From e78b5392586442dcda2d290b73f8377c9261423e Mon Sep 17 00:00:00 2001
From: Jean-Michel Gorius <jean-michel.gorius@protonmail.com>
Date: Sun, 13 Nov 2022 18:25:33 +0100
Subject: [PATCH] Add box hittables

---
 hittable.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 hittable.h | 10 ++++++++++
 main.c     | 13 ++++++++++++-
 3 files changed, 69 insertions(+), 1 deletion(-)

diff --git a/hittable.c b/hittable.c
index 1cf6b9d..fc5a1a7 100644
--- a/hittable.c
+++ b/hittable.c
@@ -161,6 +161,39 @@ Hittable *hittable_create_yz_rectangle(double y0, double y1, double z0,
   return result;
 }
 
+Hittable *hittable_create_box(Point3 p0, Point3 p1, const Material *material,
+                              Arena *arena) {
+  Hittable *result = arena_alloc(arena, sizeof(Hittable));
+  result->type = HITTABLE_BOX;
+  result->box.min = p0;
+  result->box.max = p1;
+  hittable_list_add(&result->box.sides,
+                    hittable_create_xy_rectangle(p0.x, p1.x, p0.y, p1.y, p0.z,
+                                                 material, arena),
+                    arena);
+  hittable_list_add(&result->box.sides,
+                    hittable_create_xy_rectangle(p0.x, p1.x, p0.y, p1.y, p1.z,
+                                                 material, arena),
+                    arena);
+  hittable_list_add(&result->box.sides,
+                    hittable_create_xz_rectangle(p0.x, p1.x, p0.z, p1.z, p0.y,
+                                                 material, arena),
+                    arena);
+  hittable_list_add(&result->box.sides,
+                    hittable_create_xz_rectangle(p0.x, p1.x, p0.z, p1.z, p1.y,
+                                                 material, arena),
+                    arena);
+  hittable_list_add(&result->box.sides,
+                    hittable_create_yz_rectangle(p0.y, p1.y, p0.z, p1.z, p0.x,
+                                                 material, arena),
+                    arena);
+  hittable_list_add(&result->box.sides,
+                    hittable_create_yz_rectangle(p0.y, p1.y, p0.z, p1.z, p1.x,
+                                                 material, arena),
+                    arena);
+  return result;
+}
+
 static bool hittable_list_hit(const HittableList *list, Ray r, double t_min,
                               double t_max, HitRecord *record) {
   bool hit_anything = false;
@@ -329,6 +362,11 @@ static bool yz_rectangle_hit(const YZRectangle *rectangle, Ray r, double t_min,
   return true;
 }
 
+static bool box_hit(const Box *box, Ray r, double t_min, double t_max,
+                    HitRecord *record) {
+  return hittable_list_hit(&box->sides, r, t_min, t_max, record);
+}
+
 bool hittable_hit(const Hittable *hittable, Ray r, double t_min, double t_max,
                   HitRecord *record) {
   switch (hittable->type) {
@@ -346,6 +384,8 @@ bool hittable_hit(const Hittable *hittable, Ray r, double t_min, double t_max,
     return xz_rectangle_hit(&hittable->xz_rectangle, r, t_min, t_max, record);
   case HITTABLE_YZ_RECTANGLE:
     return yz_rectangle_hit(&hittable->yz_rectangle, r, t_min, t_max, record);
+  case HITTABLE_BOX:
+    return box_hit(&hittable->box, r, t_min, t_max, record);
   }
   return false;
 }
@@ -437,6 +477,11 @@ static bool yz_rectangle_bounding_box(const YZRectangle *rectangle,
   return true;
 }
 
+static bool box_bounding_box(const Box *box, AABB *bounding_box) {
+  *bounding_box = (AABB){box->min, box->max};
+  return true;
+}
+
 bool hittable_bounding_box(const Hittable *hittable, double time_start,
                            double time_end, AABB *bounding_box) {
   switch (hittable->type) {
@@ -456,6 +501,8 @@ bool hittable_bounding_box(const Hittable *hittable, double time_start,
     return xz_rectangle_bounding_box(&hittable->xz_rectangle, bounding_box);
   case HITTABLE_YZ_RECTANGLE:
     return yz_rectangle_bounding_box(&hittable->yz_rectangle, bounding_box);
+  case HITTABLE_BOX:
+    return box_bounding_box(&hittable->box, bounding_box);
   }
   return false;
 }
diff --git a/hittable.h b/hittable.h
index 644f9dd..84f7d00 100644
--- a/hittable.h
+++ b/hittable.h
@@ -30,6 +30,7 @@ typedef enum HittableType {
   HITTABLE_XY_RECTANGLE,
   HITTABLE_XZ_RECTANGLE,
   HITTABLE_YZ_RECTANGLE,
+  HITTABLE_BOX,
 } HittableType;
 
 typedef struct Hittable Hittable;
@@ -74,6 +75,12 @@ typedef struct YZRectangle {
   double y0, y1, z0, z1, k;
 } YZRectangle;
 
+typedef struct Box {
+  HittableList sides;
+  Point3 min;
+  Point3 max;
+} Box;
+
 struct Hittable {
   HittableType type;
   union {
@@ -84,6 +91,7 @@ struct Hittable {
     XYRectangle xy_rectangle;
     XZRectangle xz_rectangle;
     YZRectangle yz_rectangle;
+    Box box;
   };
 };
 
@@ -105,6 +113,8 @@ Hittable *hittable_create_xz_rectangle(double x0, double x1, double z0,
 Hittable *hittable_create_yz_rectangle(double y0, double y1, double z0,
                                        double z1, double k,
                                        const Material *material, Arena *arena);
+Hittable *hittable_create_box(Point3 p0, Point3 p1, const Material *material,
+                              Arena *arena);
 
 bool hittable_hit(const Hittable *hittable, Ray r, double t_min, double t_max,
                   HitRecord *record);
diff --git a/main.c b/main.c
index 647b3a3..2a7f73e 100644
--- a/main.c
+++ b/main.c
@@ -219,7 +219,18 @@ static Hittable *cornell_box(Arena *arena) {
       &world->list,
       hittable_create_xy_rectangle(0, 555, 0, 555, 555, white, arena), arena);
 
-  return world;
+  hittable_list_add(&world->list,
+                    hittable_create_box((Point3){130, 0, 65},
+                                        (Point3){295, 165, 230}, white, arena),
+                    arena);
+  hittable_list_add(&world->list,
+                    hittable_create_box((Point3){265, 0, 295},
+                                        (Point3){430, 330, 460}, white, arena),
+                    arena);
+
+  Hittable *bvh_root = hittable_create_bvh_node(
+      world->list.objects, 0, world->list.size, 0.0, 1.0, arena);
+  return bvh_root;
 }
 
 int main(int argc, char *argv[]) {