I'm new to Directx 11, and I programmed a distance dependent point light shader that works pretty well for rotated and translated objects, but after I tried scaling my models, the lighting got dimmer if I scaled the model larger, and the lighting got brighter if I scaled the model smaller. I thought it might be the normals, but I made sure to multiply them by the inverse transpose of the world matrix, and I made sure to normalize them in the pixel shader after they are interpolated. Here is the 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 - 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 );
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 was still suspicious that the normals weren't correct, so I edited the last line in my pixel shader to shade the model based on the normal vectors if showNorms = 1.0f. The normals looked like they were transformed correctly. Still suspicious, I replaced my model with a plane on the XZ axis, and scaled it up 50 times. When I rendered it, the lighting was still dim, but the plane was green when I set showNorms to 1.0f, which must mean that the normals are all pointing in the upwards Y direction. If I'm transforming my normals correctly and normalizing them, what could be causing these lighting errors?
If this helps, here is my code when I set the constant buffers for the 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 A = 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: I changed the code a little bit to fix the 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;
}
