Open Gl

sleepygamer213 · Sep 4, 2005

Is open GL any better than D3D? If i downloaded something for Open GL would it run BETTER than D3D? Because right now i know my OPEN GL runs worse than D3D..

earlthemailman · Sep 4, 2005

how do you tell what you have? i have a radeon 9800 pro 128 agp. what is the difference between the open gl and d3d?

ACE 256 · Sep 4, 2005

you have both ....newer games tend to run better in D3D...will older games run better in openGL .....openGL and D3D are included in windows ( thow thare are older versions...)

Omegamerc · Sep 4, 2005

Also, a new extension of Open GL is being released.

sleepygamer213 · Sep 4, 2005

Interesting... got a link?

theven 4 · Sep 4, 2005

what is open gl???

sleepygamer213 · Sep 5, 2005

a software based graphics renderer. A very interesting read follows, if i do say so myself

OpenGL is without a doubt the prevailing industry API for developing 2D and 3D graphical applications. It can be considered the successor to the formidable Silicon Graphics IRIS GL-library which made so popular SGI workstations as the predilect platform for scientific, engineering and special effects development. SGI put into OpenGL a great deal of their expertise to make an easy-to-use, intuitive, portable and network aware API for the future. At the same time we can credit SGI for realizing the importance of open standards. Several hardware and software makers took part in OpenGL's specification and stand behind it. Thanks to this, OpenGL applications can be ported quite easily to virtually any platform in the market, from PC windows95, to our glorious Linux system, high-end UNIX workstations, right up to mainframe supercomputers. The Architectural Review Board oversees OpenGL specifications, accepting or rejecting changes and proposing conformance tests.

In contrast to the old IRIS GL-library of SGI, OpenGL is by design, platform and operating system independent. It is aware of the network, so it is possible to separate our OpenGL application into a server and a client which actually renders the graphics. There is a protocol to move through the network OpenGL commands between server and client. Thanks to its OS independence, server and client do not have to run on the same type of platform. Quite commonly the server may be a supercomputer running a complex simulation and the client a simple workstation mostly devoted to the graphical visualization. OpenGL allows developers to write applications that can be easily deployed across many platforms.

Above all OpenGL is a streamlined, high-performance graphics rendering library and there are many graphic accelerator cards and specialized 3D cards that implement OpenGL primitives at the hardware level. Until recently these advanced graphic cards used to be very expensive and only available for SGI stations and other UNIX workstations. Things are changing rapidly and thanks to Silicon Graphics' generous licenses and driver development kit we are going to see more and more OpenGL hardware for PC users. Linux users can enjoy this opportunity, Yes! A company named 3Dfx Interactive provides a series of 3D graphics cards and support for the Linux OS through their Glide library. There is another article in this series by Phillip Ross (3Dfx Graphics Cards) that describes in detail the 3Dfx cards available to us. This shows a change of attitude by some hardware manufacturers which finally realize that the Linux market is here to stay. Linux fans should support and encourage this type of initiative.

To achieve OpenGL's hardware independence, commands for windowing tasks as well as commands for obtaining user input were excluded. This sounds like it would be a serious drawback to using OpenGL, but as we will see later (See the GLUT Programming series), it is possible to combine OpenGL with other flexible programming libraries that will handle windowing tasks and obtain user input. Furthermore, OpenGL does not provide any commands for describing complex models (molecules, airplanes, houses, birds, etc.). In OpenGL you will find only the most primitive geometric objects (points, lines, and polygons). The developer has to construct his/her own models based on these few simple primitives. There are OpenGL-related libraries that provide more complex models, and any user can use these libraries to build their own.

In our series of articles about OpenGL programming we will use the C interface for OpenGL because this is the most popular. However the reader should be aware that there are bindings available in other languages: FORTRAN, C++, Ada and Java. Later in our series, after the reader is familiar with the C interface for OpenGL we will say something about Open-Inventor, a C++ library extension to OpenGL.

Without going into too much detail, the following describes some of the features OpenGL implements:

Geometric Primitives Allow you to construct mathematical descriptions of objects. The current primitives are: points, lines, polygons, images and bitmaps.
Color coding in RGBA (Red-Green-Blue-Alpha) or in color index mode.
Viewing and Modeling permits arranging objects in a 3-dimensional scene, move our camera around space and select the desired vantage point for viewing the scene to be rendered.
Texture mapping helps to bring realism into our models by rendering images of realistic looking surfaces on to the faces of the polygon in our model.
Materials lighting is an indispensable part of all 3D graphics. OpenGL provides commands to compute the color of any point given the properties of the material and the sources of light in the room.
Double buffering helps to eliminate flickering from animations. Each successive frame in an animation is built in a separate memory buffer and displayed only when rendering of the frame is complete.
Anti-aliasing reduces jagged edges in lines drawn on a computer display. Jagged lines often appear when lines are drawn at low resolution. Anti-aliasing is a common computer graphics technique that modifies the color and intensity of the pixels near the line in order to reduce the artificial zig-zag.
Gouraud shading is a technique used to apply smooth shading to a 3D object and provide subtle color differences across its surfaces.
Z-buffering keeps track of the Z coordinate of a 3D object. The Z-buffer is used to keep track of the proximity of the viewer's object. It is also crucial for hidden surface removal.
Atmospheric Effects like fog, smoke and haze make images rendered by computer more realistic. Without atmospheric effects images appear sometimes unrealistically sharp and well defined. Fog is a term that really describes an algorithm that simulates haze, mist, smoke, pollution or simply the effect of air, adding depth to the image.
Alpha blending uses the Alpha value (diffuse-material value) of the RGBA code, allowing one to combine the color of the fragment being processed with that of the pixel already stored in the frame buffer. Imagine, for example, drawing a transparent light blue window in front of a red box. Alpha blending allows simulating the transparency of the window object so the box seen through the glass will appear with a magenta tone.
Stencil Planes restrict the drawing to certain portions of the screen.
Display lists permit storage of drawing commands in a list for later rendering. When properly used, display lists can greatly enhance rendering performance.
Polynomial Evaluators serve to support non-uniform rational B-splines. This is to help draw smooth curves through a few reference points, saving the need to store numerous points in between.
Feedback, Selection and Picking features let you create applications that allow the user to select a region of the screen or pick an object drawn on the screen. The feedback mode permits the developer to obtain the results of rendering calculations.
Raster primitives (bitmaps and pixel rectangles)
Pixel Operations
Transformations: rotation, scaling, translations, perspectives in 3D, etc.
As we mentioned, to make OpenGL truly portable and platform independent it was necessary to sacrifice all the commands that interface with the windowing system; for example: opening a window, closing a window, scaling a window, reshaping a window, reading the cursor position; and also with input devices as reading keyboard input etc.. All these actions are highly operating system dependent. Originally the GL-library had its own set of commands for window and peripheral handling but those were IRIX specific (SGI's UNIX operating system). It is up to the developer of OpenGL to know their own platform and take care of handling windows with the native platform.

Thanks to Mark J. Kilgard from SGI, there is an additional library that works around this problem. Mark wrote the GLUT-library, a GL utility toolkit library that substitutes the old AUX library (never mind what the AUX library was, forget about it!). The GLUT library is freely available. Like OpenGL, you can find the source code for GLUT as well as binary versions for Linux. The GLUT library is platform dependent, and it offers a common paradigm for the windowing and peripheral devices. Therefore, when an OpenGL application wishes to open a window for a graphics animation, it uses the GLUT command set and this takes care of the underlying windowing system. In a sense, GLUT hides from the developer the dirty details of the specific windowing systems (X11, windose, Motif, etc..) and lets one concentrate on the task at hand - the OpenGL code. Another nice advantage of using GLUT is that it makes your code platform independent. I have personally written protein and gel simulations that use GLUT and OpenGL and I have been been able to compile and run then without a problem nor a single line of machine dependent code in Linux-Intel, Linux-Alpha, or Windows 95. (I confess I do use windows 95 from time to time ;-) I strongly recommend everyone interested in writing OpenGL applications to use GLUT as your windowing handler.

Clearly knowing how to use GLUT is as important as learning OpenGL so in the current LinuxFocus series about OpenGL we will also include a number of articles that explain, step-by-step, how to use GLUT and handle peripheral devices comfortably.

In closing this short introduction, we cannot forget to mention another of the "Masters of the Universe," Brian Paul, who is steadily and patiently implementing an OpenGL-like library for Linux named Mesa. At the moment Mesa only does software rendering, meaning that it is up to the CPU to perform all the rendering tasks that might otherwise be delegated to 3D hardware, but Mesa contains hooks that are implemented internally that allows drivers for accelerated hardware to be written and utilized. Currently, drivers only exist for Mondello, S3 Virge (Win95 only), GLINT, and Voodoo 3Dfx chipsets. Thanks to the Voodoo driver (written by David Bucciarelli) Mesa can reach the same performance levels as expensive SGI stations, so if you are interested in high performance 3D-accelerated graphics go and buy a 3Dfx card.

Finally, I cannot help telling you about a personal experience on my Alpha-PC (21164 550MHz 164MRam Linux 2.0.32). I use the Mesa library for a Gel simulation program I am writing. There is no hardware support in my system for the Mesa library because up to this moment the Glide library has not been released for the Alpha system (PLEASE HURRY!!!!). Well, when Phil Ross and I recently compared the performance of his Pentium PC + 3Dfx and my Alpha PC + Matrox Millennium card we were a bit surprised to see that my gel animation run as smoothly on my own PC as on his. The OpenGL demos run even better on my system (of course, those that did not use textures). In other words, the lack of hardware support for the OpenGL calls was compensated for by the brute force of the Alpha CPU. To give you an idea of the work in each of the frames of the gel animation, every frame contained a Gel structure modeled with tens of thousands of spheres and cylinders plus all the lighting computations on it. On the PC we couldn't really see a gel with that many monomers because the computations prove to be too much for the poor Intel CPU... the Alpha on the other hand, no problem!. I can't wait to see my Alpha PC with a 3Dfx card and hardware support for Mesa.
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Source : www.linuxfocus.org

problemswithvaio · Sep 5, 2005

I actually got less lag on my old computer with cs on d3d... I was running on 512 mb and a 3dfx voodoo4 memory card, but also the drivers were from when the card first came out so I'm not too sure.

Adrynalyne · Sep 5, 2005

ACE 256 said:

you have both ....newer games tend to run better in D3D...will older games run better in openGL .....openGL and D3D are included in windows ( thow thare are older versions...)
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Actually, Windows 2000 did not contain any OpenGL support. I am unsure if Windows XP followed suit. Probably. Not that it matters, nobody uses in box video drivers anyway

Anon-068c403e2d · Sep 5, 2005

AFAIK Opengl is suported in all windows os from 95-xp.Only lack of the latest graphic card drivers can cause trouble.Many default screensavers in windows are opengl.Windows 2000 ddk did have opengl support so why do you say it was not suported adrynalyne.This kb article explains a problem with opengl on 2k http://support.microsoft.com/default.aspx?scid=kb;en-us;313377

Anon-068c403e2d · Sep 5, 2005

A list of opengl games for windows

Adrynalyne · Sep 5, 2005

kadavill said:

Windows 2000 ddk did have opengl support so why do you say it was not suported adrynalyne.
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So which Windows 2000 screensaver used OpenGL?

--I can't think of any off the top of my head.

GLsetup, a free utility, is available. According to the GLsetup Web page, it "detects a user's 3D graphics hardware and installs the correct device drivers." Windows 2000 device drivers might not be supported. You can get it from http://www.glsetup.com
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http://www.opengl.org/resources/faq/technical/mswindows.htm

Know why?

Because out of the box, Windows 2000 had no OGL drivers.

Check the ATI FAQ, it was the same thing.

http://www.ati.com/products/faqs/windows2000faq.html

OpenGL support was pulled from the Win2k beta some months back, prompting a series of problem reports from testers who found OpenGL apps were running slow and/or not working properly. The responses from Microsoft staff do not entirely make the actual position clear. One suggests that drivers for a particularly graphics card were pulled because of source code issues, while another says that "we are not supporting OGL until Direct3D is 100 per cent." Which of course suggests that Microsoft support for OpenGL would crack on ahead once Win2k went gold. A later response clarifies matters further: "No driver that ships with Win2k will contain OGL support... vendors will have to supply their own post ship." All of this however fails to make clear the extent of Microsoft's abandonment of OpenGL and the Fahrenheit project with SGI. But in an email sent two weeks ago, Microsoft's Philip Taylor (senior in MS Direct3D) states the position succinctly: "Do not let your personal preference for the Quake family of games dominate your understanding of this market. OGL is not strategic for us... as the last three years of history in the multimedia space have shown... SoftImage has about 20,000 seats total. And I just about had them convinced to do a port to D3D before we sold them. Outside of the Quake family of games there are, maybe, two hands-full of apps that use OGL. Somewhere between 5-10 per cent. D3D has overwhelming support in terms of titles, yet we have a serious lack of drivers. D3D drivers are strategic for us."
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http://www.hardwarecentral.com/hardwarecentral/news/1284/1/

Now, to say there is no open support for OGL now for Windows 2000, would be incorrect. But when it was released, it was 150% true.

Maybe you misunderstood, and did not realize the OGL is a function of the video driver, and I was referring to the in box drivers. If you don't have OGL, its simple, you update your video driver....

Adrynalyne · Sep 5, 2005

Adrynalyne said:

Actually, Windows 2000 did not contain any OpenGL support. I am unsure if Windows XP followed suit. Probably. Not that it matters, nobody uses in box video drivers anyway
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Note the bold words. They are past tense.

Anon-068c403e2d · Sep 5, 2005

Windows 2000 had no OGL drivers.
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Windows 2000 device drivers might not be supported
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Opengl:the renderer (software-with or without hardware acceleration) is different from a device driver that supports opengl.And it is the graphic card manufacturer who makes their drivers.Windows does have drivers for most of the common devices, but it is not microsofts concern really.Opengl itself was supported.If they really said no(may happen with vista).It would have raised a lot of concern manyplaces.

Opengl screensaver in xp are the ones begining with 3D ie.3dtext,3d pipe,3d flowerbox etc.Not sure about 2k.

Adrynalyne · Sep 5, 2005

kadavill said:

If they really said no(may happen with vista).It would have raised a lot of concern manyplaces.

Opengl screensaver in xp are the ones begining with 3D ie.3dtext,3d pipe,3d flowerbox etc.Not sure about 2k.
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It did!

Many of the sources have fallen off Google's radar seeing how this happened back in 99.

Believe what you like, at any rate. *shrug*

Opengl screensaver in xp are the ones begining with 3D ie.3dtext,3d pipe,3d flowerbox etc.Not sure about 2k.
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I must have a messed up Windows XP, because I have none of those screensavers.

Anon-068c403e2d · Sep 5, 2005

Another type of alarm was created during that time when quake used a modified version of opengl (mingl) and 3dfx voodoo3 failed with 2k.Could it be that you are talking of?

Adrynalyne · Sep 5, 2005

Adrynalyne said:

I must have a messed up Windows XP, because I have none of those screensavers.
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Nope! I am just blind.

Adrynalyne · Sep 5, 2005

kadavill said:

Another type of alarm was created during that time when quake used a modified version of opengl (mingl) and 3dfx voodoo3 failed with 2k.Could it be that you are talking of?
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No...

sleepygamer213 · Sep 5, 2005

Thats what I was looking for. Although i am enjoying Adrynalyne and kadavill little quarrel about OpenGL

theven 4 · Sep 5, 2005

Adrynalyne said:

Now, to say there is no open support for OGL now for Windows 2000, would be incorrect. But when it was released, it was 150% true.
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You sound like wal-mart "200% satisfaction guaranteed"

Anon-068c403e2d · Sep 6, 2005

I have been searching google groups to get information on windows 2000 support for opengl and this is what I learned

opengl32.dll was included in windows 2000(opengl v1.1)

DDK had opengl 1.1 support.1.2 came in a future release

Independent Hardware Vendors will be responsible for providing ICD's (No drivers from microsoft)

Rumours were flying as beta testers found opengl games slow.(obviously they had no driver with ogl support)

Phil Taylor response was:Microsoft will support opengl but made it clear directx was first priority.

No service pack ever added opengl to windows 2000 though bug fixes were provided.Microsoft never changed its stance it was the IHV's who provided the drivers.

Opengl architecture is a server-client architecture the opengl32.dll being the client and the hardware specific icd's which is to be provided with the driver being the client.Windows 2000 ddk included icd kits for IHV's.

Back to the future
In windows vista ms plans to make ogl run under dx.Console apps will not run ogl but game in full screen will work as in xp.Here is a power point presentation of graphic architecture under vista.

Adrynalyne: The screensavers mentioned by me are not opengl.I was misguided by a couple of sites who were misguided by the fact that the same screensaver exist for nt and were opengl but microsoft made them to directx in later os.I found this using filemon.The screensaver was accesing the dx dll.Anyway Opengl.dll the only file that microsoft makes for opengl was included in the very first release of win2k 150%
http://support.microsoft.com/dllhelp/default.aspx?l=55&fid=72590

Adrynalyne · Sep 6, 2005

But see, you proved my point right here:

Independent Hardware Vendors will be responsible for providing ICD's (No drivers from microsoft)
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Rumours were flying as beta testers found opengl games slow.(obviously they had no driver with ogl support)
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Adrynalyne said:

Not that it matters, nobody uses in box video drivers anyway
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Look at my original post. Look closely. I was talking about hardware ogl support, hence the "nobody uses in box drivers anyway". Sorry I wasnt more specific, but when I posted in a gaming forum, I figured nobody else was talking about any software rendering either.

I mean, its kind of like talking about direct draw. In this day and age, nobody uses it, except for old games.

Adrynalyne · Sep 6, 2005

By the way, you sure that isn't a beta file?

http://support.microsoft.com/dllhelp/default.aspx?l=55&fid=72590

Final rtm build of 2k was 2195, not 2160.

Anyone have Windows 2000 installed to confirm?

Anon-068c403e2d · Sep 6, 2005

nobody uses in box drivers anyway
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When I said software renderer I meant opengl/directx it doesnt mean you shouldnt use a driver.Without a driver even directx games wont run hardware acceleration.The reason why there was an alarm was because developers(of drivers) had some extra work to do.But really opengl programming is easier.Only microsoft was doing the job for directx(to promote it).From a user point of view opengl worked from day 1.

sleepygamer213 · Sep 6, 2005

XP IS based off of 2k... and XP supperts openGL....

Anon-068c403e2d · Sep 6, 2005

kadavill said:

But really opengl programming is easier.
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My mistake to use this while describing driver development.The above is true for game programming not driver development.

Anon-068c403e2d · Sep 6, 2005

http://en.wikipedia.org/wiki/Direct3D_vs._OpenGL

Note these:
1.Opengl uses extensions that means a device can add own functionality such as blend modes, new ways of transferring data to the GPU, or different texture wrapping parameters.This is probably why microsoft couldnt provide complete support without vendor drivers.
2.API speed has become insignficant in modern times.
3.Direct3d is closer to the hardware than opengl.And games perform better in directx.But opengl is more precise and used by professionals.
4.

Microsoft had two driver models for OpenGL, the Installable Client Driver which required a full ground up implementation of OpenGL by the maker of the graphics card and the Mini Client Driver where Microsoft supplied a lot of the front end transformation and setup that fed the graphics card. Microsoft abandoned the MCD driver model just before several hardware makers were ready to ship MCD drivers, which delayed full OpenGL support on Microsoft Windows.
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The above quote is what confuses Adrynalyne.MCD was abandoned in windows 2000.

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