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How Can You Render A Quad From A VBO using PyOpenGL and Pygame?
I am trying to get an image to render on my screen using PyOoenGL and pygame, while not using any VBO's I managed to get it to display using this draw function:
def draw(texture: Texture):
texture.Bind()
glBegin(GL_QUADS)
glTexCoord2f(0, 0)
glVertex2f(-1, -1)
glTexCoord2f(1, 0)
glVertex2f(1, -1)
glTexCoord2f(1, 1)
glVertex2f(1, 1)
glTexCoord2f(0, 1)
glVertex2f(-1, 1)
glEnd()
However, when I tried to change it out to render using a VBO I could not see well... anything:
def GenVBO():
# gen VBO for a quad # glBufferSubData(GL_ARRAY_BUFFER, offset, len(dataArray)*4, dataArray)
VBO = glGenBuffers(1)
glBindBuffer(GL_ARRAY_BUFFER, VBO)
glBufferData(GL_ARRAY_BUFFER, 64, None, GL_STATIC_DRAW)
glBufferSubData(GL_ARRAY_BUFFER, 0, 32, (GLfloat * 12)(-1, -1, 0, 0, 0, 0, 1, -1, 0, 1, 0, 0))
glBindBuffer(GL_ARRAY_BUFFER, 0)
return VBO
def draw(texture: Texture, VBO):
texture.Bind()
glBindBuffer(GL_ARRAY_BUFFER, VBO)
glEnableClientState(GL_VERTEX_ARRAY)
glEnableClientState(GL_TEXTURE_COORD_ARRAY)
glVertexPointer(2, GL_FLOAT, 32, None)
glTexCoordPointer(2, GL_FLOAT, 32, ctypes.c_void_p(8))
glDrawArrays(GL_QUADS, 0, 4)
I do not get any errors, just a blank screen, I have also tried to move around by changing my perspective with a movement script, but still no output.
And just in case it's relevant, here is the main script:
def main():
pygame.init()
display = (800, 600)
pygame.display.set_mode(display, DOUBLEBUF|OPENGL)
glEnable(GL_TEXTURE_2D)
glEnable(GL_BLEND)
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)
gluPerspective(45, (display[0]/display[1]), 0.1, 50.0)
glTranslatef(0.0, 0.0, -5)
texture = LoadImage("test.png")
VBO = GenVBO()
while True:
down = pygame.key.get_pressed()
for event in pygame.event.get():
if event.type == pygame.QUIT:
pygame.quit()
quit()
# (the movement script is here)
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT)
draw(texture, VBO)
pygame.display.flip()
pygame.time.wait(10)
You have 2 possibiliets:
(x0, y0, u0, v0, x1, y1, u1, v1, ...)
In this case stride is 16 bytes, because each attribute tuple has 4*4 bytes (x, y, u, v). The offset of the vertices is 0 and the offset of the texture coordinates is 8 bytes:
bufferData = (GLfloat * 16)(-1, -1, 0, 0, 1, -1, 1, 0, 1, 1, 1, 1, -1, 1, 0, 1)
glBufferData(GL_ARRAY_BUFFER, bufferData, GL_STATIC_DRAW)
glVertexPointer(2, GL_FLOAT, 16, None)
glTexCoordPointer(2, GL_FLOAT, 16, ctypes.c_void_p(8))
(x0, y0, x1, y1, ..., u0, v0, u1, v1, ...)
In this case stride vor the vertices is 8 bytes and the stride for the texture coordinates is 8 bytes. The offset of the vertices is 0 and the offset of the texture coordinates is 32 bytes (8*4):
vertexData = (GLfloat * 8)(-1, -1, 1, -1, 1, 1, -1, 1)
textureData = (GLfloat * 8)( 0, 0, 1, 0, 1, 1, 0, 1)
glBufferData(GL_ARRAY_BUFFER, 64, None, GL_STATIC_DRAW)
glBufferSubData(GL_ARRAY_BUFFER, 0, 32, vertexData)
glBufferSubData(GL_ARRAY_BUFFER, 32, 32, textureData)
glVertexPointer(2, GL_FLOAT, 8, None)
glTexCoordPointer(2, GL_FLOAT, 8, ctypes.c_void_p(32))
cant seem to draw a triangle
import pygame
from pygame.locals import *
import numpy as np
from OpenGL.GL import *
pygame.init()
display = (600,600)
clock = pygame.time.Clock()
pygame.display.set_mode(display, DOUBLEBUF|OPENGL)
positions = [
-0.5, -0.5,
0, 0.5,
0.5, -0.5
]
positions = np.array(positions, dtype=np.float32)
buffer = glGenBuffers(1)
glBindBuffer(GL_ARRAY_BUFFER, buffer)
glBufferData(GL_ARRAY_BUFFER, positions.size, positions, GL_STATIC_DRAW)
glEnableVertexAttribArray(0)
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 8, 0)
run = True
while run:
for event in pygame.event.get():
if event.type == pygame.QUIT:
run = False
pygame.quit()
if not run:
break
glDrawArrays(GL_TRIANGLES, 0, 3)
pygame.display.flip()
is this a python problem or am i writing it wrong ?
The 2nd argument of glBufferData is the buffer size in bytes:
glBufferData(GL_ARRAY_BUFFER, positions.size, positions, GL_STATIC_DRAW)
glBufferData(GL_ARRAY_BUFFER, positions.size*4, positions, GL_STATIC_DRAW)
The parameter size can be omitted:
glBufferData(GL_ARRAY_BUFFER, positions, GL_STATIC_DRAW)
If a named buffer object is bound, then the 6th parameter of glVertexAttribPointer is treated as a byte offset into the buffer object's data store. But the type of the parameter is a pointer anyway (c_void_p).
So if the offset is 0, then the 6th parameter can either be None or c_void_p(0) else the offset has to be caste to c_void_p(0):
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 8, 0)
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 8, None)
Complete example:
import pygame
from pygame.locals import *
import numpy as np
from OpenGL.GL import *
pygame.init()
display = (600,600)
clock = pygame.time.Clock()
pygame.display.set_mode(display, DOUBLEBUF|OPENGL)
positions = [
-0.5, -0.5,
0, 0.5,
0.5, -0.5
]
positions = np.array(positions, dtype=np.float32)
buffer = glGenBuffers(1)
glBindBuffer(GL_ARRAY_BUFFER, buffer)
glBufferData(GL_ARRAY_BUFFER, positions, GL_STATIC_DRAW)
glEnableVertexAttribArray(0)
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 8, None)
run = True
while run:
for event in pygame.event.get():
if event.type == pygame.QUIT:
run = False
glClear(GL_COLOR_BUFFER_BIT)
glDrawArrays(GL_TRIANGLES, 0, 3)
pygame.display.flip()
pygame.quit()
It is hard to know what example will work without knowing what GL version your hardware supports (print (glGetString(GL_VERSION))), but here is a compatibility demo that should work, but you should consider modifying it to at least OpenGL3.3/GLSL 330:
import pygame
from pygame.locals import *
import numpy as np
from OpenGL.GL import *
pygame.init()
display = (600,600)
clock = pygame.time.Clock()
pygame.display.set_mode(display, DOUBLEBUF|OPENGL)
positions = [
-0.5, -0.5,
0, 0.5,
0.5, -0.5
]
vertex_shader_source = """#version 120
attribute vec2 aPos;
varying vec2 pos;
void main()
{
gl_Position = vec4(aPos.x, aPos.y, 0, 1);
pos = aPos;
}"""
fragment_shader_source = """#version 120
varying vec2 pos;
void main()
{
gl_FragColor = vec4(pos.x, pos.y,0,1);
}"""
vertex_shader = glCreateShader(GL_VERTEX_SHADER)
glShaderSource(vertex_shader, vertex_shader_source)
glCompileShader(vertex_shader)
if glGetShaderiv(vertex_shader, GL_COMPILE_STATUS) != GL_TRUE:
raise RuntimeError(glGetShaderInfoLog(vertex_shader))
fragment_shader = glCreateShader(GL_FRAGMENT_SHADER)
glShaderSource(fragment_shader, fragment_shader_source)
glCompileShader(fragment_shader)
if glGetShaderiv(fragment_shader, GL_COMPILE_STATUS) != GL_TRUE:
raise RuntimeError(glGetShaderInfoLog(fragment_shader))
shader_program = glCreateProgram()
glAttachShader(shader_program, vertex_shader)
glAttachShader(shader_program, fragment_shader)
glLinkProgram(shader_program)
positions = np.array(positions, dtype=np.float32)
VAO = glGenVertexArrays(1)
VBO = glGenBuffers(1)
glBindVertexArray(VAO)
glBindBuffer(GL_ARRAY_BUFFER, VBO)
# using positions.size * np.dtype(np.float32).itemsize
# to get the size (in bytes) of the vertex data
glBufferData(GL_ARRAY_BUFFER, positions.size * np.dtype(np.float32).itemsize, \
positions, GL_STATIC_DRAW)
glEnableVertexAttribArray(0)
aPos = glGetAttribLocation(shader_program, 'aPos')
glEnableVertexAttribArray(aPos)
# ctypes.c_void_p(0) to specify the offset (0 wont work)
glVertexAttribPointer(aPos, 2, GL_FLOAT, GL_FALSE, 0, ctypes.c_void_p(0))
if glGetProgramiv(shader_program, GL_LINK_STATUS) != GL_TRUE:
raise RuntimeError(glGetProgramInfoLog(shader_program))
glClearColor(0,0,1,1);
run = True
while run:
for event in pygame.event.get():
if event.type == pygame.QUIT:
run = False
pygame.quit()
if not run:
break
glClear(GL_COLOR_BUFFER_BIT)
glUseProgram(shader_program)
glBindVertexArray(VAO)
glDrawArrays(GL_TRIANGLES, 0, 3)
pygame.display.flip()
Result:
I have spent almost 2-3 hours trying to figure out why I am not getting a rectangle renderered. I am using pygame for making a window, and opengl for rendering onto the window.
what should be happening is a red background with a blue rectangle, but what I am seeing is just the empty red background.
this is the code I used below.
am I uploading things to the shader wrong? or did I miss something.
import pygame
from pygame.locals import *
from OpenGL.GL import *
from OpenGL.GLU import *
import numpy as np
print("import sucessfull")
vertex = """
#version 460 core
layout (location=0) in vec3 position;
out vec4 fColor;
void main(){
fColor = vec4(0,1,0,1);
gl_Position = vec4(position, 1.0);
}
"""
fragment = """
#version 460 core
in vec4 fColor;
out vec4 color;
void main(){
color = fColor;
//gl_FragColor = fColor;
}
"""
def main():
clock = pygame.time.Clock()
pygame.init()
display = (800, 600)
pygame.display.set_mode(display, DOUBLEBUF | OPENGL)
gluPerspective(45, (display[0]/display[1]), 0.1, 1000)
glClearColor(1, 0,0,1)
glTranslatef(0,0,-5)
#############################3
vertexID = glCreateShader(GL_VERTEX_SHADER)
glShaderSource(vertexID, vertex)
fragmentID = glCreateShader(GL_FRAGMENT_SHADER)
glShaderSource(fragmentID, fragment)
glCompileShader(vertexID)
glCompileShader(fragmentID)
program = glCreateProgram()
glAttachShader(program, vertexID)
glAttachShader(program, fragmentID)
glLinkProgram(program)
positions = [
0.5, -0.5, 0.0,
-0.5, 0.5, 0.0,
0.5, 0.5, 0.0,
-0.5, -0.5, 0.0
]
indexes = [
2,1,0,
0,1,3
]
vao = glGenVertexArrays(1)
glBindVertexArray(vao)
vbo = glGenBuffers(1)
glBindBuffer(GL_ARRAY_BUFFER, vbo)
glBufferData(GL_ARRAY_BUFFER, np.array(positions, dtype=np.float32), GL_STATIC_DRAW)
ebo = glGenBuffers(1)
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo)
glBufferData(GL_ELEMENT_ARRAY_BUFFER, np.array(indexes, dtype=np.float32), GL_STATIC_DRAW)
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 12, 0)
glEnableVertexAttribArray(0)
################################
while True:
for event in pygame.event.get():
if event.type == pygame.QUIT:
pygame.quit()
quit()
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
#render here
glUseProgram(program)
glBindVertexArray(vao)
glEnableVertexAttribArray(0)
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0)
glDisableVertexAttribArray(0)
glBindVertexArray(0)
glUseProgram(0)
#***********
pygame.display.flip()
clock.tick(40)
main()
The type of the indices must be integral and correspond to the type specified in the draw call (GL_UNSIGNED_INT). You have to create a NumPy array with the type uint32 instead of float32:
glBufferData(GL_ELEMENT_ARRAY_BUFFER, np.array(indexes, dtype=np.float32), GL_STATIC_DRAW)
glBufferData(GL_ELEMENT_ARRAY_BUFFER, np.array(indexes, dtype=np.uint32), GL_STATIC_DRAW)
If a named buffer object is bound, then the 6th parameter of glVertexAttribPointer is treated as a byte offset into the buffer object's data store. But the type of the parameter is a pointer anyway (c_void_p).
So if the offset is 0, then the 6th parameter can either be None or c_void_p(0) else the offset has to be caste to c_void_p(0):
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 12, 0)
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 12, None)
There is a similar problem with glDrawElements. The last argument is treated as a byte offset:
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0)
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, None)
gluPerspective and glTranslatef set the deprecated fixed function pipeline matrices. This instructions do not make any sense when you use "modern" shader program. Remove this instructions. With modern OpenGL you have to use Uniform variables.
I am trying to draw some traingles and render some texts in screen. But I've observed that memory(RAM) is gradually increasing just only for 6 draw calls. I've 8 GB RAM. When I run the program memory usage goes from 4.2 to 6 within 1 minute. Here is the full code.
from OpenGL.GL import *
from OpenGL.GLU import *
from OpenGL.GL import shaders
from shader import *
import glfw
import freetype
import glm
import numpy as np
from PIL import Image
import math
class CharacterSlot:
def __init__(self, texture, glyph):
self.texture = texture
self.textureSize = (glyph.bitmap.width, glyph.bitmap.rows)
if isinstance(glyph, freetype.GlyphSlot):
self.bearing = (glyph.bitmap_left, glyph.bitmap_top)
self.advance = glyph.advance.x
elif isinstance(glyph, freetype.BitmapGlyph):
self.bearing = (glyph.left, glyph.top)
self.advance = None
else:
raise RuntimeError('unknown glyph type')
def _get_rendering_buffer(xpos, ypos, w, h, zfix=0.0):
return np.asarray([
xpos, ypos + h, 0, 0,
xpos, ypos, 0, 1,
xpos + w, ypos, 1, 1,
xpos, ypos + h, 0, 0,
xpos + w, ypos, 1, 1,
xpos + w, ypos + h, 1, 0
], np.float32)
def init_chars(shaderProgram,window_height,window_width,font_size=24,fontfile = "Vera.ttf"):
glUseProgram(shaderProgram)
#get projection
shader_projection = glGetUniformLocation(shaderProgram, "projection")
W = window_width
H = window_height
projection = glm.ortho(-W/2, W/2, -H/2, H/2)
glUniformMatrix4fv(shader_projection, 1, GL_FALSE, glm.value_ptr(projection))
#disable byte-alignment restriction
glPixelStorei(GL_UNPACK_ALIGNMENT, 1)
face = freetype.Face(fontfile)
face.set_char_size(font_size*64 )
#load first 128 characters of ASCII set
Characters = dict()
for i in range(0,128):
face.load_char(chr(i))
glyph = face.glyph
#generate texture
texture = glGenTextures(1)
glBindTexture(GL_TEXTURE_2D, texture)
glTexImage2D(GL_TEXTURE_2D, 0, GL_RED, glyph.bitmap.width, glyph.bitmap.rows, 0,
GL_RED, GL_UNSIGNED_BYTE, glyph.bitmap.buffer)
#texture options
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR)
#now store character for later use
Characters[chr(i)] = CharacterSlot(texture,glyph)
glBindTexture(GL_TEXTURE_2D, 0)
glUseProgram(0)
return Characters
def render_text(window,shaderProgram,text,x,y,scale,Characters,color=(170,250,255)):
r,g,b = color
glUseProgram(shaderProgram)
#configure VAO/VBO for texture quads
VAO = glGenVertexArrays(1)
glBindVertexArray(VAO)
VBO = glGenBuffers(1)
glBindBuffer(GL_ARRAY_BUFFER, VBO)
glBufferData(GL_ARRAY_BUFFER, 6 * 4 * 4, None, GL_STATIC_DRAW)
glEnableVertexAttribArray(0)
glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, None)
glBindBuffer(GL_ARRAY_BUFFER, 0)
glBindVertexArray(0)
glUniform3f(glGetUniformLocation(shaderProgram, "textColor"),r/255,g/255,b/255)
glActiveTexture(GL_TEXTURE0)
glBindVertexArray(VAO)
for c in text:
ch = Characters[c]
w, h = ch.textureSize
w = w*scale
h = h*scale
vertices = _get_rendering_buffer(x,y,w,h)
#render glyph texture over quad
glBindTexture(GL_TEXTURE_2D, ch.texture)
#update content of VBO memory
glBindBuffer(GL_ARRAY_BUFFER, VBO)
glBufferSubData(GL_ARRAY_BUFFER, 0, vertices.nbytes, vertices)
glBindBuffer(GL_ARRAY_BUFFER, 0)
#render quad
glDrawArrays(GL_TRIANGLES, 0, 6)
#now advance cursors for next glyph (note that advance is number of 1/64 pixels)
x += (ch.advance>>6)*scale
glBindTexture(GL_TEXTURE_2D, 0);
glUseProgram(0)
#UNBIND and DELETE VAO/VBO
glBindVertexArray(0)
glBindBuffer(GL_ARRAY_BUFFER, 0)
glDeleteBuffers(1, id(VBO))
glDeleteBuffers(1, id(VAO))
def triangle(shaderProgram,window,x=0,y=0):
vertices = [-0.5, -0.5, 0.0,
0.5, -0.5, 0.0,
0.0, 0.5, 0.0]
vertices = np.array(vertices, dtype=np.float32)
VBO = glGenBuffers(1)
glBindBuffer(GL_ARRAY_BUFFER, VBO)
glBufferData(GL_ARRAY_BUFFER, vertices.nbytes, vertices, GL_STATIC_DRAW)
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, None)
glEnableVertexAttribArray(0)
#use shader program
glUseProgram(shaderProgram)
#accessing ourColor variable from shaderProgram
vertexColorLoc = glGetUniformLocation(shaderProgram, "ourColor")
glUniform4f(vertexColorLoc, 255, 28/255.0, 20/255.0, 0.7);
#transform matrix
transform = glm.mat4(1)
transform = glm.translate(transform,glm.vec3(x,y,0))
MVP = glGetUniformLocation(shaderProgram, "MVP")
glUniformMatrix4fv(MVP, 1, GL_FALSE, glm.value_ptr(transform))
#drawing trangle
glLineWidth(3)
glDrawArrays(GL_TRIANGLES, 0, 3)
glUseProgram(0)
#UNBIND and DELETE VAO/VBO
glBindVertexArray(0)
glBindBuffer(GL_ARRAY_BUFFER, 0)
glDeleteBuffers(1, id(VBO))
def main():
glfw.init()
window = glfw.create_window(640, 640,"EXAMPLE PROGRAM",None,None)
glfw.make_context_current(window)
#initliaze shader programs
shaderProgram = get_shaderProgram()
text_shaderProgram = get_text_shaderProgram()
#load characters and VAO/VBO for text rendering
Characters = init_chars(text_shaderProgram,640,640)
#window loop
while not glfw.window_should_close(window):
glfw.poll_events()
#screen
glClearColor(0, 0, 0, 1)
glClear(GL_COLOR_BUFFER_BIT)
glEnable(GL_BLEND)
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)
#draw functions
render_text(window,text_shaderProgram,"TRIANGLE",-50,-200,1,Characters)
render_text(window,text_shaderProgram,"A",0,180,1,Characters)
render_text(window,text_shaderProgram,"B",-160,-180,1,Characters)
render_text(window,text_shaderProgram,"C",150,-180,1,Characters)
triangle(shaderProgram,window)
triangle(shaderProgram,window,x=0.5,y=0.5)
#swap buffers
glfw.swap_buffers(window)
glfw.swap_interval(1)
glfw.terminate()
if __name__ == '__main__':
main()
The shader program is here. But I think the problems is in buffer object. I've tried to unbind VAO/VBO and delete buffers by following code. But I see no change.
#UNBIND and DELETE VAO/VBO
glBindVertexArray(0)
glBindBuffer(GL_ARRAY_BUFFER, 0)
glDeleteBuffers(1, id(VBO))
glDeleteBuffers(1, id(VAO))
Here is the related problem where accepted answer suggested that glGenBuffers causes memory leak. The alternate function glCreateBuffers is not available in pyopengl. How can I solve this issue?
I can't see any good reason for recreating the Vertex Array Object and Array Buffer Object every time when render_text respectively triangle is called. The vertex specification and the number of vertices doesn't change, so it would be sufficient to update the content of the buffer.
Create the Vertex Array Object and the Array Buffer Object once at initialization:
def init_buffers():
global text_VAO, text_VBO, triangle_VAO, triangle_VBO
text_VAO = glGenVertexArrays(1)
glBindVertexArray(text_VAO)
text_VBO = glGenBuffers(1)
glBindBuffer(GL_ARRAY_BUFFER, text_VBO)
glBufferData(GL_ARRAY_BUFFER, 6 * 4 * 4, None, GL_STATIC_DRAW)
glEnableVertexAttribArray(0)
glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, None)
vertices = [-0.5, -0.5, 0.0,
0.5, -0.5, 0.0,
0.0, 0.5, 0.0]
vertices = np.array(vertices, dtype=np.float32)
triangle_VAO = glGenVertexArrays(1)
glBindVertexArray(triangle_VAO)
triangle_VBO = glGenBuffers(1)
glBindBuffer(GL_ARRAY_BUFFER, triangle_VBO)
glBufferData(GL_ARRAY_BUFFER, vertices.nbytes, vertices, GL_STATIC_DRAW)
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, None)
glEnableVertexAttribArray(0)
Use then in the functions render_text and triangle:
def render_text(window,shaderProgram,text,x,y,scale,Characters,color=(170,250,255)):
# [...]
glBindVertexArray(text_VAO)
for c in text:
# [...]
glBindBuffer(GL_ARRAY_BUFFER, text_VBO)
glBufferSubData(GL_ARRAY_BUFFER, 0, vertices.nbytes, vertices)
# glDeleteBuffers(1, id(VBO)) <--- DELETE
# glDeleteBuffers(1, id(VAO)) <--- DELETE
def triangle(shaderProgram,window,x=0,y=0):
glBindVertexArray(triangle_VAO)
# [...]
# glDeleteBuffers(1, id(VBO)) <--- DELETE
Invoke init_buffers before the application loop:
def main():
# [...]
init_buffers()
while not glfw.window_should_close(window):
# [...]
I would like to make a mesh with Pyglet that is changing every frame. Therefore I need to update the vertices very often and I thought that a VBO would be the fastest way to go here (correct me if I am wrong). Below an example for Points. Is this the correct way of doing it? I read that the number of glBindBuffer calls should be minimised, but here it is called every frame. also GL_DYNAMIC_DRAW is enabled, but if I change it to GL_STATIC_DRAW it is still working. It makes me wondering if this is a correct setup for fast computation
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()
You don't need to call glBufferData every single time in update - create and fill the VBO once (see setup_initial_points) and only update it with glBufferSubData. In case you are only working with a single VBO, you can also comment out the glBindBuffer call in update() (see code below).
GL_DYNAMIC_DRAW vs GL_STATIC_DRAW won't make a big difference in this example since you are pushing very few data onto 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's 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()