Trying to rotate a quad in 3d using Vispy

I am trying to rotate a textured quad in 3d using Vispy, but I can't seem to work it out. The code isn't producing any particular errors, but it's not rotating at all. I am new to Vispy, maybe I am missing some vital components in my code. Maybe some of you already solved similar problems before. Giving me some insights will be of great help. Here is the code:

import numpy as np

from vispy import gloo, app
app.use_app('pyqt5')
from vispy.gloo import Program
from vispy.util.transforms import perspective, translate, rotate
import imageio


im = imageio.imread('C:\\vhosts\\VIDEO_TWO_CLONE\\fol1\\im.jpg')


vertex = """
    uniform   mat4 u_model;
    attribute vec2 position;
    attribute vec2 texcoord;
    varying vec2 v_texcoord;
    void main()
    {
        gl_Position = u_model * vec4(position, 0.0, 1.0);
        v_texcoord = texcoord;
    } """

fragment = """
    uniform sampler2D texture;
    varying vec2 v_texcoord;
    void main()
    {
        gl_FragColor = texture2D(texture, v_texcoord);
    } """


def checkerboard(grid_num=8, grid_size=32):
    row_even = grid_num // 2 * [0, 1]
    row_odd = grid_num // 2 * [1, 0]
    Z = np.row_stack(grid_num // 2 * (row_even, row_odd)).astype(np.uint8)
    return 255 * Z.repeat(grid_size, axis=0).repeat(grid_size, axis=1)


class Canvas(app.Canvas):
    def __init__(self):
        app.Canvas.__init__(self, size=(512, 512), title='Textured quad',
                            keys='interactive')

        self.model = np.eye(4, dtype=np.float32)
        # Build program & data
        self.program = Program(vertex, fragment, count=4)
        self.program['position'] = [(1, 1), (-1, 1),
                                    (1, -1), (-1, -1)]
        self.program['texcoord'] = [(0, 0), (1, 0), (0, 1), (1, 1)]
        self.program['texture'] = im # checkerboard()
        self.program['u_model'] = self.model



        self.theta = 0
        self.phi = 0


        gloo.set_viewport(0, 0, *self.physical_size)

        self.show()

    def on_draw(self, event):
        gloo.set_clear_color('white')
        gloo.clear(color=True)
        self.program.draw('triangle_strip')


    def on_timer(self, event):
        self.theta += .5
        self.phi += .5
        self.model = np.dot(rotate(self.theta, (0, 1, 0)),
                            rotate(self.phi, (0, 0, 1)))
        self.program['u_model'] = self.model
        self.update()


    def on_resize(self, event):
        gloo.set_viewport(0, 0, *event.physical_size)

if __name__ == '__main__':
    c = Canvas()
    app.run()

Solution

The matrix uniform model, which defines the location and rotation of the model is set up in the method on_timer. Every time on_timer is executed the model matrix changes and rotates the model. But it seems that the timer is never started and on_timer is never executed.

To start the timer you have to call app.Timer during your initializations. Put something similar to the following code in the constructor of the class Canvas:

class Canvas(app.Canvas):
    def __init__(self):
        app.Canvas.__init__(self, size=(512, 512), title='Textured quad', keys='interactive')

        .......

        self._timer = app.Timer('auto', connect=self.on_timer, start=True)