External/HIP/workload/ray-tracing/InOneWeekend/sphere.h

#ifndef SPHERE_H
#define SPHERE_H
//==============================================================================================
// Originally written in 2016 by Peter Shirley <ptrshrl@gmail.com>
//
// To the extent possible under law, the author(s) have dedicated all copyright
// and related and neighboring rights to this software to the public domain
// worldwide. This software is distributed without any warranty.
//
// You should have received a copy (see file COPYING.txt) of the CC0 Public
// Domain Dedication along with this software. If not, see
// <http://creativecommons.org/publicdomain/zero/1.0/>.
//
// The original source code is from
//    https://github.com/RayTracing/raytracing.github.io/tree/release/src/InOneWeekend
//
// Changes to the original code follow the following license.
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//==============================================================================================

#include "rtweekend.h"

#include "hittable.h"

class sphere : public hittable {
public:
  __host__ __device__ sphere(point3 _center, double _radius,
                             SharedPtr<material> _material)
      : center(_center), radius(_radius), mat(_material) {}

  __host__ __device__ bool hit(const ray &r, interval ray_t,
                               hit_record &rec) const override {
    vec3 oc = r.origin() - center;
    auto a = r.direction().length_squared();
    auto half_b = dot(oc, r.direction());
    auto c = oc.length_squared() - radius * radius;

    auto discriminant = half_b * half_b - a * c;
    if (discriminant < 0)
      return false;

    // Find the nearest root that lies in the acceptable range.
    auto sqrtd = sqrt(discriminant);
    auto root = (-half_b - sqrtd) / a;
    if (!ray_t.surrounds(root)) {
      root = (-half_b + sqrtd) / a;
      if (!ray_t.surrounds(root))
        return false;
    }

    rec.t = root;
    rec.p = r.at(rec.t);
    vec3 outward_normal = (rec.p - center) / radius;
    rec.set_face_normal(r, outward_normal);
    rec.mat = mat;

    return true;
  }

private:
  point3 center;
  double radius;
  SharedPtr<material> mat;
};

#endif