How to update data using VBO and Pyglet
I would like to create a grid with Pyglet that changes every frame. So I need to update the vertices very often and I thought VBO would be the fastest way to go here (correct me if I'm wrong). Below is an example for glasses. Is it correct? I read that the number of glBindBuffer calls should be kept to a minimum, but here it is called each frame. also included GL_DYNAMIC_DRAW, but if I change it to GL_STATIC_DRAW it still works. This makes me wonder if this is the correct setup for a quick calculation
import pyglet
import numpy as np
from pyglet.gl import *
from ctypes import pointer, sizeof
vbo_id = GLuint()
glGenBuffers(1, pointer(vbo_id))
window = pyglet.window.Window(width=800, height=800)
glClearColor(0.2, 0.4, 0.5, 1.0)
glEnableClientState(GL_VERTEX_ARRAY)
c = 0
def update(dt):
global c
c+=1
data = (GLfloat*4)(*[500+c, 100+c,300+c,200+c])
glBindBuffer(GL_ARRAY_BUFFER, vbo_id)
glBufferData(GL_ARRAY_BUFFER, sizeof(data), 0, GL_DYNAMIC_DRAW)
glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(data), data)
pyglet.clock.schedule(update)
glPointSize(10)
@window.event
def on_draw():
glClear(GL_COLOR_BUFFER_BIT)
glColor3f(0, 0, 0)
glVertexPointer(2, GL_FLOAT, 0, 0)
glDrawArrays(GL_POINTS, 0, 2)
pyglet.app.run()
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You don't need to call glBufferData
every time on update - create and populate the VBO once (see setup_initial_points
) and update it with just glBufferSubData
. If you are working with only one VBO, you can also comment out the call glBindBuffer
in update()
(see code below).
GL_DYNAMIC_DRAW
vs GL_STATIC_DRAW
won't make much of a difference in this example as you are pushing very little data to the GPU.
import pyglet
from pyglet.gl import *
from ctypes import pointer, sizeof
window = pyglet.window.Window(width=800, height=800)
''' update function '''
c = 0
def update(dt):
global c
c+=1
data = calc_point(c)
# if there only on VBO, you can comment out the 'glBindBuffer' call
glBindBuffer(GL_ARRAY_BUFFER, vbo_id)
glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(data), data)
pyglet.clock.schedule(update)
''' draw function '''
@window.event
def on_draw():
glClear(GL_COLOR_BUFFER_BIT)
glColor3f(0, 0, 0)
glVertexPointer(2, GL_FLOAT, 0, 0)
glDrawArrays(GL_POINTS, 0, 2)
''' calculate coordinates given counter 'c' '''
def calc_point(c):
data = (GLfloat*4)(*[500+c, 100+c, 300+c, 200+c])
return data
''' setup points '''
def setup_initial_points(c):
vbo_id = GLuint()
glGenBuffers(1, pointer(vbo_id))
data = calc_point(c)
glBindBuffer(GL_ARRAY_BUFFER, vbo_id)
glBufferData(GL_ARRAY_BUFFER, sizeof(data), 0, GL_DYNAMIC_DRAW)
return vbo_id
############################################
vbo_id = setup_initial_points(c)
glClearColor(0.2, 0.4, 0.5, 1.0)
glEnableClientState(GL_VERTEX_ARRAY)
glPointSize(10)
pyglet.app.run()
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