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Derek Zeng

A programmer

About FYP

by coderek

My FYP hasn’t had any progress for a while already. I should say I was kind of unfamiliar with my code after December holiday, so a lot of time now are spent reading code and documentations. My current task is to implement the sleep function in client side. This requires me to look at client code, and turn off wifi card there when server command is sent over. The wifi card can easily be turned off on Linux, so I have to switch to Linux now.

Linux is in fact a very good thing. Although, it doesn’t have very powerful tools, its simplicity complement any disadvantage it has. For example, making a system call is just one line of code. Its default packages are so developer friendly that, I can compile code in any way I like easily. Of course, the pre-requisite is I understand the working of the system.

So basically what I want to do for my FYP is to turn off wifi for certain duration when command is sent over. It’s of course a line of code to do that in Linux.

    system(‘rfkill block wifi)’)

But before that, in fact I have to do many things. Here are some I need to figure out:

  • send command from server to client
  • simulate client packets when his wifi is turned off
  • store sleep information and time on both server and client
  • switch on and off sleep state on both server and client side

The previous guy who were doing similar algorithm actually left some code I can refer to. But it seems to me that his code is not so reliable. This is because he didn’t do off-line packets simulation and he put sleep information inside the client connection structure. Moreover, he didn’t discover the PVS algorithm, so I assume he didn’t really understand the Quake3 code before doing anything. Though his code is unreliable I still benefit from reading his code in some way.

For example, Quake3′s makefile is huge, and I really have no idea where to add my scan file in. His makefile did help figure out this. And he’s also use SV_SendServerCommand function, this conform with my observation. However, he receive command at the wrong place and didn’t acknowledge the command thus, will cause overflow hence leading to disconnection. So I correct this by putting command reception inside CL_GetServerCommand. So I have fixed the 1st problem.

The 3rd, and 4th problem seems easy for me, I should solve those first. Then I should attempt the 2nd. Hopefully, Quake3 code has implemented some function to do off-line packets simulation, so I can make use of it. Otherwise, I would be troublesome to do playerState update on my own.

It seems that these stuff is pretty easy to do, but that’s not true. It really takes me a while to fully understand the Quake3 architecture. Michael Abrash’s ‘The Big Picture’ did help me a lot. And I like what he said, “There are a million ways not to finish a project, but there’s only one way to finish: Put your head down and grind it out until it’s done.” It inspires me when I feel frustrated.

There still lies a long road to go for my FYP. The goal is to make my algorithm work perfectly without any glitch. By then, I should have fully understand the Quake3 code. One part of Quake3 that pose great interest to me is the renderer part. I am only able to spend a little time looking at the render. Though it uses OpenGl, very few native gl functions are actually exposed. Or maybe, I haven’t found the correct place to look at. I will look at that after this project.

(End of article)