glDrawArrays returning invalid operation 1282 - pyOpenGL

Question

I cannot figure this out for the life of me. I need a second pair of eyes ... or a better brain. I am trying to get this "Hello Triangle" python example working. I've been translating it from a c tutorial. However, I keep getting this error no matter what I do.

Traceback (most recent call last):
File ".../demo/tester.py", line 107, in <module>
  if __name__ == '__main__': main()
File ".../demo/tester.py", line 87, in main
  glDrawArrays(GL_TRIANGLES, 0, 3)
File ".../venv/lib/python3.6/site packages/OpenGL/platform/baseplatform.py", line 402, in __call__
  return self( *args, **named )
File ".../venv/lib/python3.6/site-packages/OpenGL/error.py", line 232, in glCheckError
  baseOperation = baseOperation,
OpenGL.error.GLError: GLError(
  err = 1282,
  description = b'invalid operation',
  baseOperation = glDrawArrays,
  cArguments = (GL_TRIANGLES, 0, 3)

My code is below. I am running on a Mac so you'll notice some things in there that might not be needed for PC. Everything works fine up until the glDrawArrays. I know that some of the functions between openGL for C vs python using pyOpenGL are a bit different. I've been cross referencing the documentation to make sure I am not trying write like a C programmer in Python.

try:
    from AppKit import NSApp, NSApplication
except:
    pass

import sys
import cyglfw3 as glfw
import numpy as np
from OpenGL.GL import *
from OpenGL.GLUT import *
from OpenGL.arrays import vbo as glvbo



def main():
    glfw.Init()
    glfw.WindowHint(glfw.CONTEXT_VERSION_MAJOR, 3)
    glfw.WindowHint(glfw.CONTEXT_VERSION_MINOR, 3)
    glfw.WindowHint(glfw.OPENGL_PROFILE, glfw.OPENGL_CORE_PROFILE)
    glfw.WindowHint(glfw.OPENGL_FORWARD_COMPAT, GL_TRUE)

    window = glfw.CreateWindow(800, 600, 'LearnOpenGL', None)
    if window is None:
        glfw.Terminate()
        exit()

    glfw.MakeContextCurrent(window)
    glfw.SetFramebufferSizeCallback(window, framebuffer_size_callback())

    # Setting up a vertex buffer
    verts = glvbo.VBO(
    np.array([[0.0, 0.5, 0.0], [0.5, -0.5, 0.0], [-0.5, -0.5, 0.0]], 'f')
)

    vbo = glGenBuffers(1)
    glBindBuffer(GL_ARRAY_BUFFER, vbo)
    glBufferData(GL_ARRAY_BUFFER, verts.size, verts, GL_STATIC_DRAW)

    vao = glGenVertexArrays(1)
    glBindVertexArray(vao)
    glEnableVertexAttribArray(vao)
    glBindBuffer(GL_ARRAY_BUFFER, vbo)
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, None)

    vertex_shader = """
        #version 330 core
        in vec3 vp;
        void main() {
            gl_Position = vec4(vp, 1.0);
        }"""

    fragment_shader = """
        #version 330 core
        out vec4 frag_color;
        void main() {
            frag_color = vec4(0.5, 0.0, 0.5, 1.0);
        }"""

    vs = glCreateShader(GL_VERTEX_SHADER)
    glShaderSource(vs, vertex_shader)
    glCompileShader(vs)

    if glGetShaderiv(vs, GL_COMPILE_STATUS) != GL_TRUE:
        raise Exception("vertex shader did not compile")

    fs = glCreateShader(GL_FRAGMENT_SHADER)
    glShaderSource(fs, fragment_shader)
    glCompileShader(fs)

    if glGetShaderiv(fs, GL_COMPILE_STATUS) != GL_TRUE:
        raise Exception("fragment shader did not compile")

    sp = glCreateProgram()
    glAttachShader(sp, fs)
    glAttachShader(sp, vs)
    glLinkProgram(sp)

    if glGetProgramiv(sp, GL_LINK_STATUS) != GL_TRUE:
        raise Exception("program did not link")

    while not glfw.WindowShouldClose(window):

        processInput(window)

        glClearColor(0.0, 0.0, 0.0, 1.0)
        glClear(GL_COLOR_BUFFER_BIT)

        glUseProgram(sp)
        glBindVertexArray(vao)
        glDrawArrays(GL_TRIANGLES, 0, 3)    # This is where things happen

        glfw.PollEvents()
        glfw.SwapBuffers(window)

    glfw.Terminate()
    exit()

def framebuffer_size_callback():
    glViewport(0, 0, 800, 600)

def processInput(window):
    if glfw.GetKey(window, glfw.KEY_ESCAPE) == glfw.PRESS:
        glfw.SetWindowShouldClose(window, True)

if __name__ == '__main__': main()

All I want to do at the end of the day, is draw a triangle :(

glEnableVertexAttribArray(vao) looks wrong. Instead of vao, you have to enable the attribute location of vp. But this would probably not cause a invalid operation error. — BDL
You should check if your shader compiled and linked fine (glGetShaderiv/glGetProgramvi). — BDL
What do you mean the location of vp? I added exceptions and did not get issues with the shaders and program. — Adam Adam Adam
@BDL - I noticed it requires an index. I passed in a 0 for the index. It runs now without issue but does not show my triangle :) — Adam Adam Adam

Adam Adam Adam Adam Adam Adam · Accepted Answer · 2018-03-15T16:42:58

I determined there were 2 issues.

As BDL mentioned the glEnableVertexAttribArray was not setup appropriately. It needed an index and not a vertex array object.
The glBufferData size was incorrect as the size needed to be provided in bytes. A quick search online revealed that (numpy.size * numpy.itemsize) returns the size of the array.

With these 2 things done... I have a triangle.

glDrawArrays returning invalid operation 1282 - pyOpenGL

1 Answers