Normal Mapping issue

Question

The first image shows a spotlight shining correctly on the floor. The second image shows the same spotlight but rotated 180 degrees.

The first is correct, the second is not.

The third image shows the light "half if and half out"

Can anyone understand what is happening here?

Normal mapping code:

Shader.fs

vec3 CalcBumpedNormal()
{
vec3 Normal = normalize(normal0);
vec3 Tangent = normalize(tangent0);
Tangent = normalize(Tangent - dot(Tangent, Normal) * Normal);
vec3 Bitangent = cross(Tangent, Normal);
mat3 TBN = mat3(Tangent, Bitangent, Normal);

return normalize(TBN * (255.0/128.0 * texture2D(normalMap, texCoord0.xy).xyz - 1 ));
}

The model is Sponza by crytek. Loaded using Assimp Model Loader.

Answer 1

The sponza model from crytek loads bump map from an .mtl file where I found the "bump" map for the flooring..

map_bump textures\spnza_bricks_a_diff.tga bump textures\spnza_bricks_a_diff.tga

If you take a look at these textures, they are clearly not normal / bump maps, and as the image name suggests; they are diffuse textures.

If you swap the two names with the corresponding normal texture that is supplied "spnza_bricks_a_ddn.tga" then the normals work correctly.

Thanks