From 4d5f0973c6a0ee75fc335038df04c3afbfb7c6cb Mon Sep 17 00:00:00 2001
From: Zach <duong.nguyen@rochester.edu>
Date: Mon, 5 Feb 2024 14:04:03 -0500
Subject: [PATCH] [bvh]: add an AABB class

---
 CMakeLists.txt            |  1 +
 include/3d/AABB.cuh       | 20 +++++++++++++
 include/math/Interval.cuh | 20 ++++++-------
 include/math/Vec3.cuh     |  1 +
 src/3d/AABB.cu            | 63 +++++++++++++++++++++++++++++++++++++++
 src/math/Vec3.cu          |  9 ++++++
 6 files changed, 104 insertions(+), 10 deletions(-)
 create mode 100644 include/3d/AABB.cuh
 create mode 100644 src/3d/AABB.cu

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 70a9f9a..a75aebd 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -16,6 +16,7 @@ set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 set(LIBRARY_SOURCE_DIR ${CMAKE_SOURCE_DIR}/src)
 
 set(LIBRARY_SOURCES
+    ${LIBRARY_SOURCE_DIR}/3d/AABB.cu
     ${LIBRARY_SOURCE_DIR}/3d/Camera.cu
     ${LIBRARY_SOURCE_DIR}/3d/Material.cu
     ${LIBRARY_SOURCE_DIR}/3d/Object.cu
diff --git a/include/3d/AABB.cuh b/include/3d/AABB.cuh
new file mode 100644
index 0000000..6cc3431
--- /dev/null
+++ b/include/3d/AABB.cuh
@@ -0,0 +1,20 @@
+#ifndef AABB_H
+#define AABB_H
+
+#include "Interval.cuh"
+#include "Ray.cuh"
+#include "Vec3.cuh"
+
+class AABB {
+public:
+  Interval x, y, z;
+
+  __device__ AABB();
+  __device__ AABB(const Interval &_x, const Interval &_y, const Interval &_z);
+  __device__ AABB(const Point3 &a, const Point3 &b);
+
+  __device__ const Interval &axis(int i) const;
+  __device__ bool hit(const Ray &r, Interval ray_t) const;
+};
+
+#endif // AABB_H
\ No newline at end of file
diff --git a/include/math/Interval.cuh b/include/math/Interval.cuh
index 2ad7a80..4b7860a 100644
--- a/include/math/Interval.cuh
+++ b/include/math/Interval.cuh
@@ -5,27 +5,27 @@
 
 class Interval {
 public:
-  float _min;
-  float _max;
+  float min;
+  float max;
 
-  __host__ __device__ Interval() : _min(+infinity), _max(-infinity) {}
+  __host__ __device__ Interval() : min(+infinity), max(-infinity) {}
 
-  __host__ __device__ Interval(float min, float max) : _min(min), _max(max) {}
+  __host__ __device__ Interval(float min, float max) : min(min), max(max) {}
 
   __host__ __device__ bool contains(float x) const {
-    return _min <= x && x <= _max;
+    return min <= x && x <= max;
   }
 
   __host__ __device__ bool surrounds(float x) const {
-    return _min < x && x < _max;
+    return min < x && x < max;
   }
 
   __host__ __device__ float clamp(float x) const {
-    if (x < _min)
-      return _min;
+    if (x < min)
+      return min;
 
-    if (x > _max)
-      return _max;
+    if (x > max)
+      return max;
 
     return x;
   }
diff --git a/include/math/Vec3.cuh b/include/math/Vec3.cuh
index 54623c9..fde4e84 100644
--- a/include/math/Vec3.cuh
+++ b/include/math/Vec3.cuh
@@ -19,6 +19,7 @@ public:
   __device__ Vec3(float x, float y, float z);
 
   __device__ void set(float x, float y, float z);
+  __device__ float get(int i) const;
 
   __device__ float length() const;
   __device__ float lengthSquared() const;
diff --git a/src/3d/AABB.cu b/src/3d/AABB.cu
new file mode 100644
index 0000000..fa6f80b
--- /dev/null
+++ b/src/3d/AABB.cu
@@ -0,0 +1,63 @@
+#include "AABB.cuh"
+#include "Interval.cuh"
+#include "Vec3.cuh"
+
+__device__ AABB::AABB() {}
+__device__ AABB::AABB(const Interval &_x, const Interval &_y,
+                      const Interval &_z)
+    : x(_x), y(_y), z(_z) {}
+__device__ AABB::AABB(const Point3 &a, const Point3 &b) {
+  x = Interval(fmin(a.x, b.x), fmax(a.x, b.x));
+  y = Interval(fmin(a.y, b.y), fmax(a.y, b.y));
+  z = Interval(fmin(a.z, b.z), fmax(a.z, b.z));
+}
+
+__device__ const Interval &AABB::axis(int i) const {
+  if (i == 0)
+    return x;
+  if (i == 1)
+    return y;
+  /* else */ return z;
+}
+
+__device__ bool AABB::hit(const Ray &r, Interval ray_t) const {
+  // for (int a = 0; a < 3; a++) {
+  //   auto t0 = fmin((axis(a).min - r.origin.get(a)) / r.direction.get(a),
+  //                  (axis(a).max - r.origin.get(a)) / r.direction.get(a));
+  //   auto t1 = fmax((axis(a).min - r.origin.get(a)) / r.direction.get(a),
+  //                  (axis(a).max - r.origin.get(a)) / r.direction.get(a));
+
+  //   ray_t.min = fmax(t0, ray_t.min);
+  //   ray_t.max = fmin(t1, ray_t.max);
+
+  //   if (ray_t.max <= ray_t.min)
+  //     return false;
+
+  //   return true;
+  // }
+
+  for (int a = 0; a < 3; a++) {
+    float inverseDirection = 1.0f / r.direction.get(a);
+    float origin = r.origin.get(a);
+
+    float t0 = (axis(a).min - origin) * inverseDirection;
+    float t1 = (axis(a).max - origin) * inverseDirection;
+
+    if (inverseDirection < 0) {
+      float temp = t0;
+      t0 = t1;
+      t1 = temp;
+    }
+
+    if (t0 > ray_t.min)
+      ray_t.min = t0;
+    if (t1 < ray_t.max)
+      ray_t.max = t1;
+
+    if (ray_t.max <= ray_t.min) {
+      return false;
+    }
+  }
+
+  return true;
+}
\ No newline at end of file
diff --git a/src/math/Vec3.cu b/src/math/Vec3.cu
index 8bf024f..9b4d589 100644
--- a/src/math/Vec3.cu
+++ b/src/math/Vec3.cu
@@ -5,6 +5,15 @@
 __device__ Vec3::Vec3() : x(0), y(0), z(0) {}
 __device__ Vec3::Vec3(float x, float y, float z) : x(x), y(y), z(z) {}
 
+__device__ float Vec3::get(int i) const {
+  if (i == 0) {
+    return x;
+  }
+  if (i == 1) {
+    return y;
+  }
+  /* else */ return z;
+}
 __device__ void Vec3::set(float x, float y, float z) {
   this->x = x;
   this->y = y;