From 21112389350fa04881edd895ea6a5ba10bcd5eb0 Mon Sep 17 00:00:00 2001
From: Dynamitos <dynamitos15@gmail.com>
Date: Fri, 24 Jan 2025 19:23:58 +0100
Subject: [PATCH] implement box intersect

---
 src/scene/AABB.h  | 15 ++++++++++++---
 src/scene/BVH.cpp |  2 +-
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/src/scene/AABB.h b/src/scene/AABB.h
index e0f9c5a..18664f0 100644
--- a/src/scene/AABB.h
+++ b/src/scene/AABB.h
@@ -43,10 +43,19 @@ struct AABB
             max = glm::vec3(std::max(max.x, transformed.x), std::max(max.y, transformed.y), std::max(max.z, transformed.z));
         }
     }
-    bool intersects(Ray ray)
+    bool intersects(Ray ray, float tmin, float tmax)
     {
-        assert(false && "TODO");
-        return false;
+        glm::vec3 invD = 1.0f / ray.direction;
+        glm::vec3 t0s = glm::vec3(min - ray.origin) * invD;
+        glm::vec3 t1s = glm::vec3(max - ray.origin) * invD;
+
+        glm::vec3 tsmaller = std::min(t0s, t1s);
+        glm::vec3 tbigger = std::max(t0s, t1s);
+
+        tmin = std::max(tmin, std::max(tsmaller.x, std::max(tsmaller.y, tsmaller.z)));
+        tmax = std::min(tmax, std::min(tbigger.x, std::min(tbigger.y, tbigger.z)));
+
+        return (tmin < tmax);
     }
     static AABB combine(AABB lhs, AABB rhs)
     {
diff --git a/src/scene/BVH.cpp b/src/scene/BVH.cpp
index 68996d2..e754f9c 100644
--- a/src/scene/BVH.cpp
+++ b/src/scene/BVH.cpp
@@ -78,7 +78,7 @@ std::optional<IntersectionInfo> BVH::traceRay(Ray ray)
 
 std::vector<IntersectionInfo> BVH::generateIntersections(PNode& currentNode, Ray ray)
 {
-    if (!currentNode->aabb.intersects(ray))
+    if (!currentNode->aabb.intersects(ray, 0, 1))
     {
         return {};
     }