CS148 Program 1 FAQ

Project 1 FAQ

Q: I want to add ovals/filled circles/rotated rectangles to my project. How much extra credit will that be worth?
A: Project 1 extra credit FAQ:
In terms of primitives, let's say:
- Defining a "good" rotated rectangle from three clicks (tricky, since three points don't necessary define a rectangle, so you need to do a little math) and drawing its edges will be three points.
- Drawing an unfilled parallelogram - which you can draw from three points - will be one point of extra credit (you just need to generate one new point and connect the points with your line routine)
- Filling rotated rectangles or parallelograms will be three points, provided you use a Bresenham-like approach. Hint: you can use Bresenham's line algorithm to walk along the edge of your rectangle and draw a multiplication-free horizontal line at each row to make this work. It's the same work to fill rectangles or parallelograms, so you won't get six points for doing both.
- Filling circles will be three points, as long as you use a Bresenham-like approach (again, you can combine Bresenham for circles with line-drawing to make filled circles). You should still only need to run Bresenham (i.e. compute decision variables) for one octant.
- Unfilled ovals will be five points for a Bresenham-like approach (no points for a brute-force approach equivalent to the brute- force circle approach we started with on the lecture slides). I think this one will be quite tough; you'll have to re-derive the decision variable equations. I don't recommend this one.
And let's put a maximum of 8 extra credit points for things on this list.
If you do any new primitives, make sure that by default the program works just like the demo. If I want filled circles, for example, I should have to press a button to go into "filled circles mode"; I should still get unfilled circles in 'circle mode'.
Five points if you let the user define a clipping rectangle and implement Cohen-Sutherland for lines. This sounds like a lot of work, but the code is literally on the lecture slides (the actual C code), so this might not be too bad.
All of these values assume that the extra credit works correctly in all cases, etc. I.e., a broken implementation of circle-filling may not get any extra credit.
Also a reminder that there's one point of extra credit on the line for the best minipaint file, but make sure that you document any new .minipaint files in your README, otherwise we may never see them.
Maximum 15 points total extra credit.
Make sure to document all extra credit in your README.

Q: I think there is a bug in the stencil code. It doesn't work right when I do [fill in the blank].
A: We'll be updating bugfixes on this FAQ -- check it often. Unless it is really serious, we won't release new stencil code (since hopefully you've all started editing your code). If you don't find mention of it here, e-mail the course staff and we'll look into it.
Q: The airbrush mode in the compiled program provided seems to require mouseDrag, since it actually tracks where the mouse has been and fills in those points. But in the sample code, it says we don't need to look at the mouseDrag function. Is that extra credit, then, and normal credit is just whatever point is clicked on first?
A: You don't need to call your flood-fill from the mouseDrag function. It's not really extra credit, since all you have to do is call the your floodfill function from the mouseDrag function, which we've already given you and registered with GLUT. But IMO it's much more satisfying to drag the airbrush around than to just click on individual points.
Q: Do we need to implement the floodfill-by-runs algorithm, or will a non-recursive, per-pixel algorithm be okay?
A: You are only required to do the pixel-based, non-recursive algorithm. Doing the algorithm that uses horizontal runs is worth 3 points of extra credit (out of 100).
Q: Can we use our floodfill algorithm to fill our rectangles?
A: No, this will be unpleasantly slow and won't work in certain cases. There's a hint in the handout that suggests a good way to fill your rectangles.
Q: Are we graded on code style?
A: You will not be graded on style; the only things we'll look at in a working program's code are what we need to see to make sure you used Bresenham's algorithms and a non-recursive floodfill.
If you give all your variables offensively profane names and put your entire program in capital letters, you'll still get full credit as long as your program works and we can confirm that you implemented the right algorithms.
Q: Why is there garbage in the window when I start up the program? (BUG #1)
A: There is a missing glFlush() in redraw(). Just put glFlush() at the end of the function. Note that this causes the window to clear itself when it resizes, which is the intended behavior.