[fix] Adding support to shader 2.0b and 2.0a - LOGGED

An easy way to get a performance boost on integrated GPUs is using compiling the shaders for a lower target than the supported one. Example: a GeForce 7100 mobile supports SM3.0, but you'll get double or even triple the framerate if you drop to SM2.0 (in Basic Lighting). The problem is that most T3D shaders go over the instruction limit for SM2.0 (64 ALUs and 32 texture operations).

Everything would be fine if we could use SM2.0a or SM2.0b which all DX9c cards support and have a 512 instruction limit (enough for anything T3D does), however T3D doesn't know how to build the proper shader profile strings for those:

In gfxD3D9Shader.cpp, in GFXD3D9Shader::_init(), after this block:

String vertTarget = String::ToString("vs_%d_%d", mjVer, mnVer);
String pixTarget = String::ToString("ps_%d_%d", mjVer, mnVer);

..add this:

if (mjVer == 2 && mnVer == 1)
{      
   pixTarget  = "ps_2_a";
   vertTarget = "vs_2_0";
}
else if (mjVer == 2 && mnVer == 2)
{      
   pixTarget  = "ps_2_b";
   vertTarget = "vs_2_0";
}

This will add support for forcing the shader version to 2.1 (2.0a) and 2.2 (2.0b):

$pref::video::forcedPixVersion = 2.2; // Forces shader 2.0b
$pref::video::forcePixVersion = 1;

Now, if you T3D to be able to detect true SM2.0a SM2.0b cards, open gfxPCD3D9Device.cpp, find the method GFXPCD3D9Device::init():

After this block:

U8 *pxPtr = (U8*) &caps.PixelShaderVersion;
mPixVersion = pxPtr[1] + pxPtr[0] * 0.1;

Add this:

if (mPixVersion >= 2.0 && mPixVersion < 3.0 && caps.PS20Caps.NumTemps >= 32)
   mPixVersion += 0.2;
else if (mPixVersion >= 2.0 && mPixVersion < 3.0 && caps.PS20Caps.NumTemps >= 22)
   mPixVersion += 0.1;

The only cards which don't support shader 3.0 but support shader 2.0a are the GeForce FX line (NV30), and the only ones which support shader 2.0b are the Radeon X700 and X800 (R400). Anything else will fail to compile the shaders (example: Radeon X600, Intel 945).

All shader 3.0 and 4.0 cards (even Intel ones) support shader 2.0b and 2.0a as well.