From e4e2d26a16c7fe24a20d4609a05dc51815ed29dd Mon Sep 17 00:00:00 2001
From: vonhyou <moi@rfung.dev>
Date: Mon, 19 Feb 2024 14:18:22 -0500
Subject: [PATCH] add ray constructor

---
 src/Geometry.cc  |  9 ++++++++-
 src/RayTracer.cc | 16 +++++++++++++++-
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/src/Geometry.cc b/src/Geometry.cc
index 379ecaa..93c6241 100644
--- a/src/Geometry.cc
+++ b/src/Geometry.cc
@@ -4,6 +4,13 @@ void Geometry::setTransform(const Matrix4f &transform) {
   this->transform = transform;
 }
 
-bool Sphere::intersect(const Ray &r) const { return false; }
+bool Sphere::intersect(const Ray &r) const {
+  Vector3f originCenter = r.getOrigin() - center;
+  int a = r.getDirection().dot(r.getDirection());
+  int b = 2 * originCenter.dot(r.getDirection());
+  int c = originCenter.dot(originCenter) - radius * radius;
+
+  return b * b - 4 * a * c >= 0;
+}
 
 bool Rectangle::intersect(const Ray &r) const { return false; }
diff --git a/src/RayTracer.cc b/src/RayTracer.cc
index 0515d1a..d75cca2 100644
--- a/src/RayTracer.cc
+++ b/src/RayTracer.cc
@@ -2,6 +2,7 @@
 #include "../external/simpleppm.h"
 #include "Parser.h"
 #include "Ray.h"
+#include <Eigen/src/Core/Matrix.h>
 
 void RayTracer::parse() {
   for (auto i = json["output"].begin(); i != json["output"].end(); ++i)
@@ -17,7 +18,20 @@ void RayTracer::parse() {
 Ray getRay(int x, int y, const Vector3f &camPos, const Vector3f &lookat,
            float fov, int width, int height) {
   // TODO: compute ray
-  return Ray(Vector3f(), Vector3f());
+  float viewportHeight = 2.0f;
+  float viewportWidth = viewportHeight * width / height;
+  Vector3f viewportU = Vector3f(viewportWidth, 0, 0);
+  Vector3f viewportV = Vector3f(0, -viewportHeight, 0);
+
+  Vector3f deltaU = viewportU / width;
+  Vector3f deltaV = viewportV / height;
+
+  Vector3f viewportUpperLeft = camPos - lookat - viewportU / 2 - viewportV / 2;
+  Vector3f pixelUpperLeftPos = viewportUpperLeft + 0.5 * (deltaU + deltaV);
+
+  Vector3f pixelCenter = pixelUpperLeftPos + (x * deltaU) + (y * deltaV);
+
+  return Ray(camPos, pixelCenter - camPos);
 }
 
 void RayTracer::render(Scene *scene) {