93 lines
3.1 KiB
C++
93 lines
3.1 KiB
C++
#ifndef SPHERE_H
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#define SPHERE_H
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#include "hittable.h"
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#include "rayTracer.h"
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class sphere : public hittable {
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private:
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point3 centre1;
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double radius;
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shared_ptr<material> mat;
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bool isMoving;
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vec3 centreVec;
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aabb bBox;
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point3 sphereCentre(double time) const {
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// Linearly interpolate from centre1 to centre2 accoedingf to time, where t=0 yields centre1 and t=1 yields centre2.
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return centre1 + time * centreVec;
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}
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static void getSphereUV(const point3& p, double & u, double& v) {
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// p: a given point on the sphere of radius one, centered at the origin.
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// u: returned value [0,1] of angle around the Y axis from X=-1.
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// v: returned value [0,1] of angle from Y=-1 to Y=+1.
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// <1 0 0> yields <0.50 0.50> <-1 0 0> yields <0.00 0.50>
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// <0 1 0> yields <0.50 1.00> < 0 -1 0> yields <0.50 0.00>
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// <0 0 1> yields <0.25 0.50> < 0 0 -1> yields <0.75 0.50>
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auto theta = acos(-p.y());
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auto phi = atan2(-p.z(), p.x()) + pi;
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u = phi / (2 * pi);
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v = theta / pi;
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}
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public:
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// Stationary sphere.
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sphere(const point3& centre, double radius, shared_ptr<material> mat) : centre1(centre), radius(fmax(0, radius)), mat(mat), isMoving(false) {
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auto rvec = vec3(radius, radius, radius);
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bBox = aabb(centre1 - rvec, centre1 + rvec);
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}
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// Moving sphere.
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sphere(const point3& centre1, const point3& centre2, double radius, shared_ptr<material> mat) : centre1(centre1), radius(fmax(0, radius)), mat(mat), isMoving(true) {
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auto rvec = vec3(radius, radius, radius);
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aabb box1(centre1 - rvec, centre1 + rvec);
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aabb box2(centre2 - rvec, centre2 + rvec);
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bBox = aabb(box1, box2);
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centreVec = centre2 - centre1;
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}
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bool hit(const ray& r, interval rayT, hitRecord& rec) const override {
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point3 centre = isMoving ? sphereCentre(r.time()) : centre1;
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vec3 oc = centre - r.origin();
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auto a = r.direction().lengthSquared();
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auto h = dot(r.direction(), oc);
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auto c = oc.lengthSquared() - radius * radius;
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auto discriminant = h * h - a * c;
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if (discriminant < 0) {
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return false;
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}
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auto sqtd = sqrt(discriminant);
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// Find the nearest root that lies in the acceptable range.
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auto root = (h - sqtd) / a;
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if (!rayT.surrounds(root)) {
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root = (h + sqtd) / a;
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if (!rayT.surrounds(root)) {
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return false;
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}
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}
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rec.t = root;
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rec.p = r.at(rec.t);
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vec3 outwardNormal = (rec.p - centre) / radius;
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rec.setFaceNormal(r, outwardNormal);
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getSphereUV(outwardNormal, rec.u, rec.v);
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rec.mat = mat;
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return true;
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}
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aabb boundingBox() const override {
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return bBox;
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}
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};
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#endif |