Panda3D: 用线段绘制立方体边框的函数

下面是使用Panda3D库在Python中编写的一个函数，该函数根据传入的最小值和最大值，使用线段绘制出立方体的边框：

from panda3d.core import LineSegs
from panda3d.core import NodePath

def draw_cube(min_val, max_val):
    # 创建一个LineSegs对象
    lines = LineSegs()
    
    # 获取立方体的8个顶点
    vertices = [(min_val[0], min_val[1], min_val[2]), 
                (max_val[0], min_val[1], min_val[2]), 
                (min_val[0], max_val[1], min_val[2]), 
                (max_val[0], max_val[1], min_val[2]), 
                (min_val[0], min_val[1], max_val[2]), 
                (max_val[0], min_val[1], max_val[2]), 
                (min_val[0], max_val[1], max_val[2]), 
                (max_val[0], max_val[1], max_val[2])]
    
    # 绘制立方体的12条边
    lines.moveTo(vertices[0])
    lines.drawTo(vertices[1])
    lines.drawTo(vertices[3])
    lines.drawTo(vertices[2])
    lines.drawTo(vertices[0])
    
    lines.moveTo(vertices[4])
    lines.drawTo(vertices[5])
    lines.drawTo(vertices[7])
    lines.drawTo(vertices[6])
    lines.drawTo(vertices[4])
    
    lines.moveTo(vertices[0])
    lines.drawTo(vertices[4])
    
    lines.moveTo(vertices[1])
    lines.drawTo(vertices[5])
    
    lines.moveTo(vertices[2])
    lines.drawTo(vertices[6])
    
    lines.moveTo(vertices[3])
    lines.drawTo(vertices[7])
    
    # 创建一个NodePath对象来容纳线段
    node = NodePath(lines.create())
    
    # 将线段添加到场景图中
    node.reparentTo(render)

要使用此函数，在Panda3D场景的适当位置调用draw_cube函数，并传入所需的最小值和最大值。例如，可以在render函数中调用此函数：

from direct.showbase.ShowBase import ShowBase

class MyApp(ShowBase):
    def __init__(self):
        ShowBase.__init__(self)
        
        # 设置相机位置和方向
        self.camera.setPos(0, -20, 0)
        self.camera.lookAt(0, 0, 0)
        
        # 绘制立方体边框
        min_val = (-5, -5, -5)
        max_val = (5, 5, 5)
        self.draw_cube(min_val, max_val)
        
app = MyApp()
app.run()

运行以上代码将创建一个包含立方体边框的Panda3D窗口。