70 lines
2 KiB
GLSL
70 lines
2 KiB
GLSL
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#version 330 core
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layout(location = 0) out vec4 fragColor;
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in VS_OUT {
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vec2 texcoord;
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vec3 vertex_normal;
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vec3 view_vector;
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} fs_in;
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uniform sampler2D color_tex;
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uniform sampler2D transmittance_tex;
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uniform vec3 fg_SunDirection;
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uniform float fg_CameraDistanceToEarthCenter;
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uniform float fg_EarthRadius;
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uniform vec3 fg_CameraViewUp;
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const float ATMOSPHERE_RADIUS = 6471e3;
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// math.glsl
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float M_1_PI();
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// color.glsl
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vec3 eotf_inverse_sRGB(vec3 srgb);
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// normalmap.glsl
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vec3 perturb_normal(vec3 N, vec3 V, vec2 texcoord);
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// atmos_spectral.glsl
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vec4 get_sun_spectral_irradiance();
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vec3 linear_srgb_from_spectral_samples(vec4 L);
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// exposure.glsl
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vec3 apply_exposure(vec3 color);
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void main()
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{
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vec3 albedo = eotf_inverse_sRGB(texture(color_tex, fs_in.texcoord).rgb);
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vec3 N = normalize(fs_in.vertex_normal);
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N = perturb_normal(N, fs_in.view_vector, fs_in.texcoord);
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float NdotL = max(dot(N, fg_SunDirection), 0.0);
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vec3 V = normalize(fs_in.view_vector);
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// Simple Lambertian BRDF
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vec3 color = albedo * M_1_PI() * NdotL
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* linear_srgb_from_spectral_samples(get_sun_spectral_irradiance());
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// Apply aerial perspective
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float normalized_altitude =
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(fg_CameraDistanceToEarthCenter - fg_EarthRadius)
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/ (ATMOSPHERE_RADIUS - fg_EarthRadius);
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float cos_theta = dot(-V, fg_CameraViewUp);
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vec2 uv = vec2(cos_theta * 0.5 + 0.5, clamp(normalized_altitude, 0.0, 1.0));
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vec4 transmittance = texture(transmittance_tex, uv);
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// The proper thing would be to have spectral albedo data for the moon,
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// but that's too much work for little return. Just approximate the
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// transmittance by taking the average of the four spectral samples.
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color *= dot(transmittance, vec4(0.25));
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// Pre-expose
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color = apply_exposure(color);
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// Final color = transmittance * moon color + sky inscattering
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// In this frag shader we output the multiplication part, and the sky
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// in-scattering is added by doing additive blending on top of the skydome.
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fragColor = vec4(color, 1.0);
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}
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