source/effects/sky.cpp

   1 #include <msp/geometry/hypersphere.h>
   2 #include <msp/geometry/ray.h>
   3 #include "light.h"
   4 #include "mesh.h"
   5 #include "renderer.h"
   6 #include "resources.h"
   7 #include "sky.h"
   8
   9 using namespace std;
  10
  11 namespace Msp {
  12 namespace GL {
  13
  14 Sky::Sky(Renderable &r, Light &s):
  15         Effect(r),
  16         sun(s),
  17         transmittance_lookup(128, 64, (RENDER_COLOR, RGB16F)),
  18         transmittance_shprog(Resources::get_global().get<Program>("_sky_transmittance.glsl.shader")),
  19         transmittance_lookup_dirty(true),
  20         distant(256, 128, (RENDER_COLOR, RGB16F)),
  21         distant_shprog(Resources::get_global().get<Program>("_sky_distant.glsl.shader")),
  22         fullscreen_mesh(Resources::get_global().get<Mesh>("_fullscreen_quad.mesh")),
  23         backdrop_shprog(Resources::get_global().get<Program>("_sky_backdrop.glsl.shader")),
  24         sampler(Resources::get_global().get<Sampler>("_linear_clamp.samp")),
  25         wrap_sampler(Resources::get_global().get<Sampler>("_linear_clamp_v.samp")),
  26         rendered(false)
  27 {
  28         shdata.uniform("n_steps", 50);
  29
  30         set_planet(Planet::earth());
  31         set_view_height(5.0f);
  32 }
  33
  34 void Sky::set_planet(const Planet &p)
  35 {
  36         planet = p;
  37         shdata.uniform("events.rayleigh_scatter", planet.rayleigh_scatter.r, planet.rayleigh_scatter.g, planet.rayleigh_scatter.b);
  38         shdata.uniform("events.mie_scatter", planet.mie_scatter.r, planet.mie_scatter.g, planet.mie_scatter.b);
  39         shdata.uniform("events.mie_absorb", planet.mie_absorb.r, planet.mie_absorb.g, planet.mie_absorb.b);
  40         shdata.uniform("events.ozone_absorb", planet.ozone_absorb.r, planet.ozone_absorb.g, planet.ozone_absorb.b);
  41         shdata.uniform("rayleigh_density_decay", planet.rayleigh_density_decay);
  42         shdata.uniform("mie_density_decay", planet.mie_density_decay);
  43         shdata.uniform("ozone_band_center", planet.ozone_band_center);
  44         shdata.uniform("ozone_band_extent", planet.ozone_band_extent);
  45         shdata.uniform("atmosphere_thickness", planet.atmosphere_thickness);
  46         shdata.uniform("planet_radius", planet.planet_radius);
  47         shdata.uniform("ground_albedo", planet.ground_albedo.r, planet.ground_albedo.g, planet.ground_albedo.b);
  48 }
  49
  50 void Sky::set_view_height(float h)
  51 {
  52         view_height = h;
  53         shdata.uniform("view_height", h);
  54 }
  55
  56 Color Sky::get_transmittance(const Vector3 &look_dir)
  57 {
  58         Vector3 pos(0.0f, 0.0f, view_height);
  59         Vector3 planet_center(0.0f, 0.0f, -planet.planet_radius);
  60
  61         Geometry::Ray<float, 3> ray(pos-planet_center, look_dir);
  62         Geometry::HyperSphere<float, 3> surface(planet.planet_radius);
  63         Geometry::SurfacePoint<float, 3> intersection;
  64         if(surface.get_intersections(ray, &intersection, 1))
  65                 return Color(0.0f);
  66
  67         Geometry::HyperSphere<float, 3> space(planet.planet_radius+planet.atmosphere_thickness);
  68         if(!space.get_intersections(ray, &intersection, 1))
  69                 return Color(1.0f);
  70
  71         float step_size = intersection.distance/50;
  72
  73         Color path_extinction(0.0f);
  74         for(unsigned i=0; i<50; ++i)
  75         {
  76                 Vector3 from_center = pos-planet_center;
  77                 float height = from_center.norm()-planet.planet_radius;
  78
  79                 Color rayleigh_scatter = planet.rayleigh_scatter*exp(height/planet.rayleigh_density_decay);
  80                 Color mie_scatter = planet.mie_scatter*exp(height/planet.mie_density_decay);
  81                 Color mie_absorb = planet.mie_absorb*exp(height/planet.mie_density_decay);
  82                 Color ozone_absorb = planet.ozone_absorb*max(1.0f-abs(height-planet.ozone_band_center)/planet.ozone_band_extent, 0.0f);
  83
  84                 path_extinction = path_extinction+(rayleigh_scatter+mie_scatter+mie_absorb+ozone_absorb)*step_size;
  85                 pos += look_dir*step_size;
  86         }
  87
  88         return Color(exp(-path_extinction.r), exp(-path_extinction.g), exp(-path_extinction.b));
  89 }
  90
  91 void Sky::setup_frame(Renderer &renderer)
  92 {
  93         if(rendered)
  94                 return;
  95
  96         rendered = true;
  97
  98         shdata.uniform("light_color", sun.get_color());
  99         shdata.uniform("light_dir", sun.get_position().slice<3>(0));
 100         sun.set_transmittance(get_transmittance(normalize(sun.get_position().slice<3>(0))));
 101
 102         Renderer::Push push(renderer);
 103
 104         if(transmittance_lookup_dirty)
 105         {
 106                 transmittance_lookup_dirty = false;
 107                 renderer.set_framebuffer(&transmittance_lookup.get_framebuffer());
 108                 renderer.set_shader_program(&transmittance_shprog, &shdata);
 109                 fullscreen_mesh.draw(renderer);
 110         }
 111
 112         renderer.set_framebuffer(&distant.get_framebuffer());
 113         renderer.set_shader_program(&distant_shprog, &shdata);
 114         renderer.set_texture("transmittance_lookup", &transmittance_lookup.get_target_texture(0), &sampler);
 115         fullscreen_mesh.draw(renderer);
 116
 117         renderable.setup_frame(renderer);
 118 }
 119
 120 void Sky::finish_frame()
 121 {
 122         if(rendered)
 123         {
 124                 rendered = false;
 125                 renderable.finish_frame();
 126         }
 127 }
 128
 129 void Sky::render(Renderer &renderer, Tag tag) const
 130 {
 131         renderable.render(renderer, tag);
 132
 133         Renderer::Push push(renderer);
 134
 135         renderer.set_shader_program(&backdrop_shprog, &shdata);
 136         renderer.set_texture("distant", &distant.get_target_texture(0), &wrap_sampler);
 137         fullscreen_mesh.draw(renderer);
 138 }
 139
 140 void Sky::set_debug_name(const string &name)
 141 {
 142 #ifdef DEBUG
 143         transmittance_lookup.set_debug_name(name+" [RT:transmittance]");
 144         distant.set_debug_name(name+" [RT:distant]");
 145         shdata.set_debug_name(name+" [UBO]");
 146 #else
 147         (void)name;
 148 #endif
 149 }
 150
 151
 152 Sky::Planet::Planet():
 153         rayleigh_scatter(0.0f),
 154         mie_scatter(0.0f),
 155         mie_absorb(0.0f),
 156         ozone_absorb(0.0f),
 157         rayleigh_density_decay(1e3f),
 158         mie_density_decay(1e3f),
 159         ozone_band_center(1e4f),
 160         ozone_band_extent(1e2f),
 161         atmosphere_thickness(2e4f),
 162         planet_radius(1e6f)
 163 { }
 164
 165 Sky::Planet Sky::Planet::earth()
 166 {
 167         Planet planet;
 168         planet.rayleigh_scatter = Color(5.802e-6f, 13.558e-6f, 33.1e-6f);
 169         planet.mie_scatter = Color(3.996e-6f, 3.996e-6f, 3.996e-6f);
 170         planet.mie_absorb = Color(4.4e-6f, 4.4e-6f, 4.4e-6f);
 171         planet.ozone_absorb = Color(0.65e-6f, 1.881e-6f, 0.085e-6f);
 172         planet.rayleigh_density_decay = -8e3f;
 173         planet.mie_density_decay = -1.2e3f;
 174         planet.ozone_band_center = 25e3f;
 175         planet.ozone_band_extent = 15e3f;
 176         planet.atmosphere_thickness = 1e5f;
 177         planet.planet_radius = 6.36e6f;
 178         return planet;
 179 }
 180
 181 } // namespace GL
 182 } // namespace Msp