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| Wed 25 Jun 08 - GLSL specular shader |
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I've been playing with GLSL for a week now and the first think I've tried to make was a specular shader. OGL's fixed functionality produces very ugly speculars in low geometry so pixel shaders is the only solution. I've searched the net to find a spec shader but nothing was good enough and in terms of visuals and from speed's standpoint. Im not a GLSL guru but some optimizations are pretty obvious even for me. Anyway I present you a specular program witch contains a speed hack.
Shader specs are. Phong shading for one light (the GL_LIGHT0) using the material properties and combines the light result with 2 textures. The files bellow have detailed comments.
vertex shader
fragment shader
screenshot without textures
Enjoy!
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| Mon 16 Jun 08 - Invert square root (invsqrt) in 64bit compilers/architectures |
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Invert square root, or simply invsqrt, is a mathematical function that calculates the "1/square_root(x)" expression of a given number 'x'. The function's origin is uncertain but it believed that 3Dfx invented it many years back. After that, John Carmack used it in quake engine and when the source of the engine got published the invsqrt made its way to the masses. The awesomeness of this functions is that its really really fast, faster than computing the "1/sqrt(x)". The most common use of invsqrt is in computer graphics and especially in vector normalization. The version found in Carmack source is the following:
float InvSqrt( float f )
{
float fhalf = 0.5f*f;
int i = *(int*)&f;
i = 0x5F3759DF - (i>>1);
f = *(float*)&i;
f *= 1.5f - fhalf*f*f;
return f;
return 1/sqrtf(f);
}
...unfortunately this version uses a trick that it is relying in 32bit architecture and if someone tries to compile it in 64bit the result will be incorrect. So I sat down and replaced the sensitive code with inline assembly and here is the result:
float InvSqrt( float f )
{
float fhalf = 0.5f*f;
asm
(
"mov %1, %%eax;"
"sar %%eax;"
"mov $0x5F3759DF, %%ebx;"
"sub %%eax, %%ebx;"
"mov %%ebx, %0"
:"=g"(f)
:"g"(f)
: "%eax", "%ebx"
);
f *= 1.5f - fhalf*f*f;
return f;
}
The code is for the GNU C/C++ compiler and its probably compatible with 32bit architectures.
Enjoy! |
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| Sun 11 May 08 - Valve's Steam distribution service and PC piracy |
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What is Valve's Steam? In sort its a digital distribution service. In Steam you can buy and then download PC games, play multiplayer, see your friends, and many more. Its also a must platform for idle developers. Steam helps them to present their work in a wider audience. Among the many advantages that Steam offers is that it might become the savior of PC gaming.
What about the current state of piracy? Piracy was always a problem in both PC and consoles. The setting changed rapidly in the recent years though. The new generation of consoles become more secure (PS3 cant run copies at all for example) but the PC didn't changed that much. Actually in PC the piracy got worst because of the constant rise of fast internet connections. The result of this changes are catastrophic. Most of the games ship first on consoles and after some months on PC, or not at all. Its also sad to see our favourite PC franchises to get "consolish" in order to harmonize with the console audience (UT3 for example).
How Steam will help to minimize piracy? This may occur in multiple ways. Valve's marketing director Doug Lombardi gave a very interesting interview some time ago about this matter. He said a Steam-like services can eliminate the "Day Zero" piracy. According to Doug the damaging piracy happens between gold and when the game's on the store shelves. Simply put, this means that the gamers find the new game release first in the torrent sites and later in the stores. Not everyone has the patience to wait, apparently. Steam on the other hand has an activation system in witch both of the versions (both retail and Steam) get activated at the official release date. This activation system holds back the crackers cause they have to work not before the official release date. A second advantage of Steam is that it eliminates a few costs and fees. If we analyze the price of a game in a self we can find fees for the developer, the publisher, multiple retailers, shipment cost, package cost etc. A game on the Steam doesn't have retailer's fees, shipment and packaging costs. So more money go the the rightful owners. A third good thing is that Steam helps idle developers with no or limited funds.
Is everything bright? Actually its not. The pricing for the games in Steam is wayyyy to high. At least for Europe. Steam games are some euros cheaper than the retail versions. So why bother buying from Steam when you can get the complete package at the same price? Personally I never consider buying something from Steam. In US the things are different. Another thing is that I haven't seen a game (beside Valve's) using Steam's activation method.
Many things need to be done for PC gaming to stay alive. The future holds many surprises or many disappointments. We'll see |
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| Fri 09 May 08 - Migrating to Ubuntu 8.01 64bit - Part III |
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The idea of migrating from Windows to Linux always appealed to me but sometimes this kind of change is a very difficult task. So, in the past few weeks I was trying to learn if Linux (Ubuntu) was suitable for my personal needs. I'm a PC user with interest especially in programming, web authoring, surfing the internet, playing games, listening to music, watching movies. Some of those needs fit easily in the new OS some others not. Lets see what's our current progress.
Programming: In Win I was using VisualC++. In Linux and for now I use Code::Blocks with GCC. Code::Blocks is a fine IDE but it lacks the VC++ debugging capabilities (among others). I've also tried KDevelop witch I found very very loaded for no apparent reason, tons of files buttons and crap. For now Code::Blocks is ok but for the future I may need to learn to use make, vim and some better debugger. The first task for me in Linux was to port a 3D engine project Im making. The engine is in C++, OpenGL and SDL so I thought that it will be a piece of cake to port from VC++ to GCC. I was totally mistaken. This task proved to be a pain in the ass for a few days. The problem? I had to rewrite my math library cause I was getting tons of errors. Apparently there were some incompatibilities with some complex operator overloading and I think that this is because of M$. M$ never learned to respect the standards. Fortunately Ive port the engine and its working fine. Later I will try to port the code back Win again. If its not working in Win this time, I will change profession, I will become a farmer.
Web authoring: Php, mysql and Apache work fine in Linux even If didnt tried to install them yet. In web authoring I was using Photoshop but I didn't managed to install it in wine.
Surfing the internet: Firefox before Firefox now. Nothing changed. I even copy/pasted my windows profile in Linux and it worked just fine. The only problem is the crappy Flash plagin. Its slow in fullscreen and sometimes it crashes.
Playing games: Games is out of the question in Linux for now. I installed my copy of Doom3 though. It runs with no errors but I thing its slower than the Win version.
Listening to music: I use Amarok in Linux. Its not winamp but for me is fine.
Watching movies: I use Ubuntu's default media player and VLC. After some testing "Movie Player" is slow in HD formats, sometimes it shows the vids corrupted and finally it crashes when you move the progress bar (in some vids). On the other hand VLC is solid but it doesn't plays files located the network. Apparently VLC doesn't support Samba.
I havend login in Windows XP partition for quite some time now. I hope it will stay that way. I really like Ubuntu. |
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| Fri 02 May 08 - Ubuntu 7.10 64bit, the final thoughts! - Part II |
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After some time playing with Ubuntu 7.10 64bit I end up being a little disappointed. The first appeal was great but after working with 64bit I found tons of bugs. The “Tracker” was buggy, for some reason the memory consumption was constantly rising, the ColdFusion had problems with windowed OpenGL applications (blender)... and a few more bugs I cant recall right now. The majority of the bugs I found was only in 64bit, apparently the 32bit is more stable.
At this time the new version of Ubuntu is out and I will check this too... soon |
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