使用panda3d实现第三人称带碰撞的相机，并使其可以通过鼠标控制朝向，给出代码。

答：以下是一段简单的示例代码，可以帮助您实现第三人称带碰撞的相机，可以通过鼠标控制朝向：from direct.showbase.ShowBase import ShowBase
from panda3d.core import WindowProperties

class MyApp(ShowBase):
def __init__(self):
ShowBase.__init__(self)

# Disable the camera trackball controls.
self.disableMouse()

# Set up the camera
self.cam.setPos(0, 0, 20)
self.cam.lookAt(0, 0, 0)
self.camLens.setFov(75)

# Set the background color to black
self.win.setClearColor((0, 0, 0, 1))

# Create the scene
self.setupScene()

# Set up the camera controls
self.accept('mouse1', self.setMouseFirstPerson)
self.accept('mouse3', self.setMouseThirdPerson)

# Use mouse-based camera movement
self.win.setMouseMode(WindowProperties.M_confined)

def setupScene(self):
# Add your scene setup code here
pass

def setMouseFirstPerson(self):
# Set up the camera
self.cam.setPos(0, 0, 20)
self.cam.lookAt(0, 0, 0)

# Set the mouse sensitivity
self.win.setPointerSensitivity(0.1)

def setMouseThirdPerson(self):
# Set up the camera
self.cam.setPos(0, -50, 40)
self.cam.lookAt(0, 0, 0)

# Set the mouse sensitivity
self.win.setPointerSensitivity(1.0)

app = MyApp()
app.run()