Unify shaders

resources/shader.fragment

@@ -1,11 +1,17 @@
-#version 460 core
-
-in vec2 fragmentTextureCoordinates;
-
-uniform sampler2D sampler;
-
-out vec4 color;
-
-void main() {
-    color = texture(sampler, fragmentTextureCoordinates);
-}
+#version 460 core
+
+in vec3 fNormal;
+in vec2 fTextureCoordinates;
+in vec3 fColor;
+
+layout(location = 3) uniform sampler2D sampler;
+
+out vec4 color;
+
+const vec3 lightDirection = normalize(vec3(0.0f, 0.0f, -1.0f));
+
+void main() {
+    vec3 sampleColor = texture(sampler, fTextureCoordinates).rgb;
+    float intensity = clamp(dot(lightDirection, -normalize(fNormal)), 0.0f, 1.0f);
+    color = vec4(intensity * sampleColor * fColor + vec3(0.15f, 0.15f, 0.15f), 1.0f);
+}