Rotation, combined with translation and scaling, are the three affin transforms we do every day in the 3D nutshell universe. The rotation itself, however, is somehow much more complicated than the other two transform, it is one really needs a matrix representation among all three. Representations and computation of it has been developed for years. We have systems like Axis-angle representation, matrix representation, euler angles and quaternions. Despite I have known them for a long time, when I forgot, the rotation is still complicated. Here I am writing this again, as easily understanding as possible, for my future-self (or I can just travel through time to ask myself now).

I have been trying to create a animation system for my OpenGL Project for a long time, one of the reason is I have limited amount of time after starting the full-time job. Another problem was that, I mean, if I intend to keep it a clean project rather than just a school project, building a animation system is like a rabbit hole, 30 lines of code got me another 100 lines of work, it only leaded me deeper and deeper. Well, it is a perfect opportunity for me to explain the story here. The amount of skeletal animation that I found online, especially good blogs are less than a dozen. Gladly, I would like to point it out here, there is a good youtube video series you can follow, it is in Java, the author provided the source code for reference. Khronos has a shader example here and there are a few others.

Template is a confusing and hard features in C++ if you want use it well, and I think it is also one of the reason which causes c++ programmers cannot understand each other. Sometimes the Deduction rule for c++ is really confusing, you don’t understand why you code doesn’t work or why it works. And Since STL heavily uses nesting Templates, both your compiler and your mind suffers from that.

The MVP Matrix

$\text{Model} * \text{View} * \text{Projection}$ is the first lesson to render (the so called render is the process so that people can see it on a 2D screen )objects in Computer Graphics, which transfer a 3D object in object space into, in the end, a UV plane.

The Model matrix is simple and easy to understand, simply the translation, scale and rotation, but View matrix and Camera matrix are not obvious(although you can get it for free by single call from glm::lookAt() and glm::perspective()).

It is 2016, low level coding is not needed anymore. We have programming languages like javascript and python. When people code everything with a class and related methods. But do you remember we have a programming language called C? When we had no class, templates, operator-override or implicit constructor at esthat time. You actually know what are doing with C, no magic!

I claim no expert to programming, since I only have a four-year-old programming life. But even you are inexperienced like me, you should still be able to code some thing in C. IT IS fatigue to code in C, you have no standard containers to rely on, you spend 10 hours to build a perfect deque data type which works on amortized O(1) complexity and has no memory leaks before you are able to work on your project. Awesome!!! But why? Why try to build a huge robust data structure in a non-OOP language? Instead of trying simulate constructors and destructors, you could always use a double pointer to do the job. Have you ever seen Linus Torvalds’s double pointer code? It removes on special case where you would make mistakes.

I have been studying in programming for 6 years, since my first day of undergrad life. I haven’t realized it has been so long, this studying life already took away most of my youth. I was a kid without knowing the toughness of life, to a young man need to worry about jobs and how to start having family.

The computer industry changed vastly in this period. There was no Cloud Computing, Machine Learning was only known in Academics. Universities taught students how to code in VC++. Now everything is different.

这是我的第一篇github上的博客，感觉落后时代好多年啊。因为完成自己的博客生成器不 久。所以写的第一篇博客就以生成我的博客站点的项目mkblogs说起，来说说如何写一个 博客生成器吧。