HLSL invalid ps_2_0 input semantic POSITION0

Question

I'm attempting to write a phong shader effect for Dx9 in RenderMonkey.

I'm getting a compile error in the pixel shader

*"invalid ps_2_0 input semantic 'POSITION0'"*

and I'm not sure how to fix it, although I know it's got to be something to do with the POSITION0 semantic in VS_OUTPUT.

I tried changing VS_OUTPUT's Pos semantic to TEXCOORD0, but then the system reports that

vertex shader must minimally write all four components of POSITION

Shaders are supplied below. Any suggestions?

Here's my vertex shader:

struct VS_INPUT 
{
   float4 Pos : POSITION0;
   float3 Normal : NORMAL0;
};

struct VS_OUTPUT 
{
   float4 Pos : POSITION0;
   float3 Normal : TEXCOORD0;
};

VS_OUTPUT vs_main( VS_INPUT Input )
{
   VS_OUTPUT Output;

   Output.Pos     = Input.Pos;
   Output.Normal  = Input.Normal;

   return Output;  
}

and my pixel shader:

    float4x4 matViewProjection;

// light source
float4 lightPos;
float4 Ambient;
float4 Diffuse;
float4 Specular;

// material reflection properties
float4 Ke;
float4 Ka;
float4 Kd;
float4 Ks;
float  nSpecular;

// eye
float4 eyePosition;

struct VS_OUTPUT 
{
   float4 Pos : POSITION0;
   float3 Normal : TEXCOORD0;
};

float4 ps_main( VS_OUTPUT vsOutput ) : COLOR0
{   
   vsOutput.Pos = mul( vsOutput.Pos, matViewProjection );


   float3 ViewDirection = normalize( eyePosition.xyz - vsOutput.Pos.xyz );
   float3 LightDirection = normalize( lightPos.xyz - vsOutput.Pos.xyz );

   float3 N = normalize( vsOutput.Normal );
   float3 R = reflect( -LightDirection, N );

   float LdotN = max( 0.0, dot( LightDirection, N ) );
   float VdotR = max( 0.0, dot( ViewDirection, R ) );

   // find colour components
   float4 a = Ka * Ambient;
   float4 d = Kd * Diffuse * LdotN;
   float4 s = Ks * Specular * pow( VdotR, nSpecular );

   float4 FragColour = Ke + a + d + s;
   return FragColour;
}

Answer 1

Okay, I found a solution for those interested.

The Vertex Shader should have the following structs defined:

struct VS_INPUT 
{
   float4 Pos : POSITION0;
   float3 Normal : NORMAL0;
};

struct VS_OUTPUT 
{
   float4 Pos : POSITION0;
   float4 PosOut : TEXCOORD0;
   float3 Normal : TEXCOORD1;
};

The VS_OUTPUT struct should be different in the pixel shader:

struct VS_OUTPUT 
{
   float4 PosOut : TEXCOORD0;
   float3 Normal : TEXCOORD1;
};

My problem stemmed from the fact that you can't have a POSITION semantic as input to the pixel shader. At least for ps_2_0.