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Normal mapping dependent on view.


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#1 jajcek   Members   -  Reputation: 274

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Posted 14 September 2013 - 08:13 AM

Hi,

 

I've got a problem that normal mapping is dependent on view. It looks like this (sorry for the watermarks): http://www.youtube.com/watch?v=-V_2Pp4kiLM&feature=youtu.be

 

The normal mapping is calculated in the pixel shader as follows (it is actually taken from http://stackoverflow.com/questions/5255806/how-to-calculate-tangent-and-binormal):

 

- vertexPosition is a position in SV_POSITION semantic

- shared vertices on in the triangles

 

float3 computeNormalWithTBN(float3 vertexPosition, float2 texCoord, float3 normal ) {
    float3 p_dx = ddx(vertexPosition);
    float3 p_dy = ddy(vertexPosition);


    float2 tc_dx = ddx(texCoord);
    float2 tc_dy = ddy(texCoord);


    float3 t = normalize( tc_dy.y * p_dx - tc_dx.y * p_dy );
    float3 b = normalize( tc_dy.x * p_dx - tc_dx.x * p_dy );


    float3 n = normalize(normal);
    float3 x = cross(n, t);
    t = cross(x, n);
    t = normalize(t);


    x = cross(b, n);
    b = cross(n, x);
    b = normalize(b);


    float4 detail = normalMap.Sample( SampleType, texCoord );
    detail = (detail * 2.0f) - 1.0f;
    detail *= 6.0f;
    return normalize( normal + detail.x * t + detail.y * b );
}
// in main function
    // ...
    input.normal = computeNormalWithTBN( input.position.xyz, input.tex.xy, input.normal;
    float light = saturate( dot( input.normal, float3( 0, 0.73, -0.69 ) ) );


    float4 color = 0.3f;
    color += light;
    return color;
}
 

 

Why this happens?

 

Thanks for help.



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#2 Hodgman   Moderators   -  Reputation: 31785

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Posted 14 September 2013 - 09:24 AM

What coordinate system (aka "space") is the normal in?

In the vertex shader how do you generate the normal?

Your light direction is constant (i.e. float3( 0, 0.73, -0.69 )), so I guess it's in world-space / world-coordinates.



#3 jajcek   Members   -  Reputation: 274

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Posted 14 September 2013 - 10:05 AM

Hey, thanks for the interest.

 

I think it's in world space, but I will explain how it is calculated to not make a stupid mistake.

 

The normal is calculated on CPU and is send to the VS. To calculate normal for the "5" vertex:

1 2 3
4 5 6
7 8 9

I calculate:

XMFLOAT3 normal;
XMVECTOR v1 = {  2, height_value_of_3 - height_value_of_7, -2 };
XMVECTOR v2 = { -2, height_value_of_1 - height_value_of_9, -2 };
XMStoreFloat3( &normal, XMVector3Normalize( XMVector3Cross( v1, v2 ) ) );
return normal;

VS only passes the normals to the PS as is.






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