pyglet when using draw() instead of eventloop

Question

I'm trying to draw a circle with pyglet. But it is not visible when I use the draw() function instad of the app.run() loop. Any suggestions what I can do? thanks

from math import *
from pyglet.gl import *

window = pyglet.window.Window()

def makeCircle(x_pos, y_pos, radius, numPoints):
    verts = []
    glClear(pyglet.gl.GL_COLOR_BUFFER_BIT)
    glColor3f(1,1,0)
    for i in range(numPoints):
        angle = radians(float(i)/numPoints * 360.0)
        x = radius *cos(angle) + x_pos
        y = radius *sin(angle) + y_pos
        verts += [x,y]
    circle = pyglet.graphics.vertex_list(numPoints, ('v2f', verts))
    circle.draw(GL_LINE_LOOP)
    input()

makeCircle(5,5, 100, 10)

Answer 1

You've to call window.flip() to update the window.

Since you don't have set a projection matrix, the geometry has to be draw in normalized device coordinates, which are in range [-1, 1] for all 3 components (x, y, z). Note, pyglet set a projection matrix by default when the application is started by pyglet.app.run().

Call window.flip() and change the geometry:

from math import *
from pyglet.gl import *

window = pyglet.window.Window()

def makeCircle(x_pos, y_pos, radius, numPoints):
    verts = []
    glClear(pyglet.gl.GL_COLOR_BUFFER_BIT)
    glColor3f(1,1,0)
    for i in range(numPoints):
        angle = radians(float(i)/numPoints * 360.0)
        x = radius *cos(angle) + x_pos
        y = radius *sin(angle) + y_pos
        verts += [x,y]
    circle = pyglet.graphics.vertex_list(numPoints, ('v2f', verts))
    circle.draw(GL_LINE_LOOP)

    window.flip()           # <--------

    input()

makeCircle(0, 0, 0.5, 10)   # <--------

---

Alternatively you can set an orthographic projection on your own, by glOrtho. e.g.:

from math import *
from pyglet.gl import *

window = pyglet.window.Window()

def makeCircle(x_pos, y_pos, radius, numPoints):
    verts = []

    glMatrixMode(GL_PROJECTION)
    glOrtho(0, 640, 0, 480, -1, 1)
    glMatrixMode(GL_MODELVIEW)

    glClear(pyglet.gl.GL_COLOR_BUFFER_BIT)
    glColor3f(1,1,0)
    for i in range(numPoints):
        angle = radians(float(i)/numPoints * 360.0)
        x = radius *cos(angle) + x_pos
        y = radius *sin(angle) + y_pos
        verts += [x,y]
    circle = pyglet.graphics.vertex_list(numPoints, ('v2f', verts))
    circle.draw(GL_LINE_LOOP)

    text = 'This is a test but it is not visible'
    label = pyglet.text.Label(text, font_size=36,
                          x=10, y=10, anchor_x='left', anchor_y='bottom',
                          color=(255, 123, 255, 255))
    label.draw()

    window.flip()
    input()

makeCircle(5,5, 100, 10)