Sprites - Poor man's 3D rendering

Modeling stuff like Trees, explosions in 3D is excessively complex. The number of polygons used to render them make it prohibitively expensive even for high end cards. So most games take shortcuts to create approximations, which are nearly as good, but extremely cheap. One such concept is sprites...

The basic idea behind sprite is that, no matter how much u model, the final image appears on the 2D screen. So technically you can get away with just rendering the 2D view of it. So how do you do this? simple, just draw one polygon with the 2D view of the object, and then make sure that the Polygon is *ALWAYS* facing the user. so no matter which place in the 3D world the user looks at from, he sees the same side of the polygon facing him. This gives a reasonable illusion of 3D for a very very cheap CPU and RAM cost! Obviously this works best only for objects which do not require much interaction with the user, and are mere eye candy.

Adrian now implements sprites, and litters the map with some trees here and there. Another thing is that although a tree looks complex, we just render a single rectangle. We take an image of a tree, in which parts of it not inside are made transparent (instead of some color), and saved as a TGA file (JPEGs etc do NOT support transparency). Now we map the image to the rectangle, and it gives the illusion of a tree.

For the OpenGL coders, to do this you have to enable transparency use the following code

    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

However if 2 or more transparent objects overlap, then the results will result in the one drawn first getting hidden by the later drawn one (even IF the first object is in front of the other!). To overcome this order the objects need to be distance sorted.

If distance sorting is not an option, then my friend Vamsi suggested that you can enable Alpha Test to make sure that before overwriting the buffer, OpenGL compares the existing alpha value and if lesser does not overwrite the existing one.

    glEnable(GL_ALPHA_TEST);
    glAlphaFunc(GL_GREATER, 0.5);

Adrian on Windows

So we do realize that there are too many developers for windows platform, who want to get their hands dirty with our code.. or so we hope they exist. Since we use SDL it was an easy ride from linux to windows. Head over to the adrian code base and get the updated files and visual studio 9 project files. Btw.. you will ofcourse need SDL_mixer, SDL, SDL_image and SDL_ttf dev libraries and runtime dlls to get the project to compile under windows as well.

Known Issues:
1) Textures of some of the enemies loaded in the game look weird.
2) Lot of warnings during compilation.

Ps: We do not have any releases yet... so you will have to use svn clients to get your hands on the game code.

Code ONLINE!

The code for Adrian Game is now licensed under GPLv3 and is available at Google Code. The hosting facility appears to be pretty good. We will be making changes to it and improving it, as well as fix existing bugs. If you know of any bugs, do send me a mail or just start a new issue in the issues tab in google code.

Adrian Resurrected!

Adrian game was initially developed by Suman Korada, V Vamsi Krishna and myself, while we were in 3rd year B.Tech at IIIT-Hyderabad in 2003. We wrote the game for a game designing contest in 7 days (and nights) flat. The initial version that you see is based off the same source code. Needless to say it was pretty impressive and we walked off with the first prize :).

After almost 6 years of no development on it (mainly since we could not afford the better graphics cards initially and later working full time), I felt like it was a good time to resurrect the project and here we are. The actual trigger for resurrecting adrian came from a guy who mailed me about the game saying he liked it. It prodded me to download the source code myself and see how it runs, and I was very impressed with our work. There were a lot of changes which we could not do for the contest since, we were operating under a severe time constraint then. But now the development can proceed at a more slower pace.

I am very excited about this new game, and hope I will have as much fun as I had last time I used it.