[英]How can I write this C# Z-axis vector rotation in JavaScript?
I have written a very simple XNA game in C# that uses the following method to rotationally alter projectiles as they fly towards a target. 我已经用C#编写了一个非常简单的XNA游戏,该游戏使用以下方法在弹丸飞向目标时旋转改变弹丸。 The objective of this is to make the projectiles somewhat 'homing': 这样做的目的是使弹丸有些“归巢”:
float rotation;
Vector2 velocity;
int speed;
public void SetRotation(float value) // Make the projectiles homing
{
rotation = value;
velocity = Vector2.Transform(new Vector2(0, -speed),
Matrix.CreateRotationZ(rotation));
}
I am trying (for my own learning purposes - I am very new to JavaScript) to port my game to JavaScript and allow it to be played inside a canvas. 我正在尝试(出于我自己的学习目的-我对JavaScript非常陌生)将我的游戏移植到JavaScript并允许它在画布中播放。 Could anyone suggest how I could re-write the above method as a JS function? 谁能建议我如何将上述方法重写为JS函数?
As someone who is a complete beginner to JavaScript would this most easily be done using an existing framework of some kind? 作为JavaScript的完整入门者,使用现有的某种框架最容易做到这一点吗?
The method of rotating a vector involves some basic matrix math. 旋转向量的方法涉及一些基本矩阵数学。 (Please forgive the ASCII art. No LaTeX makes this more difficult) (请原谅ASCII文字。没有LaTeX会使这更加困难)
First represent the vector in homogenous-coordinate form: 首先以均匀坐标形式表示向量:
[ x ]
v = | y |
| z |
[ 1 ]
The rotation matrix is provided by: 旋转矩阵由以下方式提供:
[ cos(r) -sin(r) 0 0 ]
M = | sin(r) cos(r) 0 0 |
| 0 0 1 0 |
[ 0 0 1 1 ]
Where r
is the amount of rotation about Z
其中r
是绕Z
的旋转量
To apply the transformation, multiply the matrix M
by the vector v
: 要应用转换,请将矩阵M
乘以向量v
:
[ cos(r) -sin(r) 0 0 ] [ x ]
v' = Mv = | sin(r) cos(r) 0 0 | * | y |
| 0 0 1 0 | | z |
[ 0 0 0 1 ] [ 1 ]
Simplifying the multiplication gives the formula 简化乘法给出公式
v' = { x' = x * cos(r) - y * sin(r)
{ y' = x * sin(r) + y * cos(r)
{ z' = z
(Note: in Javascript, the sin()
and cos()
functions take arguments in radians.) (注意:在Javascript中, sin()
和cos()
函数采用弧度表示参数。)
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