概述

平面图形，除了常规的线性变换：平移、缩放、旋转、斜切之外。还可以模仿在三维空间旋转、透视等等。

矩形绕纵对称轴旋转实点的轨迹

• 绕对称旋转是个特殊情况，轨迹是圆也是为了便于理解。更实际的情况应该是椭圆。
• 非对称轴旋转的情况轨迹更可能是同心椭圆。
• 矩形更是个特殊情况，在一个矩形包围盒中的多边旋转，更是多个同心或非同心椭圆。

测试代码

@tool
extends Node2D

var rect = Rect2(-50,-50,100,100)  # 透视图形
var points = ShapeTests.get_rect_points(rect)
var uvs = Points2D.Vec2Arr("1,0 0,0 0,1 1,1")

@export_range(-360.0,360.0,1.0) var theta = 0:
	set(val):
		theta = val
		queue_redraw()

@export var texture:Texture2D:
	set(val):
		texture = val
		queue_redraw()


func _draw() -> void:
	var top_c = rect.position + Vector2(rect.size.x/2.0,0) # 顶部中点
	var bot_c = rect.end - Vector2(rect.size.x/2.0,0)      # 底部中点
	var half_w = rect.size/2.0
	
	#draw_colored_polygon(points,Color.AQUAMARINE)
	
	
	
	var new_points = points.duplicate()
	new_points[0] = top_c + Vector2.LEFT.rotated(deg_to_rad(theta)) * half_w
	new_points[1] = top_c + Vector2.RIGHT.rotated(deg_to_rad(theta)) * half_w
	new_points[2] = bot_c + Vector2.RIGHT.rotated(deg_to_rad(-theta)) * half_w
	new_points[3] = bot_c + Vector2.LEFT.rotated(deg_to_rad(-theta)) * half_w
	
	
	draw_colored_polygon(new_points,Color.AQUAMARINE,uvs,texture)
	draw_circle(top_c,3,Color.ORANGE_RED)
	draw_circle(bot_c,3,Color.ORANGE_RED)

实现效果：

但是贴图会发生错误：

总结函数

# 将矩形沿Y轴旋转
func rotate_y(rect:Rect2,theta:float) -> PackedVector2Array:
	var ang = deg_to_rad(theta)
	var top_c = rect.position + Vector2(rect.size.x/2.0,0) # 顶部中点
	var bot_c = rect.end - Vector2(rect.size.x/2.0,0)      # 底部中点
	var half_w = rect.size/2.0
	
	var points = ShapeTests.get_rect_points(rect)
	points[0] = top_c + Vector2.LEFT.rotated(ang) * half_w
	points[1] = top_c + Vector2.RIGHT.rotated(ang) * half_w
	points[2] = bot_c + Vector2.RIGHT.rotated(-ang) * half_w
	points[3] = bot_c + Vector2.LEFT.rotated(-ang) * half_w
	return points

# 将矩形沿X轴旋转
func rotate_x(rect:Rect2,theta:float) -> PackedVector2Array:
	var ang = deg_to_rad(theta)
	var left_c = rect.position + Vector2(0,rect.size.y/2.0) # 顶部中点
	var right_c = rect.end - Vector2(0,rect.size.y/2.0)      # 底部中点
	var half_h = rect.size/2.0
	
	var points = ShapeTests.get_rect_points(rect)
	points[0] = left_c + Vector2.UP.rotated(ang) * half_h
	points[1] = left_c + Vector2.DOWN.rotated(ang) * half_h
	points[2] = right_c + Vector2.DOWN.rotated(-ang) * half_h
	points[3] = right_c + Vector2.UP.rotated(-ang) * half_h
	return points

注意：其实上面的代码中有一个Bug，就是half_w = rect.size/2.0和half_h = rect.size/2.0,但是就是这个Bug莫名其妙的导致了边长不等的矩形旋转的的完美，有时候就是这样，哈哈哈…你根本不知道你的代码为什么顺利运行。

上述两个新函数已经作为静态函数库ShapeTests的静态方法，可以直接调用。