Cartoon shader help

struct VS_INPUT
{
float4 position : POSITION;
float3 normal : NORMAL;
float3 diffuse : COLOR;
float2 tex0 : TEXCOORD0;
};

struct VS_OUTPUT
{
float4 position : POSITION;
float3 diffuse : COLOR;
float2 tex0 : TEXCOORD0;
float2 tex1 : TEXCOORD1;
};

vector eyePos: register(c4);
vector lightPos: register(c5);
vector lightDir: register(c6);

VS_OUTPUT main(const VS_INPUT input,
uniform matrix matWorldViewProj : c0)
{
VS_OUTPUT output;

// Compute final worldviewproj transformation
output.position = mul(matWorldViewProj, input.position);

// Compute normalized vertex-to-eye vector in object space
vector vNormVertexToEye = normalize(eyePos - input.position);

// Do lookup into cartoon texture
output.tex0 = dot(input.normal, -lightDir);

// Do lookup into cartoon edge texture
output.tex1 = dot(input.normal, vNormVertexToEye);

// Output mesh material
output.diffuse = input.diffuse;

return output;
}