Shader

float4x4 wvp : register( c0 );
float4x4 world : register( c5 );

#ifdef USE_LIGHTING
    float3 lightPosition : register( c10 );
    float3 lightColor : register( c11 );
    float lightRange : register( c12 );
    float3 ambientColor : register( c13 );
#endif

struct VS_INPUT {
    float4 position : POSITION;
    float2 texcoord : TEXCOORD0;
    float4 color : COLOR0;
};

struct VS_OUTPUT {
    float4 position : POSITION;
    float2 texcoord : TEXCOORD0;
    float4 color : TEXCOORD1;
};

VS_OUTPUT main( VS_INPUT input ) {
    VS_OUTPUT output;

    output.position = mul( wvp, input.position );
    output.texcoord = input.texcoord;

#ifdef USE_LIGHTING
    float4 worldPos = mul( world, input.position );
    float distance = length( worldPos - lightPosition );
    float attenuation = lightRange * 1.25f / ( 1 + distance * distance );
    output.color = float4( lightColor.xyz * input.color.xyz * attenuation + ambientColor.xyz, 1.0f )  ;
#else
    output.color = input.color;
#endif

    return output;
};