From 0633159427fd34f647cfa9593f2564d94b3a1bfa Mon Sep 17 00:00:00 2001
From: vonhyou <moi@rfung.dev>
Date: Wed, 21 Feb 2024 01:33:06 -0500
Subject: [PATCH] finish ray casting

---
 src/Geometry.cc  | 17 ++++++++++++++---
 src/RayTracer.cc |  6 +++---
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/src/Geometry.cc b/src/Geometry.cc
index f78b14c..9a98549 100644
--- a/src/Geometry.cc
+++ b/src/Geometry.cc
@@ -15,18 +15,29 @@ bool Sphere::intersect(const Ray &r) const {
   return b * b - 4 * a * c >= 0;
 }
 
+bool isInRectangle(const Vector3f &p, const Vector3f &a, const Vector3f &b,
+                   const Vector3f &c, const Vector3f &d, const Vector3f &n) {
+  float s1 = (b - a).cross(p - a).dot(n);
+  float s2 = (c - b).cross(p - b).dot(n);
+  float s3 = (d - c).cross(p - c).dot(n);
+  float s4 = (a - d).cross(p - d).dot(n);
+
+  return (s1 >= 0 && s2 >= 0 && s3 >= 0 && s4 >= 0) ||
+         (s1 <= 0 && s2 <= 0 && s3 <= 0 && s4 <= 0);
+}
+
 bool Rectangle::intersect(const Ray &r) const {
   Vector3f normal = (p2 - p1).cross(p3 - p1).normalized();
-  float d = normal.dot(p1);
 
   float denom = normal.dot(r.getDirection());
   if (abs(denom) < 1e-6f)
     return false;
 
-  float t = (normal.dot(r.getOrigin() - p1) - d) / denom;
+  float t = -normal.dot(r.getOrigin() - p1) / denom;
   if (t <= 0)
     return false;
 
   Vector3f p = r.getOrigin() + t * r.getDirection();
-  return true;
+
+  return isInRectangle(p, p1, p2, p3, p4, normal);
 }
diff --git a/src/RayTracer.cc b/src/RayTracer.cc
index 1c3cb39..e9c93a1 100644
--- a/src/RayTracer.cc
+++ b/src/RayTracer.cc
@@ -31,12 +31,12 @@ void RayTracer::render(Scene *scene) {
   Vector3f up = scene->getUpVector();
   float vpHeight = 2 * tan(fov / 180 * M_PI / 2) * lookAt.norm();
   float vpWidth = vpHeight * width / height;
-  Vector3f vpU = Vector3f(-vpWidth, 0, 0);
-  Vector3f vpV = Vector3f(0, vpHeight, 0);
+  Vector3f vpU = Vector3f(vpWidth, 0, 0);
+  Vector3f vpV = Vector3f(0, -vpHeight, 0);
   Vector3f du = vpU / width;
   Vector3f dv = vpV / height;
 
-  Vector3f vpUpperLeft = cameraPos - lookAt - vpU / 2.0 - vpV / 2.0;
+  Vector3f vpUpperLeft = cameraPos + lookAt - vpU / 2.0 - vpV / 2.0;
   Vector3f pxUpperLeft = vpUpperLeft + (du + dv) / 2.0;
 
   Buffer buffer(width * height * 3);