c++ - Point Lighting Error Directx 11 -

i'm new directx 11, , programmed distance dependent point light shader works pretty rotated , translated objects, after tried scaling models, lighting got dimmer if scaled model larger, , lighting got brighter if scaled model smaller. thought might normals, made sure multiply them inverse transpose of world matrix, , made sure normalize them in pixel shader after interpolated. here shader code:

texture2d txdiffuse : register( t0 ); samplerstate samanisotropic {     filter = anisotropic;     maxanisotropy = 4; };  cbuffer constantbuffer : register( b0 ) {     matrix world;     matrix view;     matrix projection;     matrix worldinvtrans;     float3 lightpos;     float pad1;     float3 eyepos;     float pad2;     float3 at;     float pad3;     float shownorms; }   struct vs_input {     float4 pos : position;     float3 norm : normal;     float2 texcoor : texcoord0;  };  struct ps_input {     float4 pos : sv_position;     float3 norm : normal;     float3 lightdir : position0;     float3 eyevector : position1;     float2 texcoor : texcoord0;     float distance : float0;     float shownorms : float1;  };  ps_input vs( vs_input input ) {     ps_input output = (ps_input)0;     output.pos = mul( input.pos, world );     output.lightdir = normalize( lightpos - output.pos );     output.eyevector = normalize( eyepos - @ );     output.distance = distance( lightpos, output.pos);     output.pos = mul( output.pos, view );     output.pos = mul( output.pos, projection );     output.norm = mul( input.norm, worldinvtrans );     output.texcoor = input.texcoor;     output.shownorms = shownorms;      return output; }  float4 ps( ps_input input) : sv_target {     input.norm = normalize( input.norm );      float specterm = 0;      float3 reflvector = normalize( reflect( input.lightdir, input.norm ) );      [flatten]     if ( dot( reflvector, input.eyevector ) >= 0 )     {         specterm = pow(  dot( reflvector, input.eyevector ) , 50 );     }     float diffuseterm = saturate( dot( input.lightdir, input.norm ) );     float4 ambient = float4( 0.25f, 0.25f, 0.25f, 1.0f );     float4 lightcolor = float4( 1.0f, 1.0f, 1.0f, 1.0f );     return ( (ambient + (diffuseterm + specterm) / (pow( input.distance, 1 ) * 0.025f)) * lightcolor * txdiffuse.sample( samanisotropic, input.texcoor ) ) * ( 1 - input.shownorms ) + float4( input.norm, 1.0f ) * input.shownorms; } 

i still suspicious normals weren't correct, edited last line in pixel shader shade model based on normal vectors if shownorms = 1.0f. normals looked transformed correctly. still suspicious, replaced model plane on xz axis, , scaled 50 times. when rendered it, lighting still dim, plane green when set shownorms 1.0f, must mean normals pointing in upwards y direction. if i'm transforming normals correctly , normalizing them, causing these lighting errors?

if helps, here code when set constant buffers plane:

//render plane     mworld = xmmatrixidentity();     cb1.mworld = xmmatrixtranspose( xmmatrixmultiply( xmmatrixmultiply( mworld, xmmatrixscaling( 50.0f, 1.0f, 50.0f ) ), xmmatrixtranslation( 0.0f, -5.0f, 0.0f ) ) );     xmmatrix = cb1.mworld;     a.r[3] = xmvectorset(0.0f, 0.0f, 0.0f, 1.0f);  det = xmmatrixdeterminant(a); cb1.mworldinvtrans = xmmatrixinverse(&det, a);  g_pimmediatecontext->updatesubresource( g_pcbuffershader1, 0, null, &cb1, 0, 0 ); 

edit: changed code little bit fix specterm:

texture2d txdiffuse : register( t0 ); samplerstate samanisotropic {     filter = anisotropic;     maxanisotropy = 4; };  cbuffer constantbuffer : register( b0 ) {     matrix world;     matrix view;     matrix projection;     matrix worldinvtrans;     float3 lightpos;     float pad1;     float3 eyepos;     float pad2;     float3 at;     float pad3;     float shownorms; }   struct vs_input {     float4 pos : position;     float3 norm : normal;     float2 texcoor : texcoord0;  };  struct ps_input {     float4 pos : sv_position;     float3 norm : normal;     float3 lightdir : position0;     float3 eyevector : position1;     float2 texcoor : texcoord0;     float distance : float0;     float shownorms : float1;  };  ps_input vs( vs_input input ) {     ps_input output = (ps_input)0;     output.pos = mul( input.pos, world );     output.lightdir = lightpos - output.pos;     output.eyevector = eyepos - at;     output.distance = distance( lightpos, output.pos );     output.pos = mul( output.pos, view );     output.pos = mul( output.pos, projection );     output.norm = mul( input.norm, worldinvtrans );     output.texcoor = input.texcoor;     output.shownorms = shownorms;      return output; }  float4 ps( ps_input input) : sv_target {     input.norm = normalize( input.norm );     input.lightdir = normalize( input.lightdir );     input.eyevector = normalize( input.eyevector );      float specterm = 0;      float3 reflvector = normalize( reflect( -input.lightdir, input.norm ) );      [flatten]     if ( dot( reflvector, input.eyevector ) >= 0 )     {         specterm = pow(  dot( reflvector, input.eyevector ) , 50 );     }     float diffuseterm = saturate( dot( input.lightdir, input.norm ) );     float4 ambient = float4( 0.25f, 0.25f, 0.25f, 1.0f );     float4 lightcolor = float4( 1.0f, 1.0f, 1.0f, 1.0f );     return ( (ambient + (diffuseterm + specterm) / (pow( input.distance, 1 ) * 0.025f)) * lightcolor * txdiffuse.sample( samanisotropic, input.texcoor ) ) * ( 1 - input.shownorms ) + float4( input.norm, 1.0f ) * input.shownorms; } 

i think should try normalize lightdir vector in pixel shader well. if plane large may happen, after interpolation of these 2 vectors, vector in pixel shader not normalized. error increase scale goes up. give try. picture below shows problem.