Modify sunlight color based on transmittance of the atmosphere

[libs/gl.git] / source / effects / sky.cpp

diff --git a/source/effects/sky.cpp b/source/effects/sky.cpp
index baf4864ad02256b1b83a332541369241c5e8f019..9a5f73bc73f8d1b6405c810935721b220b53804d 100644 (file)
--- a/source/effects/sky.cpp
+++ b/source/effects/sky.cpp
@@ -1,3 +1,5 @@
+#include <msp/geometry/hypersphere.h>
+#include <msp/geometry/ray.h>
 #include "light.h"
 #include "mesh.h"
 #include "renderer.h"
@@ -9,7 +11,7 @@ using namespace std;
 namespace Msp {
 namespace GL {
 
-Sky::Sky(Renderable &r, const Light &s):
+Sky::Sky(Renderable &r, Light &s):
        Effect(r),
        sun(s),
        transmittance_lookup(128, 64, (RENDER_COLOR, RGB16F)),
@@ -29,8 +31,9 @@ Sky::Sky(Renderable &r, const Light &s):
        set_view_height(5.0f);
 }
 
-void Sky::set_planet(const Planet &planet)
+void Sky::set_planet(const Planet &p)
 {
+       planet = p;
        shdata.uniform("events.rayleigh_scatter", planet.rayleigh_scatter.r, planet.rayleigh_scatter.g, planet.rayleigh_scatter.b);
        shdata.uniform("events.mie_scatter", planet.mie_scatter.r, planet.mie_scatter.g, planet.mie_scatter.b);
        shdata.uniform("events.mie_absorb", planet.mie_absorb.r, planet.mie_absorb.g, planet.mie_absorb.b);
@@ -46,9 +49,45 @@ void Sky::set_planet(const Planet &planet)
 
 void Sky::set_view_height(float h)
 {
+       view_height = h;
        shdata.uniform("view_height", h);
 }
 
+Color Sky::get_transmittance(const Vector3 &look_dir)
+{
+       Vector3 pos(0.0f, 0.0f, view_height);
+       Vector3 planet_center(0.0f, 0.0f, -planet.planet_radius);
+
+       Geometry::Ray<float, 3> ray(pos-planet_center, look_dir);
+       Geometry::HyperSphere<float, 3> surface(planet.planet_radius);
+       Geometry::SurfacePoint<float, 3> intersection;
+       if(surface.get_intersections(ray, &intersection, 1))
+               return Color(0.0f);
+
+       Geometry::HyperSphere<float, 3> space(planet.planet_radius+planet.atmosphere_thickness);
+       if(!space.get_intersections(ray, &intersection, 1))
+               return Color(1.0f);
+
+       float step_size = intersection.distance/50;
+
+       Color path_extinction(0.0f);
+       for(unsigned i=0; i<50; ++i)
+       {
+               Vector3 from_center = pos-planet_center;
+               float height = from_center.norm()-planet.planet_radius;
+
+               Color rayleigh_scatter = planet.rayleigh_scatter*exp(height/planet.rayleigh_density_decay);
+               Color mie_scatter = planet.mie_scatter*exp(height/planet.mie_density_decay);
+               Color mie_absorb = planet.mie_absorb*exp(height/planet.mie_density_decay);
+               Color ozone_absorb = planet.ozone_absorb*max(1.0f-abs(height-planet.ozone_band_center)/planet.ozone_band_extent, 0.0f);
+
+               path_extinction = path_extinction+(rayleigh_scatter+mie_scatter+mie_absorb+ozone_absorb)*step_size;
+               pos += look_dir*step_size;
+       }
+
+       return Color(exp(-path_extinction.r), exp(-path_extinction.g), exp(-path_extinction.b));
+}
+
 void Sky::setup_frame(Renderer &renderer)
 {
        if(rendered)
@@ -58,6 +97,7 @@ void Sky::setup_frame(Renderer &renderer)
 
        shdata.uniform("light_color", sun.get_color());
        shdata.uniform("light_dir", sun.get_position().slice<3>(0));
+       sun.set_transmittance(get_transmittance(normalize(sun.get_position().slice<3>(0))));
 
        Renderer::Push push(renderer);