Add photorealistic experimental shader

assets/voxygen/shaders/include/light.glsl

@@ -198,12 +198,15 @@ float lights_at(vec3 wpos, vec3 wnorm, vec3 /*cam_to_frag*/view_dir, vec3 mu, ve
         /* is_direct = true; */
         float computed_shadow = ShadowCalculationPoint(i, -difference, wnorm, wpos/*, light_distance*/);
         // directed_light += is_direct ? max(computed_shadow, /*LIGHT_AMBIANCE*/0.0) * direct_light : vec3(0.0);
-        // Non-physically emulate ambient light nearby
-        float ambiance = mix(0.05, 0.5, (dot(wnorm, direct_light_dir) + 1.0) * 0.5) * strength;
-        #ifdef FIGURE_SHADER
-            // Non-physical hack. Subtle, but allows lanterns to glow nicely
-            // TODO: Make lanterns use glowing cells instead
-            ambiance += 0.1 / distance_2;
+        float ambiance = 0.0;
+        #ifndef EXPERIMENTAL_PHOTOREALISTIC
+            // Non-physically emulate ambient light nearby
+            ambiance = mix(0.05, 0.5, (dot(wnorm, direct_light_dir) + 1.0) * 0.5) * strength;
+            #ifdef FIGURE_SHADER
+                // Non-physical hack. Subtle, but allows lanterns to glow nicely
+                // TODO: Make lanterns use glowing cells instead
+                ambiance += 0.1 / distance_2;
+            #endif
         #endif
         directed_light += (is_direct ? mix(LIGHT_AMBIANCE, 1.0, computed_shadow) * direct_light : vec3(0.0)) + ambiance * color;
         // directed_light += (is_direct ? 1.0 : LIGHT_AMBIANCE) * max(computed_shadow, /*LIGHT_AMBIANCE*/0.0) * direct_light;// : vec3(0.0);

assets/voxygen/shaders/include/sky.glsl

@@ -46,10 +46,7 @@ const vec3 NIGHT_LIGHT   = vec3(5.0, 0.75, 0.2);
 // Linear RGB, scattering coefficients for atmosphere at roughly R, G, B wavelengths.
 //
 // See https://en.wikipedia.org/wiki/Diffuse_sky_radiation
-//
-// The most realistic value is `vec3(0.05, 0.10, 0.23)`, but this looks bad in some cases, mostly because we don't
-// compensate for the dynamic range of the human eye vs the screen.
-const vec3 MU_SCATTER = vec3(0.15, 0.15, 0.23);
+const vec3 MU_SCATTER = vec3(0.05, 0.10, 0.23);
 
 const float SUN_COLOR_FACTOR = 5.0;//6.0;// * 1.5;//1.8;
 const float MOON_COLOR_FACTOR = 5.0;//6.0;// * 1.5;//1.8;
@@ -319,11 +316,14 @@ vec3 lightning_at(vec3 wpos) {
 // cam_attenuation is the total light attenuation due to the substance for beams between the point and the camera.
 // surface_alt is the altitude of the attenuating surface.
 float get_sun_diffuse2(DirectionalLight sun_info, DirectionalLight moon_info, vec3 norm, vec3 dir, vec3 wpos, vec3 mu, vec3 cam_attenuation, float surface_alt, vec3 k_a, vec3 k_d, vec3 k_s, float alpha, vec3 voxel_norm, float voxel_lighting, out vec3 emitted_light, out vec3 reflected_light) {
-    const float MIN_SHADOW = 0.15;
     const vec3 SUN_AMBIANCE = MU_SCATTER;//0.23;/* / 1.8*/;// 0.1 / 3.0;
-    // Boost moon ambiance, because we don't properly compensate for pupil dilation (which should occur *before* HDR,
-    // not in the end user's eye). Also, real nights are too dark to be fun.
-    const vec3 MOON_AMBIANCE = MU_SCATTER * 5;
+    #ifdef EXPERIMENTAL_PHOTOREALISTIC
+        const vec3 MOON_AMBIANCE = MU_SCATTER;
+    #else
+        // Boost moon ambiance, because we don't properly compensate for pupil dilation (which should occur *before* HDR,
+        // not in the end user's eye). Also, real nights are too dark to be fun.
+        const vec3 MOON_AMBIANCE = vec3(0.15, 0.25, 0.23) * 5;
+    #endif
 
     /* vec3 sun_dir = sun_info.dir;
     vec3 moon_dir = moon_info.dir; */

voxygen/src/render/mod.rs

@@ -522,4 +522,7 @@ pub enum ExperimentalShader {
     /// Make the UI uses nearest neighbor filtering for scaling images instead
     /// of trying to filter based on the coverage of the sampled pixels.
     UiNearestScaling,
+    /// Prefer using physically-based values for various rendering parameters,
+    /// where possible.
+    Photorealistic,
 }