new file mode 100644

Binary files /dev/null and b/doc/05_material_alpha.tga differ

@@ -40,10 +40,17 @@ struct Ray

     }

 };

+//// Material

+struct Material

+{

+    float alpha;

+};

+

 //// Trace

 struct Trace

 {

-    float distance;

+    float    distance;

+    Material material;

     explicit operator bool() const

     {

         return distance < infinity;

@@ -53,22 +60,23 @@ struct Trace

 //// Sphere

 struct Sphere

 {

-    vec3  center;

-    float radius;

+    vec3     center;

+    float    radius;

+    Material material;

     Trace trace(Ray const & ray) const

     {

         auto const offs = center - ray.origin;

         auto const proj = dot(offs, ray.direction);

         if (proj < 0.0F)

-            return {infinity}; // Past.

+            return {infinity, {}}; // Past.

         auto const perp2 = dot(offs, offs) - proj * proj;

         auto const over2 = radius * radius - perp2;

         if (over2 < 0.0F)

-            return {infinity}; // Miss.

+            return {infinity, {}}; // Miss.

         auto const dist = proj - sqrt(over2);

         if (dist < 0.0F)

-            return {infinity}; // Inside.

-        return {dist}; // Hit.

+            return {infinity, {}}; // Inside.

+        return {dist, material}; // Hit.

     }

 };

@@ -81,7 +89,7 @@ struct Scene

     Shapes shapes;

     Trace trace(Ray const & ray) const

     {

-        auto nearest = Trace{infinity};

+        auto nearest = Trace{infinity, {}};

         for (auto const & shape : shapes)

         {

             auto const trace = shape.trace(ray);

@@ -253,12 +261,12 @@ int main(int argc, char const * argv[])

     );

     auto scene = Scene{

         { // shapes

-            Sphere{{   6.0F,  -4.0F,  -24.0F}, 12.0F},

-            Sphere{{   2.0F,   6.0F,  -16.0F},  8.0F},

-            Sphere{{  -4.0F,   0.0F,  -10.0F},  4.0F},

-            Sphere{{   0.0F,  -4.0F,   -6.0F},  1.0F},

-            Sphere{{  -1.1F,   0.8F,   -1.1F},  0.2F},

-            Sphere{{-110.0F, -80.0F, -110.0F}, 20.0F},

+            Sphere{{   6.0F,  -4.0F,  -24.0F}, 12.0F, 1.0F},

+            Sphere{{   2.0F,   6.0F,  -16.0F},  8.0F, 1.0F},

+            Sphere{{  -4.0F,   0.0F,  -10.0F},  4.0F, 1.0F},

+            Sphere{{   0.0F,  -4.0F,   -6.0F},  1.0F, 0.5F},

+            Sphere{{  -1.1F,   0.8F,   -1.1F},  0.2F, 1.0F},

+            Sphere{{-110.0F, -80.0F, -110.0F}, 20.0F, 1.0F},

         },

     };

     //// Render

@@ -267,13 +275,15 @@ int main(int argc, char const * argv[])

         auto ray    = camera.ray(frag_coord, depth_range);

         auto trace  = Trace{};

         auto traces = 0;

-        while ((trace = scene.trace(ray)))

+        auto trans  = 1.0F;

+        while (trans != 0.0F && (trace = scene.trace(ray)))

         {

             ++traces;

+            trans *= 1.0F - trace.material.alpha;

             ray = ray.resumed(trace.distance);

         }

         auto const rgb   = vec3(1.0F / (1.0F + (float)traces));

-        auto const alpha = (bool)traces;

+        auto const alpha = 1.0F - trans;

         return vec4(rgb, alpha);

     });

     //// Finalize