Raymarching – Sky & Sun

Generate Sky & Sun in Ray Marching algorithm is very simple to process. When the map procedure don’t intersect a scene obiect (In my shader Hit variable is false) gl_FragColor set to background color. Is simple way to create it:

1. First define te Sun structure:

   struct Sun {
       vec3 posistion;
       vec3 color;
       float haloSize;
       float haloPower;
       float discSize;
       float discPower;
       float discArea;
       float horizontal;
   };
   Sun sunLight=Sun(vec3(-0.2, 0.2,  -0.4),vec3(1.0,1.0,1.0), 100.0, 0.3, 100.0, 1.5, 0.9, 5.0);

2. Test the intersect a scene object:

       Object sceneObject=rayMarching(ray, rayDir);
       vec3 outColor=vec3(0.0, 0.0, 0.0);
       if (sceneObject.hit){
   ...
           outColor=outColor * lightColor * baseShadow + sceneObject.mat.ambient;
       } else {
           outColor=getSky(sceneObject, ray, rayDir);  
       }
   
       gl_FragColor=vec4(outColor.r, outColor.g, outColor.b, 1.0);

3. If intersect is false result generate background color in the getSky function:

   vec3 getSky(Object sceneObject, vec3 ray, vec3 rayDir){
   
       vec3 skyColor=vec3(0.0);
       float horizontHeight = pow(1.0-max(rayDir.y,0.0), sunLight.horizontal);
       skyColor=mix(vec3(0.0, 0.0, 0.5), vec3(1.0, 0.0, 0.0), horizontHeight);
   
       #if ENABLE_SUN==1
           float sunAmount = max(dot(rayDir, normalize(sunLight.posistion)), 0.0);
           // Sun Halo
           skyColor = skyColor + sunLight.color * pow(sunAmount, sunLight.haloSize) * sunLight.haloPower;
           // Sun Disc
           skyColor = skyColor + sunLight.color * min(pow(sunAmount, sunLight.discSize) * sunLight.discPower, sunLight.discArea);
       #endif
   
       return clamp(skyColor, 0.0, 1.0);
   }

4. To create more funny effect – where intersect if true, create a halo effect in post processing (in future).

Example of this sun effect: