Rust 从光标位置旋转精灵

发布于05月30日

我不明白BEVY的旋转是怎么运作的.我只想旋转一个精灵来跟随我的光标位置.

有没有人能给我一段让它工作的代码？

我试过了，但没用: Bevy rotation in 2d个

use bevy::math::{Quat, Vec2};

let pos = transform.translation.truncate(); // player position
let target = event.position;                // cursor position

let angle = (target - pos).angle_between(pos); // NaN
transform.rotation = Quat::from_rotation_z(angle);

在上面做一个Angular =NaN，所以它不工作.

let pos = transform.translation.truncate(); // player position
let target = cursor_position; // cursor position
            
let direction = target - pos;
let angle = direction.y.atan2(direction.x); // Calculate angle between direction and x-axis
transform.rotation = Quat::from_rotation_z(angle);

结果如下:

这是回购，如果你想试试的话:https://github.com/theocerutti/SpaceGameRust

谢谢!

推荐答案

所需要的是将球员的前部朝向光标旋转.为了做到这一点，还需要描述球员前面的方向的矢量.

angle = (target - pos).angle_between(pos)没有帮助，因为pos没有描述玩家的方位.pos只是玩家的位置.

找到矢量target-pos相对于x轴的Angular 是有用的，但还不够.

从这个Angular ，球员的方向相对于x轴的Angular 应该减go .这将提供所需的旋转Angular .球员应该根据产生的Angular ，围绕通过球员的z轴旋转.

一种解决方案是有一个单独的变量来跟踪对象的方向.该变量必须在每次对象旋转时更新.

use bevy::math::{Quat, Vec2};
use std::f32::consts::PI;

// Initialize player orientation at the very beginning.
// It is the angle with respect to X-axis.
// IMPORTANT NOTE: Check what value it is (0 degrees or 90 degrees etc)
// and set it here.
let player_orient = PI/2.0;

...

let pos = transform.translation.truncate(); // player position
let target = Vec2::new(cursor_position.x - window.width() / 2., cursor_position.y - window.height() / 2.);                // cursor position
let direction = target - pos; 

// obtain angle to target with respect to x-axis. 
let mut angle_to_target = direction.y.atan2(direction.x);
// represent angle_to_target in [0, 2*PI)
if angle_to_target < 0. {
  angle_to_target += 2.0*PI;
}

let angle_to_rotate = angle_to_target - player_orient;
transform.rotation = Quat::from_rotation_z(angle_to_rotate);

// Update the player's orientation.
// Always, represent it in the range [0, 2*PI).
player_orient = (player_orient + angle_to_rotate) % (2.0*PI);