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/**
* @file class2\windlight\atmosphericsFuncs.glsl
*
* $LicenseInfo:firstyear=2022&license=viewerlgpl$
* Second Life Viewer Source Code
* Copyright (C) 2022, Linden Research, Inc.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation;
* version 2.1 of the License only.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
* Linden Research, Inc., 945 Battery Street, San Francisco, CA 94111 USA
* $/LicenseInfo$
*/
uniform vec3 lightnorm;
uniform vec3 sunlight_color;
uniform vec3 moonlight_color;
uniform int sun_up_factor;
uniform vec3 ambient_color;
uniform vec3 blue_horizon;
uniform vec3 blue_density;
uniform float haze_horizon;
uniform float haze_density;
uniform float cloud_shadow;
uniform float density_multiplier;
uniform float distance_multiplier;
uniform float max_y;
uniform vec3 glow;
uniform float scene_light_strength;
uniform float sun_moon_glow_factor;
uniform float sky_sunlight_scale;
uniform float sky_ambient_scale;
uniform int classic_mode;
float getAmbientClamp() { return 1.0f; }
vec3 srgb_to_linear(vec3 col);
// return colors in sRGB space
void calcAtmosphericVars(vec3 inPositionEye, vec3 light_dir, float ambFactor, out vec3 sunlit, out vec3 amblit, out vec3 additive,
out vec3 atten)
{
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_color: moonlight_color;
// sunlight attenuation effect (hue and brightness) due to atmosphere
// this is used later for sunlight modulation at various altitudes
vec3 light_atten = (blue_density + vec3(haze_density * 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 = max(blue_density + vec3(haze_density), vec3(1e-6));
vec3 blue_weight = blue_density / combined_haze;
vec3 haze_weight = vec3(haze_density) / combined_haze;
//(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);
// 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 = clamp(pow(haze_glow, glow.z), -100000, 100000);
// 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_color;
// 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.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 = pow(tmpAmbient.rgb, vec3(0.9)) * 0.57;
additive *= vec3(1.0 - combined_haze);
// sanity clamp haze contribution
additive = min(additive, vec3(10));
}
vec3 srgb_to_linear(vec3 col);
// provide a touch of lighting in the opposite direction of the sun light
// so areas in shadow don't lose all detail
float ambientLighting(vec3 norm, vec3 light_dir)
{
float ambient = min(abs(dot(norm.xyz, light_dir.xyz)), 1.0);
ambient *= 0.5;
ambient *= ambient;
ambient = (1.0 - ambient);
return ambient;
}
// return lit amblit in linear space, leave sunlit and additive in sRGB space
void calcAtmosphericVarsLinear(vec3 inPositionEye, vec3 norm, vec3 light_dir, out vec3 sunlit, out vec3 amblit, out vec3 additive,
out vec3 atten)
{
calcAtmosphericVars(inPositionEye, light_dir, 1.0, sunlit, amblit, additive, atten);
amblit *= ambientLighting(norm, light_dir);
if (classic_mode < 1)
{
amblit = srgb_to_linear(amblit);
sunlit = srgb_to_linear(sunlit);
}
// multiply to get similar colors as when the "scaleSoftClip" implementation was doubling color values
// (allows for mixing of light sources other than sunlight e.g. reflection probes)
sunlit *= sky_sunlight_scale;
amblit *= sky_ambient_scale;
}
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