New Video Card Requires New Shaders!

[mgh 89]

In P3D Tips and Tricks forum there is a topic titled New Video Card Requires New Shaders! which has been locked after the initial post so I can't ask this question there.

 

Are new shaders required when the drivers are updated with the video card unchanged?

[N1G 88]

Gerry, you do not need to do anything with shaders on a driver change.

 

Regards

Bob

[n4gix 4,947]

Gerry, you did the right thing by asking here. The "Tips and Tricks" forum is solely for information that needs to be easily and quickly found. Discussions would simply dilute and adversely affect the raison d'etre for that forum.

 

There is an optional entry one can put into the Prepar3D.CFG file that will automatically rebuild the shaders whenever a change is made in the UI should one wish that to happen:

[GRAPHICS]
SHADER_CACHE_VERSION=1

[mgh 89]

Thanks for the explanation Bill. I'm intrigued to know why changing the hardware requires re-compilation but changing the drivers doesn't - given DirectX is supposed to isolate applications from hardware.

[n4gix 4,947]

Gerry, that is a very good question for which I honestly have no authoritative answer...

 

Presumably for the same reason shaders have been compiled for specific hardware ever since DX8.0 was developed:

 

Shaders were first added to Microsoft DirectX in DirectX 8.0. At that time, several virtual shader machines were defined, each roughly corresponding to a particular graphics processor produced by the top 3D graphics vendors.

 

http://msdn.microsoft.com/en-us/library/windows/desktop/bb509704(v=vs.85).aspx

[mgh 89]

my, possibly imperfect understanding is that DirectX 11 changed that.
 

Each video card implements a certain level of Microsoft DirectX (DX) functionality depending on the graphics processing units (GPUs) installed. In prior versions of Microsoft Direct3D, you could find out the version of Direct3D the video card implemented, and then program your application accordingly.

With Direct3D 11, a new paradigm is introduced called feature levels. A feature level is a well defined set of GPU functionality. For instance, the 9_1 feature level implements the functionality that was implemented in Microsoft Direct3D 9, which exposes the capabilities of shader models ps_2_x and vs_2_x, while the 11_0 feature level implements the functionality that was implemented in Direct3D 11.

Now when you create a device, you can attempt to create a device for the feature level that you want to request. If the device creation works, that feature level exists, if not, the hardware does not support that feature level. You can either try to recreate a device at a lower feature level or you can choose to exit the application. For more info about creating a device, see the D3D11CreateDevice function.

Using feature levels, you can develop an application for Direct3D 9, Microsoft Direct3D 10, or Direct3D 11, and then run it on 9, 10 or 11 hardware (with some exceptions of course, new 11 features will not run on an existing 9 card for example). Here is a couple of other basic properties of feature levels:

 

http://msdn.microsoft.com/en-us/library/windows/desktop/ff476876(v=vs.85).aspx