143 lines
3.9 KiB
GLSL
143 lines
3.9 KiB
GLSL
#type vertex
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#version 450 core
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layout(location = 0) in vec3 a_Position;
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uniform mat4 u_Projection;
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uniform mat4 u_View;
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out vec3 v_LocalPos;
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void main()
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{
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v_LocalPos = a_Position;
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// Remove translation from view matrix
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mat4 rotView = mat4(mat3(u_View));
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vec4 clipPos = u_Projection * rotView * vec4(a_Position, 1.0);
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gl_Position = clipPos.xyww;
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}
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#type fragment
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#version 450 core
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layout(location = 0) out vec4 FragColor;
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in vec3 v_LocalPos;
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// Sky parameters
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uniform vec3 u_SunDirection; // Normalized sun direction
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uniform float u_SunIntensity; // HDR sun brightness
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uniform float u_SunAngularRadius; // Sun angular radius in radians
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uniform vec3 u_SkyColorZenith; // Zenith color (linear)
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uniform vec3 u_SkyColorHorizon; // Horizon color (linear)
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uniform vec3 u_GroundColor; // Ground color (linear)
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uniform float u_SkyExposure; // Sky exposure multiplier
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const float PI = 3.14159265359;
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// Rayleigh scattering approximation
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// Simulates how shorter wavelengths (blue) scatter more at zenith
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vec3 computeRayleighScattering(vec3 direction, vec3 sunDir)
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{
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// Height gradient: zenith (y=1) to horizon (y=0)
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float height = max(direction.y, 0.0);
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// Exponential falloff for more natural sky gradient
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float zenithFactor = pow(height, 0.5);
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// Blend between horizon and zenith colors
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vec3 skyColor = mix(u_SkyColorHorizon, u_SkyColorZenith, zenithFactor);
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// Add slight brightening near horizon (atmospheric haze)
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float horizonGlow = exp(-height * 4.0) * 0.3;
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skyColor += u_SkyColorHorizon * horizonGlow;
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return skyColor;
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}
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// Mie scattering - creates glow around the sun
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vec3 computeMieScattering(vec3 direction, vec3 sunDir)
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{
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float cosTheta = dot(direction, sunDir);
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// Henyey-Greenstein phase function approximation
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// g controls asymmetry (0.76 gives forward scattering)
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float g = 0.76;
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float g2 = g * g;
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float phase = (1.0 - g2) / (4.0 * PI * pow(1.0 + g2 - 2.0 * g * cosTheta, 1.5));
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// Scale and color the Mie scattering
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// Warm color for sunset-like glow
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vec3 mieColor = vec3(1.0, 0.9, 0.7);
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return mieColor * phase * 0.15;
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}
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// Sun disc with soft edge
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vec3 computeSunDisc(vec3 direction, vec3 sunDir)
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{
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float cosTheta = dot(direction, sunDir);
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float sunCosAngle = cos(u_SunAngularRadius);
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// Soft edge using smoothstep
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float edgeSoftness = u_SunAngularRadius * 0.3;
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float sunDisc = smoothstep(
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cos(u_SunAngularRadius + edgeSoftness),
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sunCosAngle,
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cosTheta
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);
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// HDR sun color (slightly warm)
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vec3 sunColor = vec3(1.0, 0.95, 0.9) * u_SunIntensity;
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return sunColor * sunDisc;
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}
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void main()
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{
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vec3 direction = normalize(v_LocalPos);
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vec3 sunDir = normalize(u_SunDirection);
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vec3 color = vec3(0.0);
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// Check if we're looking at sky or ground
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if (direction.y > -0.02)
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{
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// Sky hemisphere
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// Base sky color with Rayleigh scattering
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vec3 skyColor = computeRayleighScattering(direction, sunDir);
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// Add Mie scattering (sun glow)
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vec3 mie = computeMieScattering(direction, sunDir);
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skyColor += mie;
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// Add sun disc (only if sun is above horizon)
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if (sunDir.y > 0.0)
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{
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vec3 sunDisc = computeSunDisc(direction, sunDir);
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skyColor += sunDisc;
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}
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// Apply exposure
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color = skyColor * u_SkyExposure;
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// Soft transition to ground at horizon
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float horizonBlend = smoothstep(-0.02, 0.05, direction.y);
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color = mix(u_GroundColor * u_SkyExposure * 0.5, color, horizonBlend);
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}
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else
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{
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// Ground hemisphere
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// Darken towards nadir for depth
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float groundFade = smoothstep(-1.0, -0.1, direction.y);
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color = u_GroundColor * u_SkyExposure * 0.5 * groundFade;
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}
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// Output linear HDR (no tonemapping - IBL pipeline will process this)
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FragColor = vec4(color, 1.0);
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}
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