pixel fog in shader code (DirectX 9)

akira32

I use the pixel fog in fixed pipeline and the result is correct.(the code as below)

1. 
   
2.                 // Enable fog blending.
   
3.                 m_pD3DDevice->SetRenderState(D3DRS_FOGENABLE, TRUE);
   
4. 
   
5.                 // Set the fog color.
   
6.                 m_pD3DDevice->SetRenderState(D3DRS_FOGCOLOR, pFog->GetColor());
   
7. 
   
8.                 m_pD3DDevice->SetRenderState(D3DRS_FOGTABLEMODE, (DWORD)pFog->GetMode());
   
9. 
   
10.                 float fStart=(float)pFog->GetStart();
    
11.                 float fEnd=(float)pFog->GetEnd();
    
12.                 float fDensity=(float)pFog->GetDensity();
    
13. 
    
14.                 // Set fog parameters.
    
15.                 if( pFog->GetMode() == ENUM_FOG_MODE_LINEAR )
    
16.                 {
    
17.                         m_pD3DDevice->SetRenderState(D3DRS_FOGSTART, *(DWORD *)(&fStart));
    
18.                         m_pD3DDevice->SetRenderState(D3DRS_FOGEND,   *(DWORD *)(&fEnd));
    
19.                 }
    
20.                 else
    
21.                 {
    
22.                         m_pD3DDevice->SetRenderState(D3DRS_FOGDENSITY, *(DWORD *)(&fDensity));
    
23.                 }
    

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But when I apply the pixel fog code into a model with shader(partial submeshes have effect instance), the result is incorrect. So I render the model with shader(include the submeshes without effect instance, I use a default effect file to render them). I define the effect state(pixel fog) into the technique as below:

1. 
   
2. technique tech01
   
3. {
   
4.     pass pass01
   
5.     {
   
6.         VertexShader=compile vs_2_0 VS();
   
7. 
   
8.         FogEnable=true;
   
9.         FogTableMode=UIConst_FogType;//int
   
10.         FogStart=UIConst_FogStart;//float
    
11.         FogEnd=UIConst_FogEnd;//float
    
12.         FogDensity=UIConst_FogDensity;//float
    
13.         FogColor=0xFF0000FF;
    
14. 
    
15.         PixelShader=compile ps_3_0 PS();
    
16.     }
    
17. }
    

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But the result still the same with the previous result only using fixed pipeline.
How do I define the effect state to get the correct result of pixel fog?
or I must use the vertex and pixel shader to calculate each pixel with fog?