Implement BVH

CMakeLists.txt

@@ -3,6 +3,8 @@ project(Raytracer VERSION 0.1.0 LANGUAGES C CXX)
 
 add_executable(Raytracer 
     ImageGenerator.cpp
+    aabb.h
+    bvh.h
     camera.h
     colour.h
     hittable.h

ImageGenerator.cpp

@@ -1,4 +1,5 @@
 #include "rayTracer.h"
+#include "bvh.h"
 #include "camera.h"
 #include "hittable.h"
 #include "hittableList.h"
@@ -9,18 +10,6 @@ int main(void) {
     // World. 
     hittableList world;
 
-    // auto groundMaterial = make_shared<lambertian>(colour(0.1, 0.0, 0.0));
-    // auto centreMaterial = make_shared<lambertian>(colour(0.1, 0.2, 0.5));
-    // auto leftMaterial   = make_shared<dielectric>(1.50);
-    // auto bubbleMaterial = make_shared<dielectric>(1.00 / 1.50);
-    // auto rightMaterial  = make_shared<metal>(colour(1.0, 0.0, 0.0), 1.0);
-
-    // world.add(make_shared<sphere>(point3( 0.0, -100.5, -1.0), 100.0, groundMaterial));
-    // world.add(make_shared<sphere>(point3( 0.0,    0.0, -1.2),   0.5, centreMaterial));
-    // world.add(make_shared<sphere>(point3(-1.0,    0.0, -1.0),   0.5, leftMaterial));
-    // world.add(make_shared<sphere>(point3(-1.0,    0.0, -1.0),   0.4, bubbleMaterial));
-    // world.add(make_shared<sphere>(point3( 1.0,    0.0, -1.0),   0.5, rightMaterial));
-
     // Code from the book. 
     auto ground_material = make_shared<lambertian>(colour(0.5, 0.5, 0.5));
     world.add(make_shared<sphere>(point3(0,-1000,0), 1000, ground_material));
@@ -65,6 +54,8 @@ int main(void) {
     auto material3 = make_shared<metal>(colour(0.7, 0.6, 0.5), 0.0);
     world.add(make_shared<sphere>(point3(4, 1, 0), 1.0, material3));
 
+    world = hittableList(make_shared<bvh_node>(world));
+
     // Camera. 
     camera cam;
     cam.aspectRatio = 16.0 / 9.0;

aabb.h

@@ -0,0 +1,58 @@
+#ifndef AABB_H
+#define AABB_H
+
+#include "rayTracer.h"
+
+class aabb {
+  public:
+    interval x, y, z;
+
+    aabb() {} // The default AABB is empty, since intervals are empty by default.
+
+    aabb(const interval& x, const interval& y, const interval& z) : x(x), y(y), z(z) {}
+
+    aabb(const point3& a, const point3& b) {
+        // Treat the two points a and b as extrema for the bounding box, so we don't require a particular minimum/maximum coordinate order.
+        x = (a[0] <= b[0]) ? interval(a[0], b[0]) : interval(b[0], a[0]);
+        y = (a[1] <= b[1]) ? interval(a[1], b[1]) : interval(b[1], a[1]);
+        z = (a[2] <= b[2]) ? interval(a[2], b[2]) : interval(b[2], a[2]);
+    }
+
+    aabb(const aabb& box0, const aabb& box1) {
+        x = interval(box0.x, box1.x);
+        y = interval(box0.y, box1.y);
+        z = interval(box0.z, box1.z);
+    }
+
+    const interval& axisInterval(int n) const {
+        if (n == 1) return y;
+        if (n == 2) return z;
+        return x;
+    }
+
+    bool hit(const ray& r, interval rayT) const {
+        const point3& rayOrigin = r.origin();
+        const vec3& rayDirection  = r.direction();
+
+        for (int axis = 0; axis < 3; axis++) {
+            const interval& ax = axisInterval(axis);
+            const double adInv = 1.0 / rayDirection[axis];
+
+            auto t0 = (ax.min - rayOrigin[axis]) * adInv;
+            auto t1 = (ax.max - rayOrigin[axis]) * adInv;
+
+            if (t0 < t1) {
+                if (t0 > rayT.min) rayT.min = t0;
+                if (t1 < rayT.max) rayT.max = t1;
+            } else {
+                if (t1 > rayT.min) rayT.min = t1;
+                if (t0 < rayT.max) rayT.max = t0;
+            }
+
+            if (rayT.max <= rayT.min) return false;
+        }
+        return true;
+    }
+};
+
+#endif

build/.cmake/api/v1/reply/codemodel-v2-f57fe542ed13663d4779.json

@@ -39,7 +39,7 @@
 				{
 					"directoryIndex" : 0,
 					"id" : "Raytracer::@6890427a1f51a3e7e1df",
-					"jsonFile" : "target-Raytracer-Debug-de18b889ec06b3c1ffd0.json",
+					"jsonFile" : "target-Raytracer-Debug-53e51d7b7c539400eaa2.json",
 					"name" : "Raytracer",
 					"projectIndex" : 0
 				}

build/.cmake/api/v1/reply/index-2024-07-08T20-14-45-0400.json

@@ -26,7 +26,7 @@
 	"objects" : 
 	[
 		{
-			"jsonFile" : "codemodel-v2-3325df503f174f7a816b.json",
+			"jsonFile" : "codemodel-v2-f57fe542ed13663d4779.json",
 			"kind" : "codemodel",
 			"version" : 
 			{
@@ -99,7 +99,7 @@
 						}
 					},
 					{
-						"jsonFile" : "codemodel-v2-3325df503f174f7a816b.json",
+						"jsonFile" : "codemodel-v2-f57fe542ed13663d4779.json",
 						"kind" : "codemodel",
 						"version" : 
 						{

build/.cmake/api/v1/reply/target-Raytracer-Debug-53e51d7b7c539400eaa2.json

@@ -90,7 +90,9 @@
 				7,
 				8,
 				9,
-				10
+				10,
+				11,
+				12
 			]
 		}
 	],
@@ -102,6 +104,16 @@
 			"path" : "ImageGenerator.cpp",
 			"sourceGroupIndex" : 0
 		},
+		{
+			"backtrace" : 1,
+			"path" : "aabb.h",
+			"sourceGroupIndex" : 1
+		},
+		{
+			"backtrace" : 1,
+			"path" : "bvh.h",
+			"sourceGroupIndex" : 1
+		},
 		{
 			"backtrace" : 1,
 			"path" : "camera.h",

build/CMakeFiles/Raytracer.dir/ImageGenerator.cpp.o.d

@@ -195,11 +195,18 @@ CMakeFiles/Raytracer.dir/ImageGenerator.cpp.o: \
  /home/cjsatnarine/Code/Raytracer/interval.h \
  /home/cjsatnarine/Code/Raytracer/vec3.h \
  /home/cjsatnarine/Code/Raytracer/ray.h \
- /home/cjsatnarine/Code/Raytracer/camera.h \
+ /home/cjsatnarine/Code/Raytracer/bvh.h \
+ /home/cjsatnarine/Code/Raytracer/aabb.h /usr/include/c++/13/algorithm \
+ /usr/include/c++/13/bits/stl_algo.h \
+ /usr/include/c++/13/bits/algorithmfwd.h \
+ /usr/include/c++/13/bits/stl_heap.h \
+ /usr/include/c++/13/bits/uniform_int_dist.h \
+ /usr/include/c++/13/pstl/glue_algorithm_defs.h \
  /home/cjsatnarine/Code/Raytracer/hittable.h \
- /home/cjsatnarine/Code/Raytracer/material.h \
  /home/cjsatnarine/Code/Raytracer/hittableList.h \
  /usr/include/c++/13/vector /usr/include/c++/13/bits/stl_vector.h \
  /usr/include/c++/13/bits/stl_bvector.h \
  /usr/include/c++/13/bits/vector.tcc \
+ /home/cjsatnarine/Code/Raytracer/camera.h \
+ /home/cjsatnarine/Code/Raytracer/material.h \
  /home/cjsatnarine/Code/Raytracer/sphere.h

build/CMakeFiles/Raytracer.dir/compiler_depend.internal

@@ -3,6 +3,8 @@
 
 CMakeFiles/Raytracer.dir/ImageGenerator.cpp.o
  /home/cjsatnarine/Code/Raytracer/ImageGenerator.cpp
+ /home/cjsatnarine/Code/Raytracer/aabb.h
+ /home/cjsatnarine/Code/Raytracer/bvh.h
  /home/cjsatnarine/Code/Raytracer/camera.h
  /home/cjsatnarine/Code/Raytracer/colour.h
  /home/cjsatnarine/Code/Raytracer/hittable.h
@@ -16,9 +18,11 @@ CMakeFiles/Raytracer.dir/ImageGenerator.cpp.o
  /usr/include/alloca.h
  /usr/include/asm-generic/errno-base.h
  /usr/include/asm-generic/errno.h
+ /usr/include/c++/13/algorithm
  /usr/include/c++/13/backward/auto_ptr.h
  /usr/include/c++/13/backward/binders.h
  /usr/include/c++/13/bit
+ /usr/include/c++/13/bits/algorithmfwd.h
  /usr/include/c++/13/bits/align.h
  /usr/include/c++/13/bits/alloc_traits.h
  /usr/include/c++/13/bits/allocated_ptr.h
@@ -67,10 +71,12 @@ CMakeFiles/Raytracer.dir/ImageGenerator.cpp.o
  /usr/include/c++/13/bits/shared_ptr_base.h
  /usr/include/c++/13/bits/specfun.h
  /usr/include/c++/13/bits/std_abs.h
+ /usr/include/c++/13/bits/stl_algo.h
  /usr/include/c++/13/bits/stl_algobase.h
  /usr/include/c++/13/bits/stl_bvector.h
  /usr/include/c++/13/bits/stl_construct.h
  /usr/include/c++/13/bits/stl_function.h
+ /usr/include/c++/13/bits/stl_heap.h
  /usr/include/c++/13/bits/stl_iterator.h
  /usr/include/c++/13/bits/stl_iterator_base_funcs.h
  /usr/include/c++/13/bits/stl_iterator_base_types.h
@@ -83,6 +89,7 @@ CMakeFiles/Raytracer.dir/ImageGenerator.cpp.o
  /usr/include/c++/13/bits/streambuf_iterator.h
  /usr/include/c++/13/bits/string_view.tcc
  /usr/include/c++/13/bits/stringfwd.h
+ /usr/include/c++/13/bits/uniform_int_dist.h
  /usr/include/c++/13/bits/unique_ptr.h
  /usr/include/c++/13/bits/uses_allocator.h
  /usr/include/c++/13/bits/uses_allocator_args.h
@@ -117,6 +124,7 @@ CMakeFiles/Raytracer.dir/ImageGenerator.cpp.o
  /usr/include/c++/13/new
  /usr/include/c++/13/ostream
  /usr/include/c++/13/pstl/execution_defs.h
+ /usr/include/c++/13/pstl/glue_algorithm_defs.h
  /usr/include/c++/13/pstl/glue_memory_defs.h
  /usr/include/c++/13/pstl/pstl_config.h
  /usr/include/c++/13/stdexcept

build/CMakeFiles/Raytracer.dir/compiler_depend.make

@@ -2,6 +2,8 @@
 # Generated by "Unix Makefiles" Generator, CMake Version 3.28
 
 CMakeFiles/Raytracer.dir/ImageGenerator.cpp.o: /home/cjsatnarine/Code/Raytracer/ImageGenerator.cpp \
+  /home/cjsatnarine/Code/Raytracer/aabb.h \
+  /home/cjsatnarine/Code/Raytracer/bvh.h \
   /home/cjsatnarine/Code/Raytracer/camera.h \
   /home/cjsatnarine/Code/Raytracer/colour.h \
   /home/cjsatnarine/Code/Raytracer/hittable.h \
@@ -15,9 +17,11 @@ CMakeFiles/Raytracer.dir/ImageGenerator.cpp.o: /home/cjsatnarine/Code/Raytracer/
   /usr/include/alloca.h \
   /usr/include/asm-generic/errno-base.h \
   /usr/include/asm-generic/errno.h \
+  /usr/include/c++/13/algorithm \
   /usr/include/c++/13/backward/auto_ptr.h \
   /usr/include/c++/13/backward/binders.h \
   /usr/include/c++/13/bit \
+  /usr/include/c++/13/bits/algorithmfwd.h \
   /usr/include/c++/13/bits/align.h \
   /usr/include/c++/13/bits/alloc_traits.h \
   /usr/include/c++/13/bits/allocated_ptr.h \
@@ -66,10 +70,12 @@ CMakeFiles/Raytracer.dir/ImageGenerator.cpp.o: /home/cjsatnarine/Code/Raytracer/
   /usr/include/c++/13/bits/shared_ptr_base.h \
   /usr/include/c++/13/bits/specfun.h \
   /usr/include/c++/13/bits/std_abs.h \
+  /usr/include/c++/13/bits/stl_algo.h \
   /usr/include/c++/13/bits/stl_algobase.h \
   /usr/include/c++/13/bits/stl_bvector.h \
   /usr/include/c++/13/bits/stl_construct.h \
   /usr/include/c++/13/bits/stl_function.h \
+  /usr/include/c++/13/bits/stl_heap.h \
   /usr/include/c++/13/bits/stl_iterator.h \
   /usr/include/c++/13/bits/stl_iterator_base_funcs.h \
   /usr/include/c++/13/bits/stl_iterator_base_types.h \
@@ -82,6 +88,7 @@ CMakeFiles/Raytracer.dir/ImageGenerator.cpp.o: /home/cjsatnarine/Code/Raytracer/
   /usr/include/c++/13/bits/streambuf_iterator.h \
   /usr/include/c++/13/bits/string_view.tcc \
   /usr/include/c++/13/bits/stringfwd.h \
+  /usr/include/c++/13/bits/uniform_int_dist.h \
   /usr/include/c++/13/bits/unique_ptr.h \
   /usr/include/c++/13/bits/uses_allocator.h \
   /usr/include/c++/13/bits/uses_allocator_args.h \
@@ -116,6 +123,7 @@ CMakeFiles/Raytracer.dir/ImageGenerator.cpp.o: /home/cjsatnarine/Code/Raytracer/
   /usr/include/c++/13/new \
   /usr/include/c++/13/ostream \
   /usr/include/c++/13/pstl/execution_defs.h \
+  /usr/include/c++/13/pstl/glue_algorithm_defs.h \
   /usr/include/c++/13/pstl/glue_memory_defs.h \
   /usr/include/c++/13/pstl/pstl_config.h \
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@@ -325,8 +333,6 @@ CMakeFiles/Raytracer.dir/ImageGenerator.cpp.o: /home/cjsatnarine/Code/Raytracer/
 
 /usr/include/x86_64-linux-gnu/bits/iscanonical.h:
 
-/usr/include/x86_64-linux-gnu/bits/fp-logb.h:
-
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@@ -385,13 +391,15 @@ CMakeFiles/Raytracer.dir/ImageGenerator.cpp.o: /home/cjsatnarine/Code/Raytracer/
 
 /usr/include/c++/13/tr1/hypergeometric.tcc:
 
-/usr/include/x86_64-linux-gnu/bits/types/__fpos_t.h:
+/usr/include/c++/13/tr1/exp_integral.tcc:
 
-/usr/include/c++/13/bits/refwrap.h:
+/usr/include/c++/13/tr1/ell_integral.tcc:
 
-/usr/include/c++/13/debug/debug.h:
+/usr/include/features-time64.h:
 
-/usr/include/c++/13/stdexcept:
+/usr/include/c++/13/string_view:
+
+/usr/include/c++/13/string:
 
 /usr/include/c++/13/bits/ostream_insert.h:
 
@@ -415,22 +423,10 @@ CMakeFiles/Raytracer.dir/ImageGenerator.cpp.o: /home/cjsatnarine/Code/Raytracer/
 
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-/usr/include/x86_64-linux-gnu/bits/math-vector.h:
-
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-/usr/include/c++/13/bits/nested_exception.h:
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@@ -465,8 +461,52 @@ CMakeFiles/Raytracer.dir/ImageGenerator.cpp.o: /home/cjsatnarine/Code/Raytracer/
 
 /usr/include/alloca.h:
 
+/usr/include/x86_64-linux-gnu/bits/endianness.h:
+
+/usr/include/c++/13/tr1/poly_laguerre.tcc:
+
+/usr/include/c++/13/bits/basic_string.h:
+
+/usr/include/c++/13/bits/specfun.h:
+
 /home/cjsatnarine/Code/Raytracer/rayTracer.h:
 
+/usr/include/c++/13/bits/cxxabi_forced.h:
+
+/home/cjsatnarine/Code/Raytracer/vec3.h:
+
+/home/cjsatnarine/Code/Raytracer/colour.h:
+
+/home/cjsatnarine/Code/Raytracer/hittable.h:
+
+/usr/include/c++/13/backward/binders.h:
+
+/home/cjsatnarine/Code/Raytracer/aabb.h:
+
+/usr/include/x86_64-linux-gnu/bits/waitflags.h:
+
+/usr/include/c++/13/bits/unique_ptr.h:
+
+/usr/include/c++/13/bits/align.h:
+
+/usr/include/c++/13/bits/nested_exception.h:
+
+/home/cjsatnarine/Code/Raytracer/bvh.h:
+
+/usr/include/c++/13/bits/ostream.tcc:
+
+/usr/include/x86_64-linux-gnu/c++/13/bits/c++config.h:
+
+/usr/include/c++/13/bits/ios_base.h:
+
+/home/cjsatnarine/Code/Raytracer/ImageGenerator.cpp:
+
+/usr/include/asm-generic/errno-base.h:
+
+/usr/include/x86_64-linux-gnu/bits/math-vector.h:
+
+/usr/include/c++/13/bits/hash_bytes.h:
+
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 /usr/include/c++/13/bits/predefined_ops.h:
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+/usr/include/x86_64-linux-gnu/bits/types/error_t.h:
 
-/home/cjsatnarine/Code/Raytracer/colour.h:
+/usr/include/x86_64-linux-gnu/bits/mathcalls-helper-functions.h:
 
-/usr/include/x86_64-linux-gnu/bits/waitflags.h:
+/home/cjsatnarine/Code/Raytracer/ray.h:
 
-/usr/include/c++/13/bits/align.h:
+/usr/include/c++/13/bits/stl_raw_storage_iter.h:
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@@ -509,8 +533,26 @@ CMakeFiles/Raytracer.dir/ImageGenerator.cpp.o: /home/cjsatnarine/Code/Raytracer/
 
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+
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+
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+
+/usr/include/c++/13/bits/shared_ptr_base.h:
+
+/usr/include/x86_64-linux-gnu/bits/pthreadtypes-arch.h:
+
+/usr/include/locale.h:
+
+/usr/include/c++/13/ext/aligned_buffer.h:
+
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+/usr/include/x86_64-linux-gnu/bits/fp-logb.h:
+
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+
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+/usr/include/x86_64-linux-gnu/bits/thread-shared-types.h:
+
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+
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+
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+
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+
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+
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+
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+
 /usr/include/x86_64-linux-gnu/bits/libc-header-start.h:
 
 /home/cjsatnarine/Code/Raytracer/material.h:
@@ -577,22 +631,12 @@ CMakeFiles/Raytracer.dir/ImageGenerator.cpp.o: /home/cjsatnarine/Code/Raytracer/
 
 /usr/include/c++/13/bits/stl_iterator.h:
 
-/usr/include/c++/13/string:
-
 /usr/include/asm-generic/errno.h:
 
 /usr/include/c++/13/bits/stl_iterator_base_funcs.h:
 
 /usr/include/c++/13/bits/stl_iterator_base_types.h:
 
-/usr/include/x86_64-linux-gnu/bits/types/error_t.h:
-
-/usr/include/x86_64-linux-gnu/bits/mathcalls-helper-functions.h:
-
-/home/cjsatnarine/Code/Raytracer/ray.h:
-
-/usr/include/c++/13/bits/stl_raw_storage_iter.h:
-
 /usr/include/x86_64-linux-gnu/bits/types/struct___jmp_buf_tag.h:
 
 /usr/include/c++/13/bits/stl_tempbuf.h:
@@ -635,10 +679,10 @@ CMakeFiles/Raytracer.dir/ImageGenerator.cpp.o: /home/cjsatnarine/Code/Raytracer/
 
 /usr/include/c++/13/bits/uses_allocator_args.h:
 
-/usr/include/c++/13/bits/stl_function.h:
-
 /usr/include/c++/13/tr1/beta_function.tcc:
 
+/usr/include/c++/13/bits/stl_function.h:
+
 /usr/include/c++/13/bits/utility.h:
 
 /home/cjsatnarine/Code/Raytracer/hittableList.h:
@@ -665,10 +709,6 @@ CMakeFiles/Raytracer.dir/ImageGenerator.cpp.o: /home/cjsatnarine/Code/Raytracer/
 
 /usr/include/c++/13/ostream:
 
-/usr/include/x86_64-linux-gnu/bits/types/struct_timespec.h:
-
-/usr/include/c++/13/cstddef:
-
 /usr/include/x86_64-linux-gnu/bits/types/struct_FILE.h:
 
 /usr/include/c++/13/bits/stl_pair.h:
@@ -683,7 +723,11 @@ CMakeFiles/Raytracer.dir/ImageGenerator.cpp.o: /home/cjsatnarine/Code/Raytracer/
 
 /usr/include/c++/13/debug/assertions.h:
 
-/usr/include/c++/13/ext/concurrence.h:
+/usr/include/c++/13/tr1/gamma.tcc:
+
+/usr/include/c++/13/cctype:
+
+/usr/include/c++/13/ext/atomicity.h:
 
 /usr/include/x86_64-linux-gnu/bits/types/sigset_t.h:
 
@@ -707,36 +751,16 @@ CMakeFiles/Raytracer.dir/ImageGenerator.cpp.o: /home/cjsatnarine/Code/Raytracer/
 
 /usr/include/c++/13/limits:
 
-/usr/include/c++/13/ext/alloc_traits.h:
-
-/usr/include/c++/13/new:
-
 /usr/include/x86_64-linux-gnu/c++/13/bits/gthr.h:
 
 /usr/include/c++/13/bits/basic_ios.tcc:
 
 /usr/include/c++/13/pstl/execution_defs.h:
 
+/usr/include/c++/13/ext/concurrence.h:
+
+/usr/include/c++/13/pstl/glue_algorithm_defs.h:
+
 /usr/include/x86_64-linux-gnu/bits/wordsize.h:
 
 /usr/include/c++/13/pstl/pstl_config.h:
-
-/usr/include/x86_64-linux-gnu/bits/thread-shared-types.h:
-
-/usr/include/c++/13/bits/range_access.h:
-
-/usr/include/c++/13/system_error:
-
-/usr/include/c++/13/bits/shared_ptr_base.h:
-
-/usr/include/c++/13/tr1/bessel_function.tcc:
-
-/usr/include/c++/13/tr1/exp_integral.tcc:
-
-/usr/include/c++/13/tr1/ell_integral.tcc:
-
-/usr/include/c++/13/cctype:
-
-/usr/include/c++/13/ext/atomicity.h:
-
-/usr/include/c++/13/tr1/gamma.tcc:

bvh.h

@@ -0,0 +1,76 @@
+#ifndef BVH_H
+#define BVH_H
+
+#include "aabb.h"
+#include <algorithm>
+#include "hittable.h"
+#include "hittableList.h"
+#include "rayTracer.h"
+
+class bvh_node : public hittable {
+  public:
+    bvh_node(hittableList list) : bvh_node(list.objects, 0, list.objects.size()) {
+        // This constructor (without span indices) creates an implicit copy of the hittable list, which we will modify. The lifetime of the copied list only extends until this constructor exits. 
+    }
+    
+    bvh_node(std::vector<shared_ptr<hittable>>& objects, size_t start, size_t end) {
+        int axis = randomInt(0,2);
+
+        auto comparator = (axis == 0) ? boxXCompare
+                        : (axis == 1) ? boxYCompare
+                                      : boxZCompare;
+
+        size_t object_span = end - start;
+
+        if (object_span == 1) {
+            left = right = objects[start];
+        } else if (object_span == 2) {
+            left = objects[start];
+            right = objects[start+1];
+        } else {
+            std::sort(objects.begin() + start, objects.begin() + end, comparator);
+
+            auto mid = start + object_span / 2;
+            left = make_shared<bvh_node>(objects, start, mid);
+            right = make_shared<bvh_node>(objects, mid, end);
+        }
+
+        bBox = aabb(left->boundingBox(), right->boundingBox());
+    }
+
+    bool hit(const ray& r, interval ray_t, hitRecord& rec) const override {
+        if (!bBox.hit(r, ray_t)) return false;
+
+        bool hitLeft = left->hit(r, ray_t, rec);
+        bool hitRight = right->hit(r, interval(ray_t.min, hitLeft ? rec.t : ray_t.max), rec);
+
+        return hitLeft || hitRight;
+    }
+
+    aabb boundingBox() const override { return bBox; }
+
+  private:
+    shared_ptr<hittable> left;
+    shared_ptr<hittable> right;
+    aabb bBox;
+
+    static bool boxCompare(const shared_ptr<hittable> a, const shared_ptr<hittable> b, int axisIndex) {
+        auto aAxisInterval = a->boundingBox().axisInterval(axisIndex);
+        auto bAxisInterval = b->boundingBox().axisInterval(axisIndex);
+        return aAxisInterval.min < bAxisInterval.min;
+    }
+
+    static bool boxXCompare(const shared_ptr<hittable> a, const shared_ptr<hittable> b) {
+        return boxCompare(a, b, 0);
+    }
+
+    static bool boxYCompare(const shared_ptr<hittable> a, const shared_ptr<hittable> b) {
+        return boxCompare(a, b, 1);
+    }
+
+    static bool boxZCompare(const shared_ptr<hittable> a, const shared_ptr<hittable> b) {
+        return boxCompare(a, b, 2);
+    }
+};
+
+#endif

hittable.h

@@ -2,6 +2,7 @@
 #define HITTABLE_H
 
 #include "rayTracer.h"
+#include "aabb.h"
 
 class material;
 
@@ -29,6 +30,8 @@ class hittable {
     virtual ~hittable() = default;
 
     virtual bool hit(const ray& r, interval rayT, hitRecord& rec) const = 0; 
+
+    virtual aabb boundingBox() const = 0;
 };
 
 #endif

hittableList.h

@@ -1,11 +1,15 @@
 #ifndef HITTABLE_LIST_H
 #define HITTABLE_LIST_H
 
+#include "aabb.h"
 #include "hittable.h"
 #include "rayTracer.h"
 #include <vector>
 
 class hittableList : public hittable {
+    private:
+        aabb bBox;
+
     public: 
         std::vector<shared_ptr<hittable>> objects;
 
@@ -20,6 +24,7 @@ class hittableList : public hittable {
 
         void add(shared_ptr<hittable> object) {
             objects.push_back(object);
+            bBox = aabb(bBox, object->boundingBox());
         }
 
         bool hit (const ray& r, interval rayT, hitRecord& rec) const override {
@@ -38,6 +43,10 @@ class hittableList : public hittable {
 
             return hitAnything;
         }
+
+        aabb boundingBox() const override { 
+            return bBox;
+        }
 };
 
 #endif

interval.h

@@ -12,6 +12,12 @@ class interval {
 
         interval(double min, double max) : min(min), max(max) {}
 
+        interval(const interval& a, const interval& b) {
+            // Create the interval tightly enclosing the two input intervals.
+            min = a.min <= b.min ? a.min : b.min;
+            max = a.max >= b.max ? a.max : b.max;
+        }
+
         double size() const {
             return max - min;
         }
@@ -30,6 +36,11 @@ class interval {
             return x;
         }
 
+        interval expand(double delta) const {
+            auto padding = delta / 2;
+            return interval(min - padding, max + padding);
+        }
+
         static const interval empty, universe;
 };
 

rayTracer.h

@@ -40,6 +40,11 @@ inline double randomDouble(double min, double max) {
     return min + (max - min) * randomDouble();
 }
 
+inline int randomInt(int min, int max) {
+    // Returns a random integer in [min, max].
+    return int(randomDouble(min, max++));
+}
+
 // Common headers. 
 #include "colour.h"
 #include "interval.h"

sphere.h

@@ -11,6 +11,7 @@ class sphere : public hittable {
         shared_ptr<material> mat;
         bool isMoving;
         vec3 centreVec;
+        aabb bBox;
 
         point3 sphereCentre(double time) const {
             // Linearly interpolate from centre1 to centre2 accoedingf to time, where t=0 yields centre1 and t=1 yields centre2. 
@@ -19,10 +20,18 @@ class sphere : public hittable {
 
     public: 
         // Stationary sphere. 
-        sphere(const point3& centre, double radius, shared_ptr<material> mat) : centre1(centre), radius(fmax(0, radius)), mat(mat), isMoving(false) {}
+        sphere(const point3& centre, double radius, shared_ptr<material> mat) : centre1(centre), radius(fmax(0, radius)), mat(mat), isMoving(false) {
+            auto rvec = vec3(radius, radius, radius);
+            bBox = aabb(centre1 - rvec, centre1 + rvec);
+        }
 
         // Moving sphere. 
         sphere(const point3& centre1, const point3& centre2, double radius, shared_ptr<material> mat) : centre1(centre1), radius(fmax(0, radius)), mat(mat), isMoving(true) {
+            auto rvec = vec3(radius, radius, radius);
+            aabb box1(centre1 - rvec, centre1 + rvec);
+            aabb box2(centre2 - rvec, centre2 + rvec);
+            bBox = aabb(box1, box2);
+            
             centreVec = centre2 - centre1;
         }
 
@@ -59,6 +68,10 @@ class sphere : public hittable {
             return true;
         }
 
+        aabb boundingBox() const override { 
+            return bBox; 
+        }
+
 };
 
 #endif