+double Body::Mass() const noexcept {
+ return mass;
+}
+
+void Body::Mass(double m) noexcept {
+ mass = m;
+}
+
+double Body::Radius() const noexcept {
+ return radius;
+}
+
+void Body::Radius(double r) noexcept {
+ radius = r;
+}
+
+double Body::SemiMajorAxis() const noexcept {
+ return sma;
+}
+
+void Body::SemiMajorAxis(double s) noexcept {
+ sma = s;
+}
+
+double Body::Eccentricity() const noexcept {
+ return ecc;
+}
+
+void Body::Eccentricity(double e) noexcept {
+ ecc = e;
+}
+
+double Body::Inclination() const noexcept {
+ return inc;
+}
+
+void Body::Inclination(double i) noexcept {
+ inc = i;
+}
+
+double Body::LongitudeAscending() const noexcept {
+ return asc;
+}
+
+void Body::LongitudeAscending(double l) noexcept {
+ asc = l;
+}
+
+double Body::ArgumentPeriapsis() const noexcept {
+ return arg;
+}
+
+void Body::ArgumentPeriapsis(double a) noexcept {
+ arg = a;
+}
+
+double Body::MeanAnomaly() const noexcept {
+ return mna;
+}
+
+void Body::MeanAnomaly(double m) noexcept {
+ mna = m;
+}
+
+double Body::GravitationalParameter() const noexcept {
+ return G * Mass();
+}
+
+double Body::OrbitalPeriod() const noexcept {
+ if (parent) {
+ return PI_2p0 * sqrt((sma * sma * sma) / (G * (parent->Mass() + Mass())));
+ } else {
+ return 0.0;
+ }
+}
+
+glm::mat4 Body::ToParent() const noexcept {
+ if (!parent) {
+ return glm::mat4(1.0f);
+ }
+
+ double T = OrbitalPeriod();
+
+ double M = mna + PI_2p0 * (GetSimulation().Time() / T); // + time
+
+ double E = M; // eccentric anomaly, solve M = E - e sin E
+ while (true) {
+ double dE = (E - ecc * sin(E) - M) / (1 - ecc * cos(E));
+ E -= dE;
+ if (abs(dE) < 1.0e-6) break;
+ }
+
+ // coordinates in orbital plane
+ double P = sma * (cos(E) - ecc);
+ double Q = sma * sin(E) * sqrt(1 - (ecc * ecc));
+
+ // tile by argument of periapsis, …
+ double x = cos(arg) * P - sin(arg) * Q;
+ double y = sin(arg) * P + cos(arg) * Q;
+ // …inclination, …
+ double z = sin(inc) * x;
+ x = cos(inc) * x;
+ // …and longitude of ascending node
+ glm::vec3 pos(
+ cos(asc) * x - sin(asc) * y,
+ sin(asc) * x + cos(asc) * y,
+ z);
+
+ // TODO: calculate complete matrix
+ return glm::translate(-pos);
+}
+
+glm::mat4 Body::FromParent() const noexcept {
+ if (!parent) {
+ return glm::mat4(1.0f);
+ }
+ // TODO: calculate real position
+ return glm::translate(glm::vec3(-sma, 0.0f, 0.0f));
+}
+