Whats does d3d9.dll do in the grand scheme of things

D3d9.dll is a process belonging to the Microsoft DirectX systems.  D3d9.dll allows games and multimedia tasks access DirectX 9 functionality.  DirectX is essentially a collection of multimedia API's.

Specifically, D3D9, formerly called Direct3D, is the 3D drawing API for drawing 3D graphics.  It is also the base graphics API for Xbox and Xbox 360.  Direct3D also allows applications to run fullscreen instead of windowed.

From Wikipedia: "Direct3D is a Microsoft DirectX API subsystem component. The aim of Direct3D is to abstract the communication between a graphics application and the graphics hardware drivers. It is presented like a thin abstract layer at a level comparable to GDI.  With a COM based architecture, the main difference between GDI and Direct3D is that Direct3D is directly connected to display drivers and gets better results at rendering than GDI.

Direct3D is an Immediate mode graphics API. It provides a low-level interface to every video card 3D function."

Anyway, I hope that may answer your question.

Some people says that it seems to be cuasing memory leaks in games like dragon age. I wanted to verify if that could be the case....

Yeah there's a lot to suggest it has some issues, I had hoped that directing you to MS would elicit either you have a Vista PC or that your install is not up to date because short of that I will admit I cannot help

Chris

The "memory leaks" from D3D9 come from the application itself, in the case you are speaking of, Dragon Age: Origins, the issue may be you're graphics drivers, or the video card hardware itself.

You can find updated Nvidia drivers here: http://www.nvidia.com/Download/index5.aspx?lang=en-us
Updated ATI drivers here: http://support.amd.com/us/gpudownload/Pages/index.aspx
Latest DirectX: http://www.microsoft.com/games/en-US/aboutGFW/pages/directx.aspx

i do have vista installed but would you not think that the game would use the newer dll from direct x 10 instead of the old ones from direct x 9 ..

There is a raging debate over at the game's technical forum about people being upset at the poor performcance of the game, some people are trying to analyze the game and what might be causing the issues. A typical games starts off allright but after some play time the loading time in the game gets longer and longer and a reboot usually fixes this which highly suggest a memory leak of some kind. A user was able to determine thru testing that d3d9.dll might be the culprit. Also fmodex.dll seem to be in contention and might be cuasing some problems.

DirectX 10 and 11 still use d3d9.dll, it is just the updated version of d3d9.dll that includes support for DX10 and DX11.

that is what i do not get, why would the game not use the newest dll's on your machine instead?

It is using the newest .dll, they are just still named the same.

i would assme the same but the leak seems to happen on xp and vista, i am not entirely sure for 7 though...

When you install the latest DirectX using dxwebsetup or by downloading the full redistributable of DX, you're files are updated.

I am running 7 and I also play DA:O occasionally.  I personally have not dealt with the issue, but i know of the issue.  It would seem to me that the programming in the game itself is what causes the issue from what I have read and heard.

But coult it be just one dll that would cause this entire debacle?

I suppose it's "possible"...

I highly doubt though that with all the games that are played on PC's these days that d3d9.dll is somehow broken and only this one game has the issue.  D3d9 is used quite a lot these days and I have to think that the issue is not related to that one file or we would see this issue more prevalent.