150 lines
4.6 KiB
GLSL
150 lines
4.6 KiB
GLSL
#include "/Lib/Settings.glsl"
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#include "/Lib/Utilities.glsl"
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// MinecraftPT — Precomputed Atmosphere (analytic)
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// A compact analytic Rayleigh/Mie sky model with precomputed transmittance.
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// Provides sun/sky irradiance for the scene and sky radiance for the panorama.
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#ifndef PRECOMPUTED_ATMOSPHERE_GLSL
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#define PRECOMPUTED_ATMOSPHERE_GLSL
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// Earth-like atmosphere constants (scaled)
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const float atmosphereModel_bottom_radius = 6360.0;
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const float atmosphereModel_top_radius = 6420.0;
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const vec3 wavelengths = vec3(680.0, 550.0, 440.0); // nm
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const vec3 betaRayleigh = vec3(5.802, 13.558, 33.1) * 1e-6;
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const float betaMie = 3.996e-6;
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const float mieG = 0.8;
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vec3 RayleighPhase(float cosTheta){
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return 3.0 / (16.0 * 3.14159265) * (1.0 + cosTheta * cosTheta);
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}
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vec3 MiePhase(float cosTheta){
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float g = mieG;
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float g2 = g * g;
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return 3.0 / (8.0 * 3.14159265) * ((1.0 - g2) * (1.0 + cosTheta * cosTheta)) /
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((2.0 + g2) * pow(1.0 + g2 - 2.0 * g * cosTheta, 1.5));
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}
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// Ground intersection for ray from camera
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float GroundIntersection(vec3 pos, vec3 dir){
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float b = dot(pos, dir);
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float c = dot(pos, pos) - atmosphereModel_bottom_radius * atmosphereModel_bottom_radius;
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float h = b * b - c;
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if (h > 0.0){
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float t = -b - sqrt(h);
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if (t > 0.0) return t;
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}
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return -1.0;
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}
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float AtmosphereIntersection(vec3 pos, vec3 dir){
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float b = dot(pos, dir);
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float c = dot(pos, pos) - atmosphereModel_top_radius * atmosphereModel_top_radius;
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float h = b * b - c;
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if (h > 0.0){
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float t = -b + sqrt(h);
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if (t > 0.0) return t;
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}
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return -1.0;
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}
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// Optical depth to space (transmittance approximation)
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vec3 OpticalDepthToSpace(vec3 pos, vec3 dir){
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float tMax = AtmosphereIntersection(pos, dir);
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if (tMax < 0.0) return vec3(1e10);
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const int steps = 16;
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float dt = tMax / float(steps);
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vec3 opticalDepth = vec3(0.0);
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vec3 p = pos;
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for (int i = 0; i < steps; i++){
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float h = length(p) - atmosphereModel_bottom_radius;
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vec3 density = exp(-h / 8.0) * betaRayleigh + exp(-h / 1.2) * betaMie;
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opticalDepth += density * dt;
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p += dir * dt;
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}
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return opticalDepth;
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}
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// Sun/sky irradiance at a camera position (simplified single scattering)
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void GetSunAndSkyIrradiance(vec3 camera, vec3 sunDir, vec3 moonDir,
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out vec3 colorSunlight, out vec3 colorMoonlight,
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out vec3 colorSunSkylight, out vec3 colorMoonSkylight){
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vec3 sunColor = vec3(1.0, 0.98, 0.92);
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vec3 moonColor = vec3(0.5, 0.6, 0.8) * 0.1;
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float sunElevation = sunDir.y;
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float moonElevation = moonDir.y;
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float sunStrength = curve(saturate(sunElevation * 15.0 + 0.5));
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float moonStrength = curve(saturate(-sunElevation * 5.0 + 0.5));
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// Sun disk color by elevation (sunset tint)
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vec3 sunsetTint = mix(vec3(1.0, 0.3, 0.1), vec3(1.0), curve(saturate(sunElevation * 3.0)));
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sunColor *= sunsetTint;
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colorSunlight = sunColor * sunStrength * SUNLIGHT_INTENSITY;
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colorMoonlight = moonColor * moonStrength;
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// Sky irradiance: ambient hemisphere light
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vec3 skyColorDay = vec3(0.55, 0.75, 1.0) * sunStrength * 0.8;
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vec3 skyColorNight = vec3(0.05, 0.08, 0.15) * 0.3;
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vec3 skyColorSunset = vec3(1.0, 0.5, 0.3) * curve(saturate(1.0 - abs(sunElevation) * 4.0)) * 0.3;
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colorSunSkylight = skyColorDay + skyColorSunset;
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colorMoonSkylight = skyColorNight;
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}
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// Sky radiance for a direction (used for the sky panorama and reflections)
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vec3 GetSkyRadiance(vec3 dir, vec3 sunDir){
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dir = normalize(dir);
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sunDir = normalize(sunDir);
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float cosTheta = dot(dir, sunDir);
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// Horizon / elevation response
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float elevation = dir.y;
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// Day sky
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vec3 skyDay = vec3(0.4, 0.62, 0.9) * 0.6;
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skyDay = mix(skyDay, vec3(0.9, 0.95, 1.0), pow(saturate(elevation), 0.6));
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skyDay *= 1.0 - exp(-max(elevation, 0.0) * 3.0);
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// Rayleigh scattering glow around sun
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vec3 rayleigh = RayleighPhase(cosTheta) * betaRayleigh * 1.2;
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// Mie scattering (sun disk)
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float mie = MiePhase(cosTheta) * betaMie * 20.0;
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// Sun disk itself
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float sunDisk = exp(-(1.0 - cosTheta) / (2.0 * SUN_ANGULAR_RADIUS * SUN_ANGULAR_RADIUS));
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vec3 sunColor = vec3(1.0, 0.97, 0.9) * SUNLIGHT_INTENSITY;
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// Sunset tint
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float sunElevation = sunDir.y;
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sunColor *= mix(vec3(1.0, 0.3, 0.1), vec3(1.0), curve(saturate(sunElevation * 3.0)));
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float sunVisible = curve(saturate(sunElevation * 15.0 + 0.5));
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vec3 radiance = skyDay;
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radiance += sunColor * (rayleigh + mie) * sunVisible;
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radiance += sunColor * sunDisk * sunVisible * 80.0;
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// Night sky
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float night = 1.0 - curve(saturate(sunElevation * 10.0 + 0.5));
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radiance += vec3(0.02, 0.03, 0.06) * night;
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// Horizon haze
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float horizon = exp(-abs(elevation) * 4.0);
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radiance += vec3(0.9, 0.7, 0.5) * horizon * sunVisible * 0.1;
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return radiance;
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}
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#endif |