SL-13768 de-obfuscate the ALM version of skyF.glsl

1 files changed, 40 insertions, 62 deletions

diff --git a/indra/newview/app_settings/shaders/class2/deferred/skyF.glsl b/indra/newview/app_settings/shaders/class2/deferred/skyF.glsl
index 0c9892acad..b9e561c112 100644
--- a/indra/newview/app_settings/shaders/class2/deferred/skyF.glsl
+++ b/indra/newview/app_settings/shaders/class2/deferred/skyF.glsl
@@ -92,110 +92,88 @@ void main()
 {
 
     // World / view / projection
-    // Get relative position
-    vec3 P = pos.xyz - camPosLocal.xyz + vec3(0,50,0);
-
-    // Set altitude
-    if (P.y > 0.)
-    {
-        P *= (max_y / P.y);
-    }
-    else
-    {
-        P *= (-32000. / P.y);
-    }
-
-    // Can normalize then
-    vec3 Pn = normalize(P);
-    float  Plen = length(P);
+    // Get relative position (offset why?)
+    vec3 rel_pos = pos.xyz - camPosLocal.xyz + vec3(0,50,0);
 
-    // Initialize temp variables
-    vec4 temp1 = vec4(0.);
-    vec4 temp2 = vec4(0.);
-    vec4 blue_weight;
-    vec4 haze_weight;
-    vec4 sunlight = (sun_up_factor == 1) ? sunlight_color : moonlight_color;
-    vec4 light_atten;
+    // Adj position vector to clamp altitude
+    if (rel_pos.y > 0.) { rel_pos *= (max_y / rel_pos.y); }
+    if (rel_pos.y < 0.) { rel_pos *= (-32000. / rel_pos.y); }
+
+    // Normalized
+    vec3 rel_pos_norm = normalize(rel_pos);
+    float  rel_pos_len = length(rel_pos);
 
-    float dens_mul = density_multiplier;
+    // Initialize temp variables
+    vec4  sunlight = (sun_up_factor == 1) ? sunlight_color : moonlight_color;
 
     // Sunlight attenuation effect (hue and brightness) due to atmosphere
     // this is used later for sunlight modulation at various altitudes
-    light_atten = (blue_density + vec4(haze_density * 0.25)) * (dens_mul * max_y);
+    vec4 light_atten = (blue_density + vec4(haze_density * 0.25)) * (density_multiplier * max_y);
 
     // Calculate relative weights
-    temp1 = abs(blue_density) + vec4(abs(haze_density));
-    blue_weight = blue_density / temp1;
-    haze_weight = haze_density / temp1;
+    vec4 combined_haze = abs(blue_density) + vec4(abs(haze_density));
+    vec4 blue_weight = blue_density / combined_haze;
+    vec4 haze_weight = haze_density / combined_haze;
 
-    // Compute sunlight from P & lightnorm (for long rays like sky)
-    temp2.y = max(0., max(0., Pn.y) * 1.0 + lightnorm.y );
-    temp2.y = 1. / temp2.y;
-    sunlight *= exp( - light_atten * temp2.y);
+    // Compute sunlight from rel_pos & lightnorm (for long rays like sky)
+    float off_axis = 1.0 / max(1e-6, max(0, rel_pos_norm.y) + lightnorm.y );
+    sunlight *= exp( - light_atten * off_axis);
 
     // Distance
-    temp2.z = Plen * dens_mul;
+    float density_dist = rel_pos_len * density_multiplier;
 
-    // Transparency (-> temp1)
-    // ATI Bugfix -- can't store temp1*temp2.z in a variable because the ati
+    // Transparency (-> combined_haze)
+    // ATI Bugfix -- can't store combined_haze*density_dist in a variable because the ati
     // compiler gets confused.
-    temp1 = exp(-temp1 * temp2.z);
+    combined_haze = exp(-combined_haze * density_dist);
 
     // Compute haze glow
-    temp2.x = dot(Pn, lightnorm.xyz);
-    temp2.x = 1. - temp2.x;
-        // temp2.x is 0 at the sun and increases away from sun
-    temp2.x = max(temp2.x, .001);   
+    float haze_glow = dot(rel_pos_norm, lightnorm.xyz);
+    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)
-    temp2.x *= glow.x;
+    haze_glow *= glow.x;
         // Higher glow.x gives dimmer glow (because next step is 1 / "angle")
-    temp2.x = pow(temp2.x, glow.z);
+    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"
     // For sun, add to glow.  For moon, remove glow entirely. SL-13768
-    temp2.x = (sun_moon_glow_factor < 1.0) ? 0.0 : (sun_moon_glow_factor * (temp2.x + 0.25));
+    haze_glow = (sun_moon_glow_factor < 1.0) ? 0.0 : (sun_moon_glow_factor * (haze_glow + 0.25));
 
     // Haze color above cloud
-    vec4 color = (    blue_horizon * blue_weight * (sunlight + ambient_color)
-                + (haze_horizon * haze_weight) * (sunlight * temp2.x + ambient_color)
-             ); 
+    vec4 color = blue_horizon * blue_weight * (sunlight + ambient_color)
+               + haze_horizon * haze_weight * (sunlight * haze_glow + ambient_color); 
 
     // Final atmosphere additive
-    color *= (1. - temp1);
+    color *= (1. - combined_haze);
 
     // Increase ambient when there are more clouds
-    vec4 tmpAmbient = ambient_color;
-    tmpAmbient += max(vec4(0), (1. - ambient_color)) * cloud_shadow * 0.5; 
+    // TODO 9/20: DJH what does this do?  max(0,(1-ambient)) will change the color
+    vec4 ambient = ambient_color + max(vec4(0), (1. - ambient_color)) * cloud_shadow * 0.5; 
 
     // Dim sunlight by cloud shadow percentage
     sunlight *= max(0.0, (1. - cloud_shadow));
 
     // Haze color below cloud
-    vec4 additiveColorBelowCloud = (blue_horizon * blue_weight * (sunlight + tmpAmbient)
-                + (haze_horizon * haze_weight) * (sunlight * temp2.x + tmpAmbient)
-             ); 
-
-    
+    vec4 add_below_cloud = blue_horizon * blue_weight * (sunlight + ambient)
+                         + haze_horizon * haze_weight * (sunlight * haze_glow + ambient);
     
     // Attenuate cloud color by atmosphere
-    temp1 = sqrt(temp1);    //less atmos opacity (more transparency) below clouds
+    combined_haze = sqrt(combined_haze);    //less atmos opacity (more transparency) below clouds
 
     // At horizon, blend high altitude sky color towards the darker color below the clouds
-    color += (additiveColorBelowCloud - color) * (1. - sqrt(temp1));
+    color += (add_below_cloud - color) * (1. - sqrt(combined_haze));
     
-    float optic_d = dot(Pn, lightnorm.xyz);
-
+    float optic_d = dot(rel_pos_norm, lightnorm.xyz);
     vec3 halo_22 = halo22(optic_d);
-
     color.rgb += rainbow(optic_d);
-
     color.rgb += halo_22;
-
     color.rgb *= 2.;
     color.rgb = scaleSoftClip(color.rgb);
 
-    /// Gamma correct for WL (soft clip effect).
+    // Gamma correct for WL (soft clip effect).
     frag_data[0] = vec4(color.rgb, 1.0);
     frag_data[1] = vec4(0.0,0.0,0.0,0.0);
     frag_data[2] = vec4(0.0,0.0,0.0,1.0); //1.0 in norm.w masks off fog