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Course Review #159
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NPR 1The instructions provided don't lead to the target shader. Following the instructions leads to the answer found here; however, the target shader on the left does not match. It seems that on the left the light source moves with the cursor, but on the right the shader obtained by following the exercise directions has the light source fixed. Visually, the "edges" formed between two bands looks like it stays in the same position on the dragon model. |
I really like the course. Congratulations to the authors!! I'm not sure what the goal and the target audience are, so ignore my comment if it's inappropriate. Maybe the course could be even greater if you added a couple of hints or exercises with the most common mathematical solutions used in shaders (that in most cases appear to be taken for granted). At least those a bit more advanced than the absolute basics. For example, expecting a beginner to know about rotation matrices (i guess that's a quaternion?) in the first vertex shader exercise (ironically called "The Basics" :) is a bit ambitious. That was impossible for me and i suppose it could be the same for many computer graphics beginners. But that was great for me to learn (watching the answer). At the end of the day, i think that maybe 90% of CG problems are solved with a limited combination of trigonometry functions. Personally, i'd really like to see those strategies (and others) explicitly exposed in a course on shaders. |
Exercise 15 geom-4 was a very hard jump for me too, and I gave up and cheated :( |
I'm only up to exercise 11 now, but I'll agree with @krzychukula on exercise 10. I ended up making all of the trigonometry calculations manually. Is there really a rot() function??? Anyway, the materials don't really guide towards the desired solution. Exercise 12 I've gotten working by just making another varying vec for color and then assigning it in both shaders. Basically 3 lines of additional code - although my initial solutions involved actual calculation of the vertices and setting appropriate formulas for calculating the colour at any given point. Neither of these seems correct, although the first one does pass. |
To further clarify on what I pointed out above, from Exercise 12:
The solution requires neither of these to be done, as long as you have the color attribute, fragColor varying and then set that automatically interpolated value in the fragment shader. No calculation of vertices or colours is required since it is done automatically. |
I find the following articles helpful for the exercise 15 geom-4. https://math.stackexchange.com/questions/2235997/reflecting-ray-on-triangle-in-3d-space |
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Exercise 4
There was no info about "&&" in the previous lessons.
I would start with information that you can use && like in JS (preferably with short code sample)
In my opinion shuld be extended with something like:
to make sure it's obvious what is the type of the result.
Then in "boolean vectors" I would appreciate if it would be explained when and why should I use all/any functions.
Something like:
"Instead of writing
p.x && p.y && p.z
on bvec3 you can use handy function:all(p)
that will do the same thing.I may add feedback to other lessons here but feel free to close it earlier.
Exercise 5
Actually I had to change it to
i<=100
to make it work and I wasn't something I was expecting:Exercise 6
It would be great to have a reminder somewhere that I can't use n in
for(int i = 0; i < N; i++)
and I have to use static numberfor(int i = 0; i < 16; i++)
#104 helped a lot :)
Exercise 7
Something about
length
ordistance
or just link to the documentation would help a lot.Exercise 8
frag-2
There is no info which color to set if fragments is not discarded, but the only one that worked was:
gl_FragColor = vec4(1,1,1,1);
Exercise 10
I had no idea how to solve it.
I would say this one is really to hard, even looking at the result it's not clear what really happens here or why multiplication is the same as rotation... Really confusing.
Exercise 13 geom-2
Exercise 14 geom-3
Link to https://en.wikipedia.org/wiki/Scaling_(geometry) would be helpful
Exercise 15 geom-4
No idea where where to get this:
If it's obvious easy to find then maybe there should be some required reding before?
Light 1
"That is, there is some parameter called kA which just determines the color of each fragment."
ambient
parameter is supposed to determine color.Light 2
All in all fragment shader was pretty easy but I had no idea how to create fragNormal and that I needed worldNormal not to menion how to create it.
Light 3
Just to hard for me :(
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