Improve lighting

- No specular on surfaces facing away from the light source
- Transform the light direction to view space to ensure that all
  lighting calculations happen in a consistent coordinate space.
- Other lighting tweaks

assets/shaders/gl_textured.frag

@@ -6,7 +6,7 @@ in  vec3 v_position;
 
 out vec4 frag_color;
 
-uniform vec3 u_light;
+uniform vec3 u_light;      // direction TO the light (normalized)
 uniform sampler2D tex;
 uniform vec3 color;        // base colour factor (acts as solid colour when no texture)
 
@@ -14,20 +14,29 @@ void main() {
     // Combine base texture (or constant white) with colour factor supplied by CPU.
     vec3 base_col = texture(tex, v_tex).rgb * color;
 
-    vec3 ambient_color  = base_col * 0.2;
+    vec3 N = normalize(v_normal);
-    vec3 diffuse_color  = base_col * 0.6;
+    vec3 L = normalize(u_light);
-    vec3 specular_color = vec3(1.0);
 
-    // u_light is the direction **from the light towards the fragment**.
+    // Classic Blinn-Phong lighting
-    float diffuse = max(dot(normalize(v_normal), normalize(u_light)), 0.0);
+    // Ambient: always present
+    vec3 ambient = base_col * 0.15;
 
-    vec3 camera_dir = normalize(-v_position);
+    // Diffuse: N dot L, clamped
-    vec3 half_dir   = normalize(normalize(u_light) + camera_dir);
+    float NdotL = max(dot(N, L), 0.0);
-    float specular  = pow(max(dot(half_dir, normalize(v_normal)), 0.0), 16.0);
+    vec3 diffuse = base_col * NdotL * 0.7;
 
-    vec3 result = ambient_color + diffuse * diffuse_color + specular * specular_color;
+    // Specular: only on surfaces facing the light (NdotL > 0)
+    float specular = 0.0;
+    if (NdotL > 0.0) {
+        vec3 V = normalize(-v_position);         // view direction (camera at origin in view space)
+        vec3 H = normalize(L + V);               // half-vector
+        float NdotH = max(dot(N, H), 0.0);
+        specular = pow(NdotH, 32.0) * 0.5;       // tighter highlight, moderated intensity
+    }
 
-    // Convert from linear to sRGB for display (approximate γ-correction)
+    vec3 result = ambient + diffuse + vec3(specular);
+
+    // Convert from linear to sRGB for display (approximate gamma correction)
     result = pow(result, vec3(1.0 / 2.2));
 
     frag_color = vec4(result, 1.0);

glium_platform/src/render/basic.rs

@@ -59,7 +59,11 @@ impl RenderingSystem for BasicMeshRenderingSystem {
         };
 
         // Use HDR-derived environment light direction if provided, otherwise default to downward
-        let light_dir: Vec3 = if ctx.env_light_dir.length_squared() > 0.0 { ctx.env_light_dir.normalize() } else { Vec3::new(0.0, -1.0, 0.0) };
+        let light_dir_world: Vec3 = if ctx.env_light_dir.length_squared() > 0.0 { ctx.env_light_dir.normalize() } else { Vec3::new(0.0, -1.0, 0.0) };
+
+        // Transform light direction to view space (normals/positions are in view space)
+        let view_mat3 = glam::Mat3::from_mat4(cam.view());
+        let light_dir_view = (view_mat3 * light_dir_world).normalize();
 
         let asset_manager = ctx.asset_manager.borrow();
 
@@ -90,7 +94,7 @@ impl RenderingSystem for BasicMeshRenderingSystem {
                 model:      tr.matrix().to_cols_array_2d(),
                 view:       cam.view().to_cols_array_2d(),
                 projection: cam.projection().to_cols_array_2d(),
-                u_light:    [light_dir.x, light_dir.y, light_dir.z],
+                u_light:    [light_dir_view.x, light_dir_view.y, light_dir_view.z],
                 tex:        sampler,
                 color:      [c[0], c[1], c[2]],
                 uv_offset:  [mat.uv_offset.x, mat.uv_offset.y],

glium_platform/src/render/skybox.rs

@@ -119,7 +119,7 @@ impl RenderingSystem for SkyboxRenderingSystem {
 
 		// Load EXR from assets/exr
 		let manifest_dir = env!("CARGO_MANIFEST_DIR");
-		let path = std::path::Path::new(manifest_dir).join("../assets/exr/qwantani_sunset_puresky_2k.exr");
+		let path = std::path::Path::new(manifest_dir).join("../assets/exr/citrus_orchard_road_puresky_4k.exr");
 		let (equirect_srgb, light_dir) = Self::load_hdr_equirect_and_analyze(display, &path);
 		Self { program, quad_vb, quad_ib, equirect_srgb, light_dir }
 	}