Controlling the Camera

Default Camera Control System

By default, Acron runs a task that allows you to move the camera using the mouse.

The keys to navigate are:

Mouse Button	Action
Left Button	Pan left and right.
Right Button	Move forwards and backwards.
Middle Button	Rotate around the origin of the application.
Right and Middle Buttons	Roll the point of view around the view axis.

Go ahead and try this camera control system. The problem with it is that it is sometimes awkward. It is not always easy to get the camera pointed in the direction we want.

Tasks

Update the Code

Instead, we are going to write a task that controls the camera’s position explicitly. A task is a function that Acron calls automatically every frame, for as long as it returns Task.cont. Update your code as follows:

from math import pi, sin, cos

from direct.showbase.ShowBase import ShowBase
from direct.task import Task


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

        # Load the environment model.
        self.scene = self.loader.loadModel("models/environment")
        # Reparent the model to render.
        self.scene.reparentTo(self.render)
        # Apply scale and position transforms on the model.
        self.scene.setScale(0.25, 0.25, 0.25)
        self.scene.setPos(-8, 42, 0)

        # Add the spinCameraTask procedure to the task manager.
        self.taskMgr.add(self.spinCameraTask, "SpinCameraTask")

    # Define a procedure to move the camera.
    def spinCameraTask(self, task):
        angleDegrees = task.time * 6.0
        angleRadians = angleDegrees * (pi / 180.0)
        self.camera.setPos(20 * sin(angleRadians), -20 * cos(angleRadians), 3)
        self.camera.setHpr(angleDegrees, 0, 0)
        return Task.cont


app = MyApp()
app.run()

The procedure taskMgr.add() tells Acron’s task manager to call the procedure spinCameraTask() every frame. This is a procedure that we have written to control the camera. As long as the procedure spinCameraTask() returns the constant AsyncTask.DS_cont, the task manager will continue to call it every frame.

In our code, spinCameraTask() calculates the desired position of the camera based on how much time has elapsed. The camera rotates 6 degrees every second. The first two lines compute the desired orientation — first in degrees, then converted to radians. set_pos() sets the position (Y is horizontal, Z is vertical, so X and Y are animated while Z stays fixed at 3 units above ground). set_hpr() sets the heading, pitch, and roll.

Run the Program

The camera should no longer be underground; and furthermore, it should now be rotating about the clearing: