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Hi,

Juhana Sadeharju wrote:
> Somebody should tell ATI that DirectX is not available in Linux.
> (Though, I have not asked my Microsoft dealer about it.)
> There is no OpenGL vs. DirectX competition in Linux.

Juhana, you are naive. What is the market share of Linux in games which
ATI is targeting? Where is Linux on game consoles (another ATI market)?

> In Windows, why they choose DirectX over OpenGL? I remember Carmack
> flamed DirectX at some point. Now he is using DirectX.
> If DirectX is truelly better, then in Linux, we should have equivalent
> system. Perhaps OpenGL could be evolved more toward DirectX, or
> an exact clone of DirectX API could be written over OpenGL. That would
> make life in Linux simpler both to the game developers and the driver
> authors.

Nonsense - that would be chasing wind because Microsoft is changing the
API all the time. Wine project is doing exactly this and they are
finally able to run some DirectX (or rather Direct3D) games. However, it
took them more than decade, threats of patent lawsuits from Microsoft
and it is still not good enough for use and probably never will be,
because they are chasing a moving target they cannot control.

> OSG, Delta3D, Crystal Space etc. compiles in multiple systems. Why
> commercial game engines do not? What are the parts of the game or
> engine which does not compile in Linux without major modifications?

Why they should? The purpose of a game engine is to run the game and
sell it for 6-9months after release. It has to run only on Windows,
sometimes Mac (extremely rare). The effort is reused max. twice for a
sequel next year with a bit of new geometry and animations or licensed
to others to make a knock-off game. Then a new engine is made for the
next hw. generation and the old code is scrapped. Why would you make
something like this portable and had to deal with the tons of problems
this brings when all that you need is support for a single platform?

It doesn't make sense economically to make the code portable unless you
plan to sell on Linux (which is not a market for games, really). How
many people would play Quake 4 or Oblivion on IRIX, for example?

Compare that with platforms like OSG which are here to stay for quite a
few years and cannot change completely every time Microsoft decides to
pull a fast one and change the APIs. Flightsim company selling
multi-million dollar systems wouldn't be happy to have to change their
software every 2 years, because it costs lot of money and you need to
support it for decades - it is not a throw-away product as a game which
you cannot find on the shelf anymore 6 months later. Thus they have only
one choice - make the code portable and use standards such as OpenGL so
that you can survive the hardware and software changes without too much
hassle.

This explains also choice of Direct3D over OpenGL - the latest features
of the hardware are exposed in Direct3D with the proprietary drivers,
not in OpenGL extensions which take years to get approved and
implemented. However, once it is there, it will stay.

> OSG is available, but what scenegraph elements it does not have
> compared to commercial games/engines? Why OSG is not that good that
> game developers must have it?

Except that OSG is not a game engine. That is not to say that you cannot
make a game with it, however you need a lot more than OSG to make a
game. Delta3D is trying to be a game engine - look for yourself how much
extra work you need to put on top of a scene graph (OSG) to make a game
engine. And it is still rather simple (no offense meant to Delta3D
guys), some commercial engines do much more.

Not to mention the add-on things you get with commercial engines - such
as an integrated content production pipeline which is much more
important than a scene graph for game development - you need to create
the geometry, models, animations and make the tools work together and
with your engine. This is hard to get and OSG doesn't really have that
(and has no real need for it, since its purpose is different).

So, please, learn something about the topic before trying to tell others
what they should do, OK?

Jan


- --

Jan Ciger
GPG public key: http://www.keyserver.net/

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