others (amplitude, distance from source, and time). Same amount for missing or incorrect explanations. The height/sin part of the equation is worth 1 mark. If you added any terms that shouldn’t be there, I took off 0.5.

In 1.3, the idea is to find which source a particular wave is closer to – that will be the distance used to compute the vertex height. If you correctly did something that added the heights from the two waves together, we are giving marks (12/15).

Number 2

In 2.2, if you only talked about normals needing a proper transformation when transformations like shear are applied, you got 3/7. I needed to know what happens and why it matters in more detail (normals won’t be perpendicular, lighting will be wrong, etc).

Number 4

Forgetting to discuss 2-3 operations for the shaders will lose you 2 points each for 4.1 and 4.2.

Forgetting to state output for 4.1 and 4.2 loses you 1 mark.

Number 5

In 5.1, half marks are given for a reasonable discussion that shows a misunderstanding of the lighting components.

In 5.3, if you say that vertex shaders can be used to do bump mapping but don’t say how (as in, where are you going to get info on how to modify normals, such as from a texture), I took off 1 mark.

Number 6

In 6.1, getting the wrong R vector results in two marks lost (especially if I can’t see how you computed it).

In 6.3, if you forget the surface material value you lose 1 mark, and if you forget the source light you lose 1 mark. If you don’t normalize V and R you lose 1 mark.

Ask Your Questions Today

Just a quick note to say that tomorrow, unfortunately, I will be in Toronto last-minute for a family illness and likely won't be able to answer your questions regarding the assignment.  So be sure to ask as much as you can today! Also, if enough of you could check WebCT through the day tomorrow, you may be able to help each other in the discussion forums.

Sorry about this!

Assignment 4 Clarification

I have confirmed a couple of things about the assignment that many of you were wondering about.  First of all, before starting task two, you should set the scaling of the earth object to be (1,1,1) again.  Answer all the questions up until 4.2 using this value.  Then change it to (0.1, 1, 0.1).  The question about what issue you observe and how to fix it is directly related to the midterm question on world inverse/tranpose matrix.  An answer of "don't scale it that way" is not correct, because of course you might actually want to scale it that way.  Think about what happens with the normals when you scale the sphere and whether they remain perpendicular to the surface.

Upcoming Grading Plans

Assignment 4

My first task is to actually do the assignment so that I can better answer some of your questions before it's due.  This will also make it easier to mark the midterm (and of course the assignment itself).  I am still waiting for confirmation about some of the issues you brought up regarding the assignment questions, and when I know more I will post here.

I will be grading the assignment after the midterms, so you probably won't see your mark back for these until the first full week of December or so.

Midterm

The plan is to have the grades up on WebCT by the end of the day Tuesday November 29, which should be in time to decide to drop the course if needed.  Depending on exactly when I finish, you might get the papers back in class Tuesday, or Thursday at the latest.

The Best Midterm Tip I Can Give...

...is to work on Assignment 4.  Trying to understand all the pieces and at least starting to code them will be invaluable.

Also be sure to have a good understanding of all the questions given as samples on the course webpage.

Remember, if you have any questions about any of these things, please ask sooner rather than later so I'll have time to give you a decent answer!

Clarification from Tutorial

During our informal tutorial, I pointed out that a position (VPOS) was indeed available to be passed in to a pixel shader.  However, it is not the vertex's position as I may have said or implied, but rather the pixel's position on the screen.  If you wanted to know where that pixel would have been in the 3D world, you would indeed need to "cheat" by passing the information in some other way (possibly using texture coordinates, as the prof was suggesting).

Give Your TA Feedback

A few TA's in SCS (myself included) are participating in voluntary feedback through the TA Mentorship program.  The idea is to collect your thoughts on how we're doing both so we can improve and so we can have a record of our performance.

You can leave feedback on the participating TA's with this convenient online form.  I'd love to get your feedback about me. :)

Informal Tutorial Update 2

Room has been booked! Our informal tutorial will take place here:

HP 4325
12:00pm - 1:00pm
Thursday, November 10, 2011

Informal Tutorial Update 1

Hey all, I'm working on getting a room booked for our informal tutorial.  So far Thursday this week is the best day for most people, but our SCS seminar room is taken, so I'm trying for a nice room in the Math department.  If I can't find anything, I might try for something on the following Monday.  Watch this space and I'll update with a new post as soon as I know more.

Informal Tutorial: Help Pick a Time

Fill in this poll if you are interested in an informal tutorial to help you prepare for the second midterm:

http://www.doodle.com/pvy7tn9zn225fnmp

Please only fill in the days you know you will be able to attend.

Assignment 3 Marked

The third assignment is now marked and on WebCT.  Overall, most of those who attempted it did well.  A few general comments:

• There were a few assignments that looked suspiciously similar.  It might have been a coincidence (and it might have carried over from the previous assignment, and I just didn't notice it then).  But just in case it is not, please be more careful in the future.  Your best bet is to make a note of who you worked with on an assignment when you submit if you did indeed work together.
   
• There are still some basic code-related issues (so I made sure there were some marks for that).  For instance, I want to continue to get you to use good practices like making your class members protected or private, not using the 'this' pointer to access your members unnecessarily, and avoiding magic numbers.
   
• Please remember to clear all your warnings before submitting!
   
• And check whether you check your project file for this stuff before submitting.  You don't want to make your TA do more work than she has to before she even starts grading. ;)  I'll take marks off in the future if I have to modify it for you.

Two-Kings DirectX Tutorials

A student mentioned using this site for their texture tutorial, and since it looks useful I figured I'd share:

http://www.two-kings.de/

If you have any great DirectX resource websites, comment here or send them to me so I can share with everyone else as well.