Category: computer-graphics

ô ăn quan

| Categories: computer-graphics, cs & it | Tags:
Có 50 quân dân, và 2 quân quan, mỗi quan tương đương 10 dân. Người chơi có quyền chọn di chuyển theo hướng bất kỳ, những game Mancala khác chỉ được di chuyển theo một chiều nhất định.

Ăn quân ở ô kế tiếp trong lượt đi chứ không phải ở ô đối diện của đối phương. Khi đến lượt mình mà không còn quân để đi thì phải bỏ 5 quân đã ăn được vào 5 ô của mình để tiếp tục chơi. Trường hợp không có đủ 5 quân thì phải vay của đối phương và trả lại khi trò chơi kết thúc.

Trò chơi dân gian Việt Nam Ô ăn quan thuộc họ Mancala, có nguồn gốc châu Phi và có hàng chục biến thể khác nhau trên thế giới. Khi nhỏ, tôi có chơi trò này vài lần, gọi theo tên địa phương là Ô làng chứ không phải Ô ăn quan. Hôm nay thử nhìn cái game này dưới góc độ tin học xem sao! Ô ăn quan có một số luật khác với những game Mancala khác.

Những luật bên, nhất là luật thêm & mượn quân làm Ô ăn quan phức tạp hơn nhiều so với những biến thể Mancala khác. Viết một chương trình cho máy tính chơi Ô ăn quan không phải là quá dễ dàng, dùng những heuristic đơn giản (hill-climbing, min-max, hay brute-force đến một độ sâu nhất định…) không đủ bảo đảm máy tính sẽ thắng trong nhiều trường hợp.

Trên internet, tôi không tìm được game Ô ăn quan nào theo đúng luật Việt Nam. Một số là những biến thể gần giống Ô ăn quan, một số tác giả claim là đã viết Ô ăn quan nhưng không cung cấp được link download. Có vẻ như game này không dể như khi vừa mới nghĩ đến! Bạn nào có ý kiến về chiến thuật chơi game này xin được trao đổi để cùng phát triển một trò chơi hoàn chỉnh.

Bên đây là screenshot của một Java applet tôi vừa viết trong vài tiếng đồng hồ, cho phép 2 người chơi với nhau (máy tính chỉ kiểm luật, chưa phải là một chương trình cho máy tính chơi thực sự). Những hiệu ứng đồ họa: di chuyển quân, ăn quân nhìn rất giống thật, graphics được vẽ bằng Photoshop: những viên sỏi và bàn chơi được vẽ bằng phấn trên mặt sân xi-măng… gợi lại những kỷ niệm thủa nhỏ.

minesweeper

| Categories: computer-graphics, cs & it | Tags:

Two more hours of work and I’ve added this hexagonal tiles to my MineSweeper! Anyone interested in the game can found the tiny binary and source code (450 LOC) here. Mine sweeping with hexagons is quite a different experience! More about MineSweeper, a simple game?

On the left: Minesweeper with hexagonal tiles

virtualization

| Categories: computer-graphics, cs & it, linux | Tags:

MineSweeper running in DOSBox

Click the demo page below (jpcapplet.jar – 1.8 MB in size), it would take some times to load, embedded in it is a DOS image (floppy.img) of a floppy’s size (1.4 MB). In Linux, using dd to create a blank image file, launch JPC app, mount the empty image, fdisk to give it a partition structure, format to give it a bootable FAT12 file system, copy the files over, edit autoexec.bat to have the game run at startup, and voila – there you are, the classic DOS game of MineSweeper on the web!

Beside is screen-shot of my very first programming, the classic MineSweeper, an exercise I did first year at university. After getting started with Borland C++ 3.1, I began to write numerous toys like this; small games, graphics, animation, 3D… are among the things I was very fond of. We still had not had Internet in Vietnam then, lacking of information, we’d reinvented many wheels, including a package for displaying 3D objects (in form of polygon mess), a complete GUI for DOS with window, menu, toolbar, all kinds of controls: combo, list, button… But as they say: don’t reinvent the wheel, unless you plan on learning more about wheels, the reason we did all that fun stuff.

Back to my MineSweeper, it’s tiny, about 350 LOC (Line Of Code), using BGI (Borland Graphics Interface), C/C++ and some ASM. Yesterday, just want to check the old source, but didn’t have a Windows machine at hand, I needed to run the Borland C++ 3.1 compiler on my Linux box. Wine is good for many Windows applications, but it simply won’t work with pure DOS programs. Then I found DOSBox, you start it up in form of a console, mount a directory in local file system, have BC 3.1 installed and compiles flawlessly, and MineSweeper runs well on this virtual DOS on top of Linux!

That’s some layers of virtualization, say I want more, I want to show MineSweeper on the web, but don’t want to make change to the code, or even to the compiled binary. Could it be possible? The answer is: YES! You would need JPC, a pure Java IBM-PC emulator, it runs where there is Java: x86, RISC, mobile phone… On top of it, you can run a bundle of different OS: DOS, Linux, Windows… Then comes the delicate distinction between virtualization and emulation, hardwares, softwares, all can be virtualized to some great extent. Imagine you would run some games & utilities on a virtual DOS (or Linux) running inside JPC, hosted in Firefox browser, which in turn runs on Windows (or Linux)!

JPC can only bring about 20% power of the native machine, and even a tiny game like this is overkill to it, and mouse functioning is really crappy too. But that’s suffice to demonstrate the idea, JPC could be improved I believe. More games would be added to this Web DOS console later on! Anyone still remember Tetris, Croix-Zero, Snake, Mario…? So, what’s the points for JPC? Demonstrating the fractal principles in hardware, software evolution? Too much “nostalgia” for the “good old days” – DOS games? Anything else or just reinventing the wheel? The answer may be so, but I love this idea of cultivating the past, and pop out new things for the future!

math expression on www

| Categories: computer-graphics, cs & it, linux

I rarely need to write mathematics expressions on the web, but the last time I did, it took me some times to figure out just how to do. It’d turned out to be pretty easy, there’s a free LaTeX rendering server at yourequations.com. Excellent site! Just feed it with a LaTeX expression, it would render an image for you to put on your web page. This may be the best solution for now, while waiting for an workable HTML version that supports math.

There’s also a guide to embed this feature onto Blogger blogs (and also WordPress, and some PHP forums…) Just insert your LaTeX code between the pre (or code) tags as below and the jsTeXrender JavaScript would do the rest for you. This works fine for any browser with JavaScript support (mouse over the expressions and you would see the underlying LaTeX code). You may also need this LaTeX Reference Card for a list of LaTeX’s symbols.

Update, Otc 1st, 2010

Due to heavy traffic, yourequations.com has ceased the service. Please see this new post on how to run a LaTeX rendering server of your own!

CMS 2.0 released

| Categories: computer-graphics, cs & it

Some typical UI features:

Data & input validation using XPath

Custom-drawn combobox (with check-box item)

Custom-drawn grid with tens of thousand cells

Simple vector object editing

Custom-draw tree with loading effect

The CMS project, in which I’m the team leader, has come to it’s second phase, with major features completed. Although I felt tired with the on-going work, it’s my most beloved product. CMS (short for Central Management System) serves as a gateway through which clients manage the DVR Servers (Digital Video Recorder). The product demonstrates many technologies & programming techniques, just to name a few:

  • IOCP (IO completion port): the multi-threaded IOCP server has proved to be very efficient, hundreds of concurrent connections won’t rise CPU usage to higher than 5%. However, the connections are stateless, it’s best that we would add a state-machine to better control the traffic.

  • TCP + XML communication: we devise a draft protocol like XML-RPC or SOAP, which bases on TCP rather than HTTP.

  • XML data storage: all network command & data is presented in XML. With version-numbered XML, we hope to solve the backward compatibility problem ever existed with so many releases of our main DVR products.

  • XML processing is made easy thank to the wonderful TinyXML and TinyXPath libraries. I must emphasize that XPath makes XML processing much more feasible, it greatly reduces the number of LOC (line of code) and procedural complexity.

  • A sophisticated client MFC GUI demonstrates various GUI programming techniques, almost every tricks with MFC GUI has been gathered in this product: heavy custom-draw controls, flicker-freed rendering, advanced input validation…

  • Some borrowed concepts from other flatforms: the elegant “signal & slot” are added to handle complicated interaction between GUI’s elements (in addition to MFC’s message queue mechanism).

I have some lessons learned after the project:

  • It’s a MUST that you have a team with members of the same professional level. This would make sure the members would easily understand each others and share a common culture.

  • C/C++ is still a MUST for real time programming tasks (it’s “half-civilized nature” makes it a strong language). And the use of some matured flat-form: boost, wxWidget… would greatly help the developing process.

  • It’s only by the desire for creation & creativity that programmer would offer an excellent product. The culture of a developing team is somewhat like honey-bees, who collect pollen little by little to make honey and wax.

I’ve been involved in many projects, some is more interesting, some is more difficult than this one. But this is the first one that I’d made, everything from A to Z. It’s now time to leave I3 but I must say this is the project that I loved and two years at I3 was a special time in my career! Looking at the screenshots below, you would see that CMS is very rich in it’s designs about information presentation.