Use Tangents for correct normal calculation

The normal maps are looking good now!

Shaders/default-fragment.fs

@@ -5,6 +5,7 @@ in mediump vec2 TexCoord;
 in mediump vec3 Normal;
 in mediump vec3 FragPos;
 in mediump vec4 FragPosLightSpace;
+in mediump mat3 TBN;
 
 layout(binding=0) uniform sampler2D shadowMap;
 layout(binding=1) uniform sampler2D tex;
@@ -46,8 +47,7 @@ void main()
 
     // Get normal from normal map in the range [-1,1]
     mediump vec3 map_normal = normalize(texture(normalmap, TexCoord).rgb * 2.0 - 1.0);
-
+    mediump vec3 final_normal = normalize(TBN * map_normal);
-    mediump vec3 final_normal = map_normal;
 
     // Alpha Scissors
     if(texColor.a < 0.1)

Shaders/default-vertex.vs

@@ -9,6 +9,7 @@ out vec2 TexCoord;
 out vec3 Normal;
 out vec3 FragPos;
 out vec4 FragPosLightSpace;
+out mat3 TBN;
 
 uniform mat4 model;
 uniform mat4 view;
@@ -22,4 +23,9 @@ void main()
     Normal = NORMAL;
     FragPos = vec3(model * vec4(aPos, 1.0));
     FragPosLightSpace = lightSpaceMatrix * vec4(FragPos, 1.0);
+
+    vec3 T = normalize(vec3(model * vec4(TANGENT,   0.0)));
+    vec3 B = normalize(vec3(model * vec4(BITANGENT, 0.0)));
+    vec3 N = normalize(vec3(model * vec4(NORMAL,    0.0)));
+    TBN = mat3(T, B, N);
 }