Directional Light Problems

cbuffer cb0{// Current lighting information - ambient + two point lightsfloat4 AmbientColour;float4 Light1Position;   // Point light 1 - positionfloat4 Light1Colour;     // Point light 1 - colourfloat  Light1Brightness; // Point light 1 - brightnessfloat4 Light2Position;   // light 2...float4 Light2Colour;float  Light2Brightness;// Shininess of material and camera position needed for specular calculationfloat4 CameraPosition;float SpecularPower;};// Access to texture 0Texture2D Texture; SamplerState MeshTextureSampler;//-----------------------------------------------------------------------------// Input / output structures//-----------------------------------------------------------------------------struct PS_Input{	float4 Position      : SV_Position; // New semantics for DX10 - pixel position from vertex shader - not used in DX9	float2 TexCoord0     : TEXCOORD0;	float3 WorldPosition : TEXCOORD1; // The world position of the pixel	float3 WorldNormal   : TEXCOORD2; // The world normal of the pixel};struct PS_Output{	float4 Colour : SV_Target; // New semantics for DX10 - output to render target -replaces COLOR semantic in DX9};//-----------------------------------------------------------------------------// Main function//-----------------------------------------------------------------------------void main( in PS_Input i, out PS_Output o ) {	// Renormalise world normal for the pixel as it has been interpolated from the vertex world normals & may not be length 1	float3 WorldNormal = normalize( i.WorldNormal );	// Lighting preparation	// Get normalised vector to camera for specular equation (common for all lights)	float3 CameraDir = normalize( CameraPosition - i.WorldPosition );	// Accumulate diffuse and specular colour effect from each light	float3 TotalDiffuseColour = AmbientColour;	float3 TotalSpecularColour = 0;	//Light 1 - Point Light	// Calculate diffuse lighting from the 1st light. Standard equation: Diffuse = light colour * max(0, N.L)	float3 LightDir = Light1Position - i.WorldPosition;	float LightDist = length( LightDir );	float LightStrength = saturate( Light1Brightness / LightDist );	LightDir /= LightDist;	float3 DiffuseColour = LightStrength * Light1Colour * saturate( dot( WorldNormal, LightDir ) );	TotalDiffuseColour += DiffuseColour;	// Calculate specular lighting from the 1st light. Standard equation: Specular = light colour * max(0, (N.H)^p)	// Slight tweak here: multiply by diffuse colour rather than light colour	float3 Halfway = normalize( CameraDir + LightDir );	TotalSpecularColour += DiffuseColour * saturate( pow( dot( WorldNormal, Halfway ), SpecularPower ) );	// Second light - Directional light	// Calculate diffuse lighting from the 2nd light	LightDir = Light2Position - i.WorldPosition;	LightDist = length( LightDir );	LightStrength = saturate( Light2Brightness / LightDist );	LightDir /= LightDist;	//Check if the pixel is in line of sight of the light	float diffuseFactor = dot( -LightDir, WorldNormal );	if( diffuseFactor > 0.0f )	{		DiffuseColour = LightStrength * Light2Colour * saturate( dot( WorldNormal, LightDir ) );		TotalDiffuseColour += DiffuseColour;		// Calculate specular lighting from the 2nd light		Halfway = normalize( CameraDir + LightDir );		TotalSpecularColour += DiffuseColour * saturate( pow( dot( WorldNormal, Halfway ), SpecularPower ) );	}	// Final blending	// Combine lighting colours with texture - alpha channel of texture is a specular map	float4 TextureColour = Texture.Sample( MeshTextureSampler, i.TexCoord0 );	o.Colour.rgb = TotalDiffuseColour * TextureColour.rgb + TotalSpecularColour * TextureColour.a; 	// Set alpha blending to 1 (no alpha available in texture)	o.Colour.a = 1.0f;}