How to implement Unity's Quaternion.Euler ?

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:bust_in_silhouette: Asked By Dentrax

Hello,

I am implementing a simple spawner in 2D mode. My aim is to make them (each node) spawn with a 30-degree angle.

In Unity, I can solve this problem via Euler.

Vector2 v = Vector2.zero - base.transform.position;
v = Quaternion.Euler(0f, 0f, 30f) * v;

In Godot, how can I create a function that is exactly equivalent?

Currently, my implementation is:

var vector = target.position - position
var right = Quat(Vector3(vector.x, vector.y, 0), 30);
var left = Quat(Vector3(vector.x, vector.y, 0), -30);

if index == 1:
	vector.x = right.get_euler().x * vector.x;
	vector.y = right.get_euler().y * vector.y;
elif index == 2:
	vector.x = left.get_euler().x * vector.x;
	vector.y = left.get_euler().y * vector.y;

But it works wrong. The ‘left’ is throwing the back side and the angle of both ‘left’ and ‘right’ is not 30 degrees.

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:bust_in_silhouette: Reply From: hammeron

You can rotate a vector with a Transform2D.
Also note that angles in Godot are in radians.

var m = Transform2D().rotated(deg2rad(30));
# Clockwise rotation
var new_pos = m * vector;

# Counterclockwise 
new_pos = m.xform_inv(vector);

In-depth explanation about Transforms: Matrices and transforms — Godot Engine (3.1) documentation in English

Thank you it’s working fine. :slight_smile:

Dentrax | 2019-04-04 10:35

3
:bust_in_silhouette: Reply From: brainbug 
var q = Quat()
q.set_euler(Vector3(yaw,tilt,roll))
v = q * v

the angles must be in radians!!

Well, how can i change the (x, y) at the same time with the given angle via Euler?

vector = get_rotated_vector(vector, 35)

Like this:

func get_rotated_vector(vector, degrees):
	var sinr = sin(degrees * PI/180);
	var cosr = cos(degrees * PI/180);
	
	vector.x = (cosr * vector.x) - (sinr * vector.y);
	vector.y = (sinr * vector.x) + (cosr * vector.y);
	
	return vector;

P.S: I get this code from StackOverflow, I couldn’t find the source, sorry.

Dentrax | 2019-04-04 10:42