Move light around the scene

shaders/frag.glsl

@@ -1,10 +1,27 @@
 #version 330 core
 
+in vec3 vert_normal;
+in vec3 frag_position;
+
 out vec4 color;
 
+uniform vec3 camera_position;
 uniform vec3 object_color;
 uniform vec3 light_color;
+uniform vec3 light_position;
 
 void main() {
-  color = vec4(object_color * light_color, 1.0);
+  float ambient_strength   = 0.15;
+  float specular_strength  = 0.5;
+  vec3  normal             = normalize(vert_normal);
+  vec3  light_direction    = normalize(light_position - frag_position);
+  vec3  view_direction     = normalize(camera_position - frag_position);
+  vec3  reflect_direction  = reflect(-light_direction, normal);
+  float diff               = max(dot(normal, light_direction), 0.0);
+  float spec               = pow(max(dot(reflect_direction, view_direction), 0.0), 32);
+  vec3  ambient            = light_color * ambient_strength;
+  vec3  diffuse            = diff * light_color;
+  vec3  specular           = specular_strength * spec * light_color;
+
+  color = vec4(object_color * (ambient + diffuse + specular), 1.0);
 };

shaders/vert.glsl

@@ -1,11 +1,18 @@
 #version 330 core
 
 layout(location=0) in vec3 position;
+layout(location=1) in vec3 normal;
 
+out vec3 vert_normal;
+out vec3 frag_position;
+
+uniform mat3 normal_mat;
 uniform mat4 model;
 uniform mat4 view;
 uniform mat4 projection;
 
 void main() {
-  gl_Position = projection * view * model * vec4(position, 1.0);
+  vert_normal   = normal_mat * normal;
+  frag_position = vec3(model * vec4(position, 1.0));
+  gl_Position   = projection * view * model * vec4(position, 1.0);
 };