ray-tracer-comp371/src/Geometry.cc

#include "Geometry.h"

#include <Eigen/Dense>

void Geometry::setTransform(const Matrix4f &transform) {
  this->transform = transform;
}

bool Sphere::intersect(const Ray &r) const {
  Vector3f originCenter = r.getOrigin() - center;
  float a = r.getDirection().dot(r.getDirection());
  float b = 2.0f * originCenter.dot(r.getDirection());
  float c = originCenter.dot(originCenter) - radius * radius;

  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 denom = normal.dot(r.getDirection());
  if (abs(denom) < 1e-6f)
    return false;

  float t = -normal.dot(r.getOrigin() - p1) / denom;
  if (t <= 0)
    return false;

  Vector3f p = r.getOrigin() + t * r.getDirection();

  return isInRectangle(p, p1, p2, p3, p4, normal);
}