Hi,
Pyglet typically uses double buffering [0]: one picture (buffer) is
being drawn, while another is being displayed in the window. Then, they
are flipped, so what was drawn is now displayed, and drawing is done on
the hidden buffer.
This prevents partially-drawn buffers from being displayed.
So, if you clear every 2 frames, you're only ever clearing one of the
two buffers; the other one continues to accumulate whatever was drawn on it.
You can tell Pyglet to turn double buffering on or off using context
configuration [1]. (I guess the proper solution would be to draw to a
dedicated buffer, and blit that to the screen. But I've never done that
with Pyglet.)
For your effect, you might also consider drawing a semi-transparent
black rectangle over the screen, rather than clearing every few frames.
But be sure to clear the buffer at the beginning. Some systems don't
start you off with a black window.
[0]
https://en.wikipedia.org/wiki/Multiple_buffering#Double_buffering_in_computer_graphics
[1]
http://pyglet.readthedocs.io/en/pyglet-1.2-maintenance/programming_guide/windowing.html
On 12/13/2016 07:33 AM, xinming wrote:
Sorry, I did not describe my problem clearly. It would work without
raising errors, however, if I set in odd it would works fine, the
screenshot here:
if set even number, it seemed
that glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT) did not work, so I
said failed, here is the screenshot if I change 5 to 6.
At 2016-12-13 14:24:01, "..." <offonoffoffon...@gmail.com> wrote:
What do you mean "it failed"? Can you post a traceback or describe
how the result differs from your expectation?
On Dec 12, 2016 10:34 PM, "Simon" <xinmingm...@163.com
<mailto:xinmingm...@163.com>> wrote:
Hi guys, I met a strange problem. I use pyglet building an app
to simulate fireworks. And I want to add special effects of
persistence of vision. I do not know how to do it, I just do it
in my own way. Maybe you can tell me how to do it. My problem is
that I update the background
(glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT)) every 3, 5, 7
frames, it works. If I update the background every 2,4,6,8
frames, it failed. why?
my code is like this
def on_draw(self):
glViewport(0, 0, window.width, window.height)
glMatrixMode(gl.GL_PROJECTION)
glLoadIdentity()
gluPerspective(90,window.width/window.height,0.05,1000)
glMatrixMode(gl.GL_MODELVIEW)
glLoadIdentity()
gluLookAt(0.0,0.0,4.0,
0.0,0.0,0.0,
0.0,1.0,0.0)
if self.frame % 5 == 1: #
if change 5 to even number 4,6,8, it failed
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT)
full code can be found here
<https://github.com/xinmingzhang/fireworks/blob/master/fireworks.py>
And I am new to OpenGL, I also lost in setting these gl
environment, like gl.GL_PROJECTION, gl.GL_MODELVIEW etc.
Sometimes I set the projection, and I see nothing on screen. Is
there any good suggestions?
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