Use YXZ convention for Euler angles.
As discussed in issues #1479 and #9782, choosing the up axis (which is Y in Godot) as the axis of the last (or first) rotation is helpful in practical use cases. This also aligns Godot's convention with Unity, helping with a smoother transition for people who are used to working with Unity (issue #9905). Internally, both XYZ and YXZ functions are kept, for potential future applications.
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@ -338,7 +338,7 @@ void Basis::set_rotation_axis_angle(const Vector3 &p_axis, real_t p_angle) {
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rotate(p_axis, p_angle);
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}
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// get_euler returns a vector containing the Euler angles in the format
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// get_euler_xyz returns a vector containing the Euler angles in the format
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// (a1,a2,a3), where a3 is the angle of the first rotation, and a1 is the last
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// (following the convention they are commonly defined in the literature).
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//
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@ -348,7 +348,7 @@ void Basis::set_rotation_axis_angle(const Vector3 &p_axis, real_t p_angle) {
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// And thus, assuming the matrix is a rotation matrix, this function returns
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// the angles in the decomposition R = X(a1).Y(a2).Z(a3) where Z(a) rotates
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// around the z-axis by a and so on.
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Vector3 Basis::get_euler() const {
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Vector3 Basis::get_euler_xyz() const {
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// Euler angles in XYZ convention.
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// See https://en.wikipedia.org/wiki/Euler_angles#Rotation_matrix
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@ -366,6 +366,9 @@ Vector3 Basis::get_euler() const {
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if (euler.y > -Math_PI * 0.5) {
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//if rotation is Y-only, return a proper -pi,pi range like in x or z for the same case.
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if (elements[1][0] == 0.0 && elements[0][1] == 0.0 && elements[0][0] < 0.0) {
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euler.x = 0;
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euler.z = 0;
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if (euler.y > 0.0)
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euler.y = Math_PI - euler.y;
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else
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@ -389,10 +392,11 @@ Vector3 Basis::get_euler() const {
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return euler;
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}
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// set_euler expects a vector containing the Euler angles in the format
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// (c,b,a), where a is the angle of the first rotation, and c is the last.
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// set_euler_xyz expects a vector containing the Euler angles in the format
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// (ax,ay,az), where ax is the angle of rotation around x axis,
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// and similar for other axes.
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// The current implementation uses XYZ convention (Z is the first rotation).
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void Basis::set_euler(const Vector3 &p_euler) {
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void Basis::set_euler_xyz(const Vector3 &p_euler) {
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real_t c, s;
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@ -412,6 +416,78 @@ void Basis::set_euler(const Vector3 &p_euler) {
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*this = xmat * (ymat * zmat);
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}
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// get_euler_yxz returns a vector containing the Euler angles in the YXZ convention,
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// as in first-Z, then-X, last-Y. The angles for X, Y, and Z rotations are returned
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// as the x, y, and z components of a Vector3 respectively.
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Vector3 Basis::get_euler_yxz() const {
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// Euler angles in YXZ convention.
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// See https://en.wikipedia.org/wiki/Euler_angles#Rotation_matrix
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//
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// rot = cy*cz+sy*sx*sz cz*sy*sx-cy*sz cx*sy
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// cx*sz cx*cz -sx
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// cy*sx*sz-cz*sy cy*cz*sx+sy*sz cy*cx
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Vector3 euler;
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#ifdef MATH_CHECKS
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ERR_FAIL_COND_V(is_rotation() == false, euler);
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#endif
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real_t m12 = elements[1][2];
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if (m12 < 1) {
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if (m12 > -1) {
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if (elements[1][0] == 0 && elements[0][1] == 0 && elements[2][2] < 0) { // use pure x rotation
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real_t x = asin(-m12);
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euler.y = 0;
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euler.z = 0;
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if (x > 0.0)
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euler.x = Math_PI - x;
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else
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euler.x = -(Math_PI + x);
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} else {
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euler.x = asin(-m12);
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euler.y = atan2(elements[0][2], elements[2][2]);
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euler.z = atan2(elements[1][0], elements[1][1]);
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}
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} else { // m12 == -1
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euler.x = Math_PI * 0.5;
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euler.y = -atan2(-elements[0][1], elements[0][0]);
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euler.z = 0;
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}
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} else { // m12 == 1
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euler.x = -Math_PI * 0.5;
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euler.y = -atan2(-elements[0][1], elements[0][0]);
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euler.z = 0;
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}
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return euler;
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}
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// set_euler_yxz expects a vector containing the Euler angles in the format
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// (ax,ay,az), where ax is the angle of rotation around x axis,
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// and similar for other axes.
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// The current implementation uses YXZ convention (Z is the first rotation).
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void Basis::set_euler_yxz(const Vector3 &p_euler) {
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real_t c, s;
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c = Math::cos(p_euler.x);
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s = Math::sin(p_euler.x);
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Basis xmat(1.0, 0.0, 0.0, 0.0, c, -s, 0.0, s, c);
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c = Math::cos(p_euler.y);
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s = Math::sin(p_euler.y);
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Basis ymat(c, 0.0, s, 0.0, 1.0, 0.0, -s, 0.0, c);
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c = Math::cos(p_euler.z);
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s = Math::sin(p_euler.z);
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Basis zmat(c, -s, 0.0, s, c, 0.0, 0.0, 0.0, 1.0);
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//optimizer will optimize away all this anyway
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*this = ymat * xmat * zmat;
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}
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bool Basis::is_equal_approx(const Basis &a, const Basis &b) const {
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for (int i = 0; i < 3; i++) {
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@ -84,8 +84,13 @@ public:
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void set_rotation_euler(const Vector3 &p_euler);
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void set_rotation_axis_angle(const Vector3 &p_axis, real_t p_angle);
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Vector3 get_euler() const;
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void set_euler(const Vector3 &p_euler);
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Vector3 get_euler_xyz() const;
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void set_euler_xyz(const Vector3 &p_euler);
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Vector3 get_euler_yxz() const;
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void set_euler_yxz(const Vector3 &p_euler);
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Vector3 get_euler() const { return get_euler_yxz(); };
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void set_euler(const Vector3 &p_euler) { set_euler_yxz(p_euler); };
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void get_axis_angle(Vector3 &r_axis, real_t &r_angle) const;
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void set_axis_angle(const Vector3 &p_axis, real_t p_phi);
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@ -31,10 +31,11 @@
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#include "matrix3.h"
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#include "print_string.h"
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// set_euler expects a vector containing the Euler angles in the format
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// (c,b,a), where a is the angle of the first rotation, and c is the last.
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// The current implementation uses XYZ convention (Z is the first rotation).
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void Quat::set_euler(const Vector3 &p_euler) {
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// set_euler_xyz expects a vector containing the Euler angles in the format
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// (ax,ay,az), where ax is the angle of rotation around x axis,
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// and similar for other axes.
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// This implementation uses XYZ convention (Z is the first rotation).
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void Quat::set_euler_xyz(const Vector3 &p_euler) {
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real_t half_a1 = p_euler.x * 0.5;
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real_t half_a2 = p_euler.y * 0.5;
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real_t half_a3 = p_euler.z * 0.5;
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@ -56,12 +57,48 @@ void Quat::set_euler(const Vector3 &p_euler) {
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-sin_a1 * sin_a2 * sin_a3 + cos_a1 * cos_a2 * cos_a3);
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}
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// get_euler returns a vector containing the Euler angles in the format
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// (a1,a2,a3), where a3 is the angle of the first rotation, and a1 is the last.
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// The current implementation uses XYZ convention (Z is the first rotation).
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Vector3 Quat::get_euler() const {
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// get_euler_xyz returns a vector containing the Euler angles in the format
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// (ax,ay,az), where ax is the angle of rotation around x axis,
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// and similar for other axes.
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// This implementation uses XYZ convention (Z is the first rotation).
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Vector3 Quat::get_euler_xyz() const {
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Basis m(*this);
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return m.get_euler();
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return m.get_euler_xyz();
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}
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// set_euler_yxz expects a vector containing the Euler angles in the format
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// (ax,ay,az), where ax is the angle of rotation around x axis,
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// and similar for other axes.
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// This implementation uses YXZ convention (Z is the first rotation).
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void Quat::set_euler_yxz(const Vector3 &p_euler) {
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real_t half_a1 = p_euler.y * 0.5;
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real_t half_a2 = p_euler.x * 0.5;
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real_t half_a3 = p_euler.z * 0.5;
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// R = Y(a1).X(a2).Z(a3) convention for Euler angles.
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// Conversion to quaternion as listed in https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19770024290.pdf (page A-6)
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// a3 is the angle of the first rotation, following the notation in this reference.
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real_t cos_a1 = Math::cos(half_a1);
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real_t sin_a1 = Math::sin(half_a1);
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real_t cos_a2 = Math::cos(half_a2);
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real_t sin_a2 = Math::sin(half_a2);
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real_t cos_a3 = Math::cos(half_a3);
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real_t sin_a3 = Math::sin(half_a3);
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set(sin_a1 * cos_a2 * sin_a3 + cos_a1 * sin_a2 * cos_a3,
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sin_a1 * cos_a2 * cos_a3 - cos_a1 * sin_a2 * sin_a3,
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-sin_a1 * sin_a2 * cos_a3 + cos_a1 * sin_a2 * sin_a3,
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sin_a1 * sin_a2 * sin_a3 + cos_a1 * cos_a2 * cos_a3);
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}
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// get_euler_yxz returns a vector containing the Euler angles in the format
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// (ax,ay,az), where ax is the angle of rotation around x axis,
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// and similar for other axes.
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// This implementation uses YXZ convention (Z is the first rotation).
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Vector3 Quat::get_euler_yxz() const {
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Basis m(*this);
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return m.get_euler_yxz();
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}
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void Quat::operator*=(const Quat &q) {
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@ -51,8 +51,15 @@ public:
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bool is_normalized() const;
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Quat inverse() const;
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_FORCE_INLINE_ real_t dot(const Quat &q) const;
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void set_euler(const Vector3 &p_euler);
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Vector3 get_euler() const;
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void set_euler_xyz(const Vector3 &p_euler);
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Vector3 get_euler_xyz() const;
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void set_euler_yxz(const Vector3 &p_euler);
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Vector3 get_euler_yxz() const;
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void set_euler(const Vector3 &p_euler) { set_euler_yxz(p_euler); };
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Vector3 get_euler() const { return get_euler_yxz(); };
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Quat slerp(const Quat &q, const real_t &t) const;
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Quat slerpni(const Quat &q, const real_t &t) const;
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Quat cubic_slerp(const Quat &q, const Quat &prep, const Quat &postq, const real_t &t) const;
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@ -7652,7 +7652,7 @@
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<argument index="0" name="euler" type="Vector3">
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</argument>
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<description>
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Create a rotation matrix (in the XYZ convention: first Z, then Y, and X last) from the specified Euler angles, given in the vector format as (third, second, first).
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Create a rotation matrix (in the YXZ convention: first Z, then X, and Y last) from the specified Euler angles, given in the vector format as (X-angle, Y-angle, Z-angle).
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</description>
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</method>
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<method name="Basis">
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@ -7690,7 +7690,7 @@
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<return type="Vector3">
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</return>
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<description>
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Assuming that the matrix is a proper rotation matrix (orthonormal matrix with determinant +1), return Euler angles (in the XYZ convention: first Z, then Y, and X last). Returned vector contains the rotation angles in the format (third,second,first).
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Assuming that the matrix is a proper rotation matrix (orthonormal matrix with determinant +1), return Euler angles (in the YXZ convention: first Z, then X, and Y last). Returned vector contains the rotation angles in the format (X-angle, Y-angle, Z-angle).
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</description>
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</method>
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<method name="get_orthogonal_index">
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