Godot 运动的像素点

一条直线上运动

using Godot;
using System;

public class Line : Node2D
{
    [Export]
    //Pixel/s
    public float v = 100;
    [Export]
    public Vector2 direction = new Vector2(2, 1);
    private Rect2 screenRect;
    private Vector2 Point = new Vector2(1, 1);
    private Color color = new Color("60C5F1");
    /*
	x,y,len
	b = x / y, x = yb, len = vt
	sqrt(y^2(b^2+1)) = len
	y =sqrt(len^2/(b^2+1)) = len/sqrt(b^2+1) = vt/sqrt(b^2+1)
	 */
    private float x1;
    private float y1;

    public Line()
    {
        UpdateDirection();
    }

    public override void _Ready()
    {
        screenRect = GetViewport().GetVisibleRect();
    }

    private void UpdateDirection()
    {
        if (direction.x == 0)
        {
            x1 = 0;
            y1 = v;
            return;
        }
        else if (direction.y == 0)
        {
            y1 = 0;
            x1 = v;
        }

        var b = direction.x / direction.y;
        y1 = (direction.y > 0 ? 1 : -1) * v / Mathf.Sqrt(Mathf.Pow(b, 2) + 1);
        x1 = (direction.x > 0 ? 1 : -1) * b * v / Mathf.Sqrt(Mathf.Pow(b, 2) + 1);
    }

    public override void _Process(float delta)
    {
        var y = y1 * delta;
        var x = x1 * delta;
        Point.x += x;
        Point.y += y;

        Update();
        if (!screenRect.HasPoint(Point))
        {
            direction = -direction;
            UpdateDirection();
        }
    }

    private void _on_Line_draw()
    {
        DrawCircle(Point, 2, color);
    }
}

圆形上运动

using Godot;
using System;

public class Circle : Node2D
{
    private Vector2 start = new Vector2(200, 200);
    private Vector2 current = new Vector2(300, 200);
    [Export]
    //Pixel/s
    public float v = 100;
    //radius Pixel
    private float r = 100;
    //radian = arc length/radius = v*t / radius
    private float v_r_ratio;
    private float rad = 0;
    private Color color = new Color("60C5F1");
    private float maxrad = 2 * Mathf.Pi;

    public Circle()
    {
        v_r_ratio = v / r;
    }

    public override void _Process(float delta)
    {
        if (rad > maxrad)
        {
            rad -= maxrad;
        }

        rad += delta * v_r_ratio;
        var y = r * Mathf.Sin(rad);
        var x = r * Mathf.Cos(rad);

        current.x = start.x + x;
        current.y = start.y + y;

        Update();
    }

    private void _on_Circle_draw()
    {
        DrawCircle(current, 2, color);
    }
}