Additional resources from the Raylib repo.

Examples/resources/shaders/glsl330/normalmap.fs

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+#version 330
+
+// Input vertex attributes (from vertex shader)
+in vec3 fragPosition;
+in vec2 fragTexCoord;
+in vec3 fragNormal; //used for when normal mapping is toggled off
+in vec4 fragColor;
+
+// Input uniform values
+uniform sampler2D texture0;
+uniform sampler2D normalMap;
+uniform vec4 colDiffuse;
+
+uniform vec3 viewPos;
+uniform vec4 tintColor;
+
+uniform vec3 lightPos;
+uniform bool useNormalMap;
+uniform float specularExponent;
+
+// Output fragment color
+out vec4 finalColor;
+
+in mat3 TBN;
+
+void main()
+{
+    vec4 texelColor = texture(texture0, vec2(fragTexCoord.x, fragTexCoord.y));
+    vec3 specular = vec3(0.0);
+    vec3 viewDir = normalize(viewPos - fragPosition);
+    vec3 lightDir = normalize(lightPos - fragPosition);
+
+    vec3 normal;
+    if (useNormalMap)
+    {
+        normal = texture(normalMap, vec2(fragTexCoord.x, fragTexCoord.y)).rgb;
+
+        //Transform normal values to the range -1.0 ... 1.0
+        normal = normalize(normal*2.0 - 1.0);
+
+        //Transform the normal from tangent-space to world-space for lighting calculation
+        normal = normalize(normal*TBN);
+    }
+    else
+    {
+        normal = normalize(fragNormal);
+    }
+
+    vec4 tint = colDiffuse*fragColor;
+
+    vec3 lightColor = vec3(1.0, 1.0, 1.0);
+    float NdotL = max(dot(normal, lightDir), 0.0);
+    vec3 lightDot = lightColor*NdotL;
+
+    float specCo = 0.0;
+
+    if (NdotL > 0.0) specCo = pow(max(0.0, dot(viewDir, reflect(-lightDir, normal))), specularExponent);
+
+    specular += specCo;
+
+    finalColor = (texelColor*((tint + vec4(specular, 1.0))*vec4(lightDot, 1.0)));
+    finalColor += texelColor*(vec4(1.0, 1.0, 1.0, 1.0)/40.0)*tint;
+
+    // Gamma correction
+    finalColor = pow(finalColor, vec4(1.0/2.2));
+    //finalColor = vec4(normal, 1.0);
+}