SL-18190 WIP - Linear space atmospherics take 2

2 files changed, 94 insertions, 4 deletions

diff --git a/indra/newview/app_settings/shaders/class2/windlight/atmosphericsF.glsl b/indra/newview/app_settings/shaders/class2/windlight/atmosphericsF.glsl
index e578f618da..20b1e3513e 100644
--- a/indra/newview/app_settings/shaders/class2/windlight/atmosphericsF.glsl
+++ b/indra/newview/app_settings/shaders/class2/windlight/atmosphericsF.glsl
@@ -52,7 +52,7 @@ vec3 atmosFragLightingLinear(vec3 light, vec3 additive, vec3 atten)
     
     light *= atten.r;
     light += additive;
-    return light;
+    return light*2.0;
 }
 
 vec3 atmosLighting(vec3 light)
diff --git a/indra/newview/app_settings/shaders/class2/windlight/atmosphericsFuncs.glsl b/indra/newview/app_settings/shaders/class2/windlight/atmosphericsFuncs.glsl
index e7e1938a11..516550be1c 100644
--- a/indra/newview/app_settings/shaders/class2/windlight/atmosphericsFuncs.glsl
+++ b/indra/newview/app_settings/shaders/class2/windlight/atmosphericsFuncs.glsl
@@ -22,15 +22,24 @@
  * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
  * $/LicenseInfo$
  */
+
+vec3 srgb_to_linear(vec3 col);
+
 uniform vec4  lightnorm;
 uniform vec4  sunlight_color;
+vec3 sunlight_linear = srgb_to_linear(sunlight_color.rgb);
 uniform vec4  moonlight_color;
+vec3 moonlight_linear = srgb_to_linear(moonlight_color.rgb);
 uniform int   sun_up_factor;
 uniform vec4  ambient_color;
+vec3 ambient_linear = srgb_to_linear(ambient_color.rgb);
 uniform vec4  blue_horizon;
+vec3 blue_horizon_linear = srgb_to_linear(blue_horizon.rgb);
 uniform vec4  blue_density;
+vec3 blue_density_linear = srgb_to_linear(blue_density.rgb);
 uniform float haze_horizon;
 uniform float haze_density;
+vec3 haze_density_linear = srgb_to_linear(vec3(haze_density));
 uniform float cloud_shadow;
 uniform float density_multiplier;
 uniform float distance_multiplier;
@@ -41,8 +50,6 @@ uniform mat3  ssao_effect_mat;
 uniform int   no_atmo;
 uniform float sun_moon_glow_factor;
 
-vec3 srgb_to_linear(vec3 col);
-
 float getAmbientClamp() { return 1.0f; }
 
 // return colors in sRGB space
@@ -136,13 +143,96 @@ void calcAtmosphericVars(vec3 inPositionEye, vec3 light_dir, float ambFactor, ou
     additive *= vec3(1.0 - combined_haze);
 }
 
+
+
+
 // return colors in linear space
 void calcAtmosphericVarsLinear(vec3 inPositionEye, vec3 light_dir, float ambFactor, out vec3 sunlit, out vec3 amblit, out vec3 additive,
                          out vec3 atten, bool use_ao)
 {
-    calcAtmosphericVars(inPositionEye, light_dir, ambFactor, sunlit, amblit, additive, atten, use_ao);
+#if 0
+    calcAtmosphericVars(inPositionEye, light_dir, 1.0, sunlit, amblit, additive, atten, false);
     sunlit = srgb_to_linear(sunlit)*2.25;
     amblit = srgb_to_linear(amblit)*0.15;
     additive = srgb_to_linear(additive);
     atten = srgb_to_linear(atten);
+#else
+    vec3 rel_pos = inPositionEye;
+
+    //(TERRAIN) limit altitude
+    if (abs(rel_pos.y) > max_y) rel_pos *= (max_y / rel_pos.y);
+
+    vec3  rel_pos_norm = normalize(rel_pos);
+    float rel_pos_len  = length(rel_pos);
+    vec3  sunlight     = (sun_up_factor == 1) ? sunlight_linear : moonlight_linear;
+
+    // sunlight attenuation effect (hue and brightness) due to atmosphere
+    // this is used later for sunlight modulation at various altitudes
+    vec3 light_atten = (blue_density_linear + (haze_density_linear * 0.25)) * (density_multiplier * max_y);
+    // I had thought blue_density and haze_density should have equal weighting,
+    // but attenuation due to haze_density tends to seem too strong
+
+    
+    vec3 combined_haze_linear = blue_density_linear + haze_density_linear;
+    vec3 combined_haze = blue_density.rgb + vec3(haze_density);
+    vec3 blue_weight   = blue_density_linear / combined_haze_linear;
+    vec3 haze_weight   = haze_density_linear / combined_haze_linear;
+
+    //(TERRAIN) compute sunlight from lightnorm y component. Factor is roughly cosecant(sun elevation) (for short rays like terrain)
+    float above_horizon_factor = 1.0 / max(1e-6, lightnorm.y);
+    sunlight *= exp(-light_atten * above_horizon_factor);  // for sun [horizon..overhead] this maps to an exp curve [0..1]
+
+    // main atmospheric scattering line integral
+    float density_dist = rel_pos_len * density_multiplier;
+
+    // Transparency (-> combined_haze)
+    // ATI Bugfix -- can't store combined_haze*density_dist*distance_multiplier in a variable because the ati
+    // compiler gets confused.
+    combined_haze = exp(-combined_haze * density_dist * distance_multiplier);
+    combined_haze_linear = exp(-combined_haze_linear * density_dist * distance_multiplier);
+    // final atmosphere attenuation factor
+    atten = combined_haze.rgb;
+
+    // compute haze glow
+    float haze_glow = dot(rel_pos_norm, lightnorm.xyz);
+
+    // dampen sun additive contrib when not facing it...
+    // SL-13539: This "if" clause causes an "additive" white artifact at roughly 77 degreees.
+    //    if (length(light_dir) > 0.01)
+    haze_glow *= max(0.0f, dot(light_dir, rel_pos_norm));
+
+    haze_glow = 1. - haze_glow;
+    // haze_glow is 0 at the sun and increases away from sun
+    haze_glow = max(haze_glow, .001);  // set a minimum "angle" (smaller glow.y allows tighter, brighter hotspot)
+    haze_glow *= glow.x;
+    // higher glow.x gives dimmer glow (because next step is 1 / "angle")
+    haze_glow = pow(haze_glow, glow.z);
+    // glow.z should be negative, so we're doing a sort of (1 / "angle") function
+
+    // add "minimum anti-solar illumination"
+    haze_glow += .25;
+
+    haze_glow *= sun_moon_glow_factor;
+
+    vec3 amb_color = ambient_linear;
+
+    // increase ambient when there are more clouds
+    vec3 tmpAmbient = amb_color + (vec3(1.) - amb_color) * cloud_shadow * 0.5;
+
+    // Similar/Shared Algorithms:
+    //     indra\llinventory\llsettingssky.cpp                                        -- LLSettingsSky::calculateLightSettings()
+    //     indra\newview\app_settings\shaders\class1\windlight\atmosphericsFuncs.glsl -- calcAtmosphericVars()
+    // haze color
+    vec3 cs = sunlight.rgb * (1. - cloud_shadow);
+    additive = (blue_horizon_linear.rgb * blue_weight.rgb) * (cs + tmpAmbient.rgb) + (haze_horizon * haze_weight.rgb) * (cs * haze_glow + tmpAmbient.rgb);
+
+    // brightness of surface both sunlight and ambient
+    sunlit = sunlight.rgb;
+    amblit = tmpAmbient.rgb;
+    additive *= vec3(1.0 - combined_haze_linear);
+
+    sunlit *= 0.8;
+    amblit *= 0.05;
+    additive *= 0.25;
+#endif
 }