How can I compile SM 3.0 effects in D3D11 in SlimDX?

Question

var bytecode = ShaderBytecode.CompileFromFile("shaders\\testShader.fx", "fx_5_0", ShaderFlags.None, SlimDX.D3DCompiler.EffectFlags.None, null, null, out str);
var effect = new SlimDX.Direct3D11.Effect(gpu.Device, bytecode);

This works fine but if I try to use another shader model like 4.0 or 3.0 it throws an error on the new effect creation:

E_FAIL: An undetermined error occurred (-2147467259)

How do I compile older shaders? And I've read about device context but I can't find any information on how to use them to maintain DX9 compatibility.

Answer 1

"fx_5_0" refers to the effect file version, not the shader profile. Basically it's just telling the HLSL / effect compiler which version of syntax to allow.

You actually control which shader profiles are used when you use the CompileShader function inside your techniques in the effect, like so:

technique11 RenderSceneWithTexture1Light
{
    pass P0
    {
        SetVertexShader( CompileShader( vs_4_0_level_9_3, RenderSceneVS( 1, true, true ) ) );
        SetGeometryShader( NULL );
        SetPixelShader( CompileShader( ps_4_0_level_9_3, RenderScenePS( true ) ) );
    }
}

That extra "_level_9_3" at the end specifies that you're making use of the 10level9 functionality. You can see what each feature level supports here.

Unfortunately, there is no feature level that corresponds to SM 3.0 hardware. Your options are to stick with SM 2.x support in feature level 9_3 or to jump up to full D3D10-era SM 4.0.