checkerboard

.gitignore

@@ -0,0 +1,3 @@
+# Ignore content built with CMake
+build/
+

tinyraytracer.cpp

@@ -69,7 +69,20 @@ bool scene_intersect(const Vec3f &orig, const Vec3f &dir, const std::vector<Sphe
             material = spheres[i].material;
         }
     }
-    return spheres_dist<1000;
+
+    float checkerboard_dist = std::numeric_limits<float>::max();
+    if (fabs(dir.y)>1e-3)  {
+        float d = -(orig.y+4)/dir.y; // the checkerboard plane has equation y = -4
+        Vec3f pt = orig + dir*d;
+        if (d>0 && fabs(pt.x)<10 && pt.z<-10 && pt.z>-30 && d<spheres_dist) {
+            checkerboard_dist = d;
+            hit = pt;
+            N = Vec3f(0,1,0);
+            material.diffuse_color = (int(.5*hit.x+1000) + int(.5*hit.z)) & 1 ? Vec3f(1,1,1) : Vec3f(1, .7, .3);
+            material.diffuse_color = material.diffuse_color*.3;
+        }
+    }
+    return std::min(spheres_dist, checkerboard_dist)<1000;
 }
 
 Vec3f cast_ray(const Vec3f &orig, const Vec3f &dir, const std::vector<Sphere> &spheres, const std::vector<Light> &lights, size_t depth=0) {