"RuntimeError: Validation failure (0)" using shaders

Question

I'm trying to move away from using glVertex() in my game code because it doesn't seem to work well with a large quantity of vertices. At the moment I'm trying to make code that uses Shaders, but when compiling with shaders.compileProgram, it gives me the error shown in the title, with no explanation as to what is wrong.

Code so far:

import OpenGL
from OpenGL.GL import *
from OpenGL.GL import shaders
from OpenGL.arrays import vbo

import math
import pygame
from pygame.locals import *

VERTEX_SHADER = shaders.compileShader("""
#version 120 
 void main() {
    gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
 }
""", GL_VERTEX_SHADER)

FRAGMENT_SHADER = shaders.compileShader("""
#version 120 
void main() { 
    gl_FragColor = vec4( 0, 1, 0, 1 ); 
}
""", GL_FRAGMENT_SHADER)

self.shader = shaders.compileProgram(VERTEX_SHADER,FRAGMENT_SHADER)

The full error message:

Traceback (most recent call last):
  File "PyOpenGl shader test from scratch.py", line 24, in <module>
    self.shader = shaders.compileProgram(VERTEX_SHADER,FRAGMENT_SHADER)
  File "/home/[my name]/.local/lib/python2.7/site-packages/OpenGL    /GL/shaders.py", line 196, in compileProgram
    program.check_validate()
  File "/home/[my name]/.local/lib/python2.7/site-packages/OpenGL/GL/shaders.py", line 108, in check_validate
    glGetProgramInfoLog( self ),
RuntimeError: Validation failure (0): 

Is there a line I need to add for it to tell me what is wrong?

Answer 1

This often happens also if you do not specify the context before compiling the shaders. For example, for QT Widgets (pytqt) you should have your shaders compiled when the gl context is enabled, for example in the initializeGL function. So in the case of using QT you can do something like:

class MyQtWidget(QOpenGLWidget, QWidget):
    def __init__(self, directory):
        super(MyQtWidget, self).__init__()
...

def initializeGL(self):
    """
    Initializes openGL context and scenery
    """
    self.shader = compileProgram(
            compileShader(my_vert_shader, gl.GL_VERTEX_SHADER),
            compileShader(my_frag_shader, gl.GL_FRAGMENT_SHADER)
        )

As for your case, please see the example from here:
https://github.com/tartley/opengl-tutorials/blob/master/pyopengl/05-lighting.py
Shaders are compiled after the context has been enabled (via the inheritance of BaseContext class).

Another example with the use of glfw also initializes the context beforehand:
https://github.com/totex/PyOpenGL_tutorials/blob/master/main.py
So in here we have this glfw.make_context_current function.

However, even if you do the above, this does not mean that your shaders are correct, but if you do intialize the context, you should get a verbose error message on what is wrong with your shaders.

Answer 2

Well, it turns out that I've just completely missed the fact that this tutorial uses a special library specifically for the tutorial. (I hate when a tutorial does this... How am I supposed to do anything without the tutorial module?)

This is the tutorial in question.

It doesn't even appear that the problem was with the shaders, I was just missing functions from an inherited class.