diff --git a/Effects/HDR/atmos-aerial-perspective.eff b/Effects/HDR/atmos-aerial-perspective.eff
index bfdfd044a..62664a5f5 100644
--- a/Effects/HDR/atmos-aerial-perspective.eff
+++ b/Effects/HDR/atmos-aerial-perspective.eff
@@ -3,18 +3,42 @@
Effects/HDR/atmos-aerial-perspective
-
-
-
-
-
-
-
-
+
+
+
+
+
+
+
+
+
+
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+
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+
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+
+
+
-
-
-
@@ -33,25 +57,50 @@
- aerosol_type
- int
-
+ aerosol_absorption_cross_section
+ float-vec4
+
- aerosol_turbidity
+ aerosol_scattering_cross_section
+ float-vec4
+
+
+
+ aerosol_base_density
float
-
+
+
+
+ aerosol_relative_background_density
+ float
+
+
+
+ aerosol_scale_height
+ float
+
+
+
+ fog_density
+ float
+
+
+
+ fog_scale_height
+ float
+
+
+
+ ozone_mean_dobson
+ float
+
ground_albedo
- float
+ float-vec4
-
- month_of_the_year
- int
-
-
diff --git a/Effects/HDR/atmos-sky-view.eff b/Effects/HDR/atmos-sky-view.eff
index 837eb5f97..5c6338ea8 100644
--- a/Effects/HDR/atmos-sky-view.eff
+++ b/Effects/HDR/atmos-sky-view.eff
@@ -3,18 +3,42 @@
Effects/HDR/atmos-sky-view
-
-
-
-
-
-
-
-
+
+
+
+
+
+
+
+
+
+
+
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+
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+
+
-
-
-
@@ -31,25 +55,50 @@
- aerosol_type
- int
-
+ aerosol_absorption_cross_section
+ float-vec4
+
- aerosol_turbidity
+ aerosol_scattering_cross_section
+ float-vec4
+
+
+
+ aerosol_base_density
float
-
+
+
+
+ aerosol_relative_background_density
+ float
+
+
+
+ aerosol_scale_height
+ float
+
+
+
+ fog_density
+ float
+
+
+
+ fog_scale_height
+ float
+
+
+
+ ozone_mean_dobson
+ float
+
ground_albedo
- float
+ float-vec4
-
- month_of_the_year
- int
-
-
diff --git a/Effects/HDR/atmos-transmittance.eff b/Effects/HDR/atmos-transmittance.eff
index 48682a52b..a755decc2 100644
--- a/Effects/HDR/atmos-transmittance.eff
+++ b/Effects/HDR/atmos-transmittance.eff
@@ -3,18 +3,42 @@
Effects/HDR/atmos-transmittance
-
-
-
-
-
-
-
-
+
+
+
+
+
+
+
+
+
+
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+
+
+
+
-
-
-
@@ -26,25 +50,50 @@
- aerosol_type
- int
-
+ aerosol_absorption_cross_section
+ float-vec4
+
- aerosol_turbidity
+ aerosol_scattering_cross_section
+ float-vec4
+
+
+
+ aerosol_base_density
float
-
+
+
+
+ aerosol_relative_background_density
+ float
+
+
+
+ aerosol_scale_height
+ float
+
+
+
+ fog_density
+ float
+
+
+
+ fog_scale_height
+ float
+
+
+
+ ozone_mean_dobson
+ float
+
ground_albedo
- float
+ float-vec4
-
- month_of_the_year
- int
-
-
diff --git a/Nasal/hdr.nas b/Nasal/hdr.nas
new file mode 100644
index 000000000..5343e00ca
--- /dev/null
+++ b/Nasal/hdr.nas
@@ -0,0 +1,33 @@
+# Copyright (C) 2023 Fernando García Liñán
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+#-------------------------------------------------------------------------------
+# Utilities for the HDR Pipeline
+#
+# Shaders usually need to be fed uniforms that are either too expensive to
+# compute on the GPU or can be precomputed once per frame. In this file we
+# transform values from already existing properties into data that can be used
+# by the shaders directly.
+#-------------------------------------------------------------------------------
+
+setprop("/sim/rendering/hdr/atmos/aerosol-absorption-cross-section[0]", 2.8722e-24);
+setprop("/sim/rendering/hdr/atmos/aerosol-absorption-cross-section[1]", 4.6168e-24);
+setprop("/sim/rendering/hdr/atmos/aerosol-absorption-cross-section[2]", 7.9706e-24);
+setprop("/sim/rendering/hdr/atmos/aerosol-absorption-cross-section[3]", 1.3578e-23);
+
+setprop("/sim/rendering/hdr/atmos/aerosol-scattering-cross-section[0]", 1.5908e-22);
+setprop("/sim/rendering/hdr/atmos/aerosol-scattering-cross-section[1]", 1.7711e-22);
+setprop("/sim/rendering/hdr/atmos/aerosol-scattering-cross-section[2]", 2.0942e-22);
+setprop("/sim/rendering/hdr/atmos/aerosol-scattering-cross-section[3]", 2.4033e-22);
+
+setprop("/sim/rendering/hdr/atmos/aerosol-base-density", 1.3681e17);
+setprop("/sim/rendering/hdr/atmos/aerosol-relative-background-density", 1.4619e-17);
+setprop("/sim/rendering/hdr/atmos/aerosol-scale-height", 0.73);
+setprop("/sim/rendering/hdr/atmos/fog-density", 0.0);
+setprop("/sim/rendering/hdr/atmos/fog-scale-height", 1.0);
+setprop("/sim/rendering/hdr/atmos/ozone-mean-dobson", 347.0);
+
+setprop("/sim/rendering/hdr/atmos/ground-albedo[0]", 0.4);
+setprop("/sim/rendering/hdr/atmos/ground-albedo[1]", 0.4);
+setprop("/sim/rendering/hdr/atmos/ground-albedo[2]", 0.4);
+setprop("/sim/rendering/hdr/atmos/ground-albedo[3]", 0.4);
diff --git a/Shaders/HDR/atmos.glsl b/Shaders/HDR/atmos.glsl
index 5c73bc668..c1edb0ecf 100644
--- a/Shaders/HDR/atmos.glsl
+++ b/Shaders/HDR/atmos.glsl
@@ -1,9 +1,24 @@
+/*
+ * Common atmosphere rendering functions
+ *
+ * See https://www.shadertoy.com/view/msXXDS for a more complete description
+ * of what the shader does and more references.
+ *
+ * All 4-component vectors in this file represent values sampled for the
+ * following wavelengths: 630, 560, 490, 430 nm
+ */
+
#version 330 core
-uniform int aerosol_type;
-uniform float aerosol_turbidity;
-uniform float ground_albedo;
-uniform int month_of_the_year;
+uniform vec4 aerosol_absorption_cross_section;
+uniform vec4 aerosol_scattering_cross_section;
+uniform float aerosol_base_density;
+uniform float aerosol_relative_background_density;
+uniform float aerosol_scale_height;
+uniform float fog_density;
+uniform float fog_scale_height;
+uniform float ozone_mean_dobson;
+uniform vec4 ground_albedo;
uniform float fg_EarthRadius;
@@ -19,37 +34,21 @@ const float HENYEY_ASYMMETRY2 = HENYEY_ASYMMETRY*HENYEY_ASYMMETRY;
const vec4 molecular_scattering_coefficient_base =
vec4(6.605e-6, 1.067e-5, 1.842e-5, 3.156e-5);
+/*
+ * Fog scattering/extinction cross section, units m^2 / molecules
+ * Mie theory results for IOR of 1.333. Particle size is a log normal
+ * distribution of mean diameter=15 and std deviation=0.4
+ */
+const vec4 fog_scattering_cross_section =
+ vec4(5.015e-10, 4.987e-10, 4.966e-10, 4.949e-10);
+
/*
* Ozone absorption cross section, units m^2 / molecules
* "High spectral resolution ozone absorption cross-sections"
* by V. Gorshelev et al. (2014).
*/
-const vec4 ozone_cross_section =
- vec4(3.472e-21, 3.914e-21, 1.349e-21, 11.03e-23) * 1e-4f;
-
-const float ozone_mean_monthly_dobson[] = float[](
- 347.0, // January
- 370.0, // February
- 381.0, // March
- 384.0, // April
- 372.0, // May
- 352.0, // June
- 333.0, // July
- 317.0, // August
- 298.0, // September
- 285.0, // October
- 290.0, // November
- 315.0 // December
- );
-const float ozone_height_distribution[] = float[](
- 9.0 / 210.0,
- 14.0 / 210.0,
- 111.0 / 210.0,
- 64.0 / 210.0,
- 6.0 / 210.0,
- 6.0 / 210.0,
- 0.0
- );
+const vec4 ozone_absorption_cross_section =
+ vec4(3.472e-25, 3.914e-25, 1.349e-25, 11.03e-27);
// math.glsl
float M_PI();
@@ -156,131 +155,46 @@ vec4 get_molecular_scattering_coefficient(float h)
}
/*
- * Return the molecular volume absorption coefficient (km^-1) for a given altitude
+ * Return the molecular volume absorption coefficient (m^-1) for a given altitude
* in kilometers.
*/
vec4 get_molecular_absorption_coefficient(float h)
{
- int i = int(clamp(h / 9.0, 0.0, 6.0));
- float density = ozone_height_distribution[i] *
- ozone_mean_monthly_dobson[month_of_the_year-1] * 2.6867e20f; // molecules / m^2
- density /= 9e3; // m^-3
- return ozone_cross_section * density; // m^-1
+ h += 1e-4; // Avoid division by 0
+ float t = log(h) - 3.22261;
+ float density = 3.78547397e17 * (1.0 / h) * exp(-t * t * 5.55555555);
+ return ozone_absorption_cross_section * ozone_mean_dobson * density;
}
/*
* Return the aerosol density for a given altitude in kilometers.
*/
-float get_aerosol_density(float h, float base_density, float height_scale,
- float relative_background_density)
+float get_aerosol_density(float h)
{
- if (aerosol_type == 0) {
- // Only for the Background aerosol type, no dependency on height
- return base_density * (1.0 + relative_background_density);
- } else {
- return base_density * (exp(-h / height_scale) + relative_background_density);
- }
+ return aerosol_base_density * (exp(-h / aerosol_scale_height)
+ + aerosol_relative_background_density);
}
/*
- * Get the aerosol collision coefficients for a given altitude h in km.
- * The two main parameters are the aerosol type (0 to 8), and the turbidity.
- * Every aerosol type expects 5 parameters:
- * - Scattering cross section
- * - Absorption cross section
- * - Base density (km^-3)
- * - Background density (km^-3)
- * - Height scaling parameter
+ * Return the fog volume scattering coefficient (m^-1) for a given altitude in
+ * kilometers.
*
- * This model for aerosols and their corresponding parameters come from
- * "A Physically-Based Spatio-Temporal Sky Model"
- * by Guimera et al. (2018).
+ * Fog (or mist, depending on density) is a special kind of aerosol consisting
+ * of water droplets or ice crystals. Visibility is mostly dependent on fog.
*/
-void get_aerosol_collision_coefficients(in float h,
- out vec4 absorption,
- out vec4 scattering)
+vec4 get_fog_scattering_coefficient(float h)
{
- vec4 aerosol_absorption_cross_section, aerosol_scattering_cross_section;
- float aerosol_base_density, aerosol_background_density, aerosol_height_scale;
- if (aerosol_type == 0) {
- // Background
- aerosol_absorption_cross_section = vec4(4.5517e-19, 5.9269e-19, 6.9143e-19, 8.5228e-19);
- aerosol_scattering_cross_section = vec4(1.8921e-26, 1.6951e-26, 1.7436e-26, 2.1158e-26);
- aerosol_base_density = 2.584e17;
- aerosol_background_density = 2e6;
- } else if (aerosol_type == 1) {
- // Desert-Dust
- aerosol_absorption_cross_section = vec4(4.6758e-16, 4.4654e-16, 4.1989e-16, 4.1493e-16);
- aerosol_scattering_cross_section = vec4(2.9144e-16, 3.1463e-16, 3.3902e-16, 3.4298e-16);
- aerosol_base_density = 1.8662e18;
- aerosol_background_density = 2e6;
- aerosol_height_scale = 2.0;
- } else if (aerosol_type == 2) {
- // Maritime Clean
- aerosol_absorption_cross_section = vec4(6.3312e-19, 7.5567e-19, 9.2627e-19, 1.0391e-18);
- aerosol_scattering_cross_section = vec4(4.6539e-26, 2.721e-26, 4.1104e-26, 5.6249e-26);
- aerosol_base_density = 2.0266e17;
- aerosol_background_density = 2e6;
- aerosol_height_scale = 0.9;
- } else if (aerosol_type == 3) {
- // Maritime Mineral
- aerosol_absorption_cross_section = vec4(6.9365e-19, 7.5951e-19, 8.2423e-19, 8.9101e-19);
- aerosol_scattering_cross_section = vec4(2.3699e-19, 2.2439e-19, 2.2126e-19, 2.021e-19);
- aerosol_base_density = 2.0266e17;
- aerosol_background_density = 2e6;
- aerosol_height_scale = 2.0;
- } else if (aerosol_type == 4) {
- // Polar Antarctic
- aerosol_absorption_cross_section = vec4(1.3399e-16, 1.3178e-16, 1.2909e-16, 1.3006e-16);
- aerosol_scattering_cross_section = vec4(1.5506e-19, 1.809e-19, 2.3069e-19, 2.5804e-19);
- aerosol_base_density = 2.3864e16;
- aerosol_background_density = 2e6;
- aerosol_height_scale = 30.0;
- } else if (aerosol_type == 5) {
- // Polar Arctic
- aerosol_absorption_cross_section = vec4(1.0364e-16, 1.0609e-16, 1.0193e-16, 1.0092e-16);
- aerosol_scattering_cross_section = vec4(2.1609e-17, 2.2759e-17, 2.5089e-17, 2.6323e-17);
- aerosol_base_density = 2.3864e16;
- aerosol_background_density = 2e6;
- aerosol_height_scale = 30.0;
- } else if (aerosol_type == 6) {
- // Remote Continental
- aerosol_absorption_cross_section = vec4(4.5307e-18, 5.0662e-18, 4.4877e-18, 3.7917e-18);
- aerosol_scattering_cross_section = vec4(1.8764e-18, 1.746e-18, 1.6902e-18, 1.479e-18);
- aerosol_base_density = 6.103e18;
- aerosol_background_density = 2e6;
- aerosol_height_scale = 0.73;
- } else if (aerosol_type == 7) {
- // Rural
- aerosol_absorption_cross_section = vec4(5.0393e-23, 8.0765e-23, 1.3823e-22, 2.3383e-22);
- aerosol_scattering_cross_section = vec4(2.6004e-22, 2.4844e-22, 2.8362e-22, 2.7494e-22);
- aerosol_base_density = 8.544e18;
- aerosol_background_density = 2e6;
- aerosol_height_scale = 0.73;
- } else if (aerosol_type == 8) {
- // Urban
- aerosol_absorption_cross_section = vec4(2.8722e-24, 4.6168e-24, 7.9706e-24, 1.3578e-23);
- aerosol_scattering_cross_section = vec4(1.5908e-22, 1.7711e-22, 2.0942e-22, 2.4033e-22);
- aerosol_base_density = 1.3681e20;
- aerosol_background_density = 2e6;
- aerosol_height_scale = 0.73;
+ if (fog_density > 0.0) {
+ return fog_scattering_cross_section * fog_density
+ * exp(-h / fog_scale_height);
+ } else {
+ return vec4(0.0);
}
-
- float aerosol_relative_background_density =
- aerosol_background_density / aerosol_base_density;
-
- float aerosol_density = get_aerosol_density(
- h, aerosol_base_density, aerosol_height_scale,
- aerosol_relative_background_density);
- aerosol_density *= aerosol_turbidity * 1e-3;
-
- absorption = aerosol_absorption_cross_section * aerosol_density;
- scattering = aerosol_scattering_cross_section * aerosol_density;
}
/*
* Get the collision coefficients (scattering and absorption) of the
- * atmospheric medium for a given point at an altitude h.
+ * atmospheric medium for a given point at an altitude h in meters.
*/
void get_atmosphere_collision_coefficients(in float h,
out vec4 aerosol_absorption,
@@ -291,9 +205,19 @@ void get_atmosphere_collision_coefficients(in float h,
{
h *= 1e-3; // To km
h = max(h, 0.0); // In case height is negative
- get_aerosol_collision_coefficients(h, aerosol_absorption, aerosol_scattering);
+
+ // Molecules
molecular_absorption = get_molecular_absorption_coefficient(h);
molecular_scattering = get_molecular_scattering_coefficient(h);
+
+ // Aerosols
+ float aerosol_density = get_aerosol_density(h);
+ aerosol_absorption = aerosol_absorption_cross_section * aerosol_density;
+ aerosol_scattering = aerosol_scattering_cross_section * aerosol_density;
+
+ // Add contribution from fog
+ aerosol_scattering += get_fog_scattering_coefficient(h);
+
extinction =
aerosol_absorption + aerosol_scattering +
molecular_absorption + molecular_scattering;
diff --git a/defaults.xml b/defaults.xml
index 577fb38ad..bb1371f12 100644
--- a/defaults.xml
+++ b/defaults.xml
@@ -535,11 +535,6 @@ Started September 2000 by David Megginson, david@megginson.com
2
0.0
-
- 8
- 1.0
- 0.4
-
0.01
0.005