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Geometrian

OpenGL OpenGL Errors

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Geometrian    1810
Hi, I use PyOpenGL. Recently, it seems to not be reporting OpenGL errors. I created the brief following test file, which doesn't throw errors for me, but does for everybody else:
import OpenGL, logging
logging.basicConfig()
OpenGL.ERROR_CHECKING = True
OpenGL.ERROR_LOGGING = True
##OpenGL.FULL_LOGGING = True
OpenGL.ERROR_ON_COPY = True
from OpenGL.GL import *
from OpenGL.GLU import *
import sys,os
import pygame
from pygame.locals import *
pygame.init()

Screen = (800,600)
pygame.display.set_mode(Screen,OPENGL|DOUBLEBUF)
    
def quit(): pygame.quit(); sys.exit()

def GetInput():
    for event in pygame.event.get():
        if event.type == QUIT: quit()
        if event.type == KEYDOWN:
            if event.key == K_ESCAPE: quit()
def Draw():
    glLoadIdentity()

    glViewport(0,0,-800,-600)

##    glBegin(GL_QUADS)
##    glClear(GL_DEPTH_BUFFER_BIT)
##    glEnd()
    
    pygame.display.flip()
def main():
    Clock = pygame.time.Clock()
    while True:
        GetInput()
        Draw()
        Clock.tick(60)
##        Clock.tick()
##        print "fps: %f" % round(Clock.get_fps(),2)
if __name__ == '__main__': main()
Just to make sure that the error really was in PyOpenGL, I created the following C++ OpenGL application from a basic example, found here: (adding a check error and a glViewport(0,0,-800,-600) statement:
//
// GLSAMPLE.CPP
//  by Blaine Hodge
//

// Includes

#include <windows.h>
#include <gl/gl.h>

// Function Declarations

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam);
void EnableOpenGL(HWND hWnd, HDC * hDC, HGLRC * hRC);
void DisableOpenGL(HWND hWnd, HDC hDC, HGLRC hRC);

// WinMain

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, 
				   LPSTR lpCmdLine, int iCmdShow)
{
	WNDCLASS wc;
	HWND hWnd;
	HDC hDC;
	HGLRC hRC;
	MSG msg;
	BOOL quit = FALSE;
	float theta = 0.0f;
	
	// register window class
	wc.style = CS_OWNDC;
	wc.lpfnWndProc = WndProc;
	wc.cbClsExtra = 0;
	wc.cbWndExtra = 0;
	wc.hInstance = hInstance;
	wc.hIcon = LoadIcon( NULL, IDI_APPLICATION );
	wc.hCursor = LoadCursor( NULL, IDC_ARROW );
	wc.hbrBackground = (HBRUSH)GetStockObject( BLACK_BRUSH );
	wc.lpszMenuName = NULL;
	wc.lpszClassName = "GLSample";
	RegisterClass( &wc );
	
	// create main window
	hWnd = CreateWindow( 
		"GLSample", "OpenGL Sample", 
		WS_CAPTION | WS_POPUPWINDOW | WS_VISIBLE,
		0, 0, 256, 256,
		NULL, NULL, hInstance, NULL );
	
	// enable OpenGL for the window
	EnableOpenGL( hWnd, &hDC, &hRC );
	
	// program main loop
	while ( !quit )
	{
		
		// check for messages
		if ( PeekMessage( &msg, NULL, 0, 0, PM_REMOVE )  )
		{
			
			// handle or dispatch messages
			if ( msg.message == WM_QUIT ) 
			{
				quit = TRUE;
			} 
			else 
			{
				TranslateMessage( &msg );
				DispatchMessage( &msg );
			}
			
		} 
		else 
		{
			
			// OpenGL animation code goes here
			
			glClearColor( 0.0f, 0.0f, 0.0f, 0.0f );
			glClear( GL_COLOR_BUFFER_BIT );
			glViewport(0,0,-800,-600);
			GLenum output = glGetError();
			
			glPushMatrix();
			glRotatef( theta, 0.0f, 0.0f, 1.0f );
			glBegin( GL_TRIANGLES );
			glColor3f( 1.0f, 0.0f, 0.0f ); glVertex2f( 0.0f, 1.0f );
			glColor3f( 0.0f, 1.0f, 0.0f ); glVertex2f( 0.87f, -0.5f );
			glColor3f( 0.0f, 0.0f, 1.0f ); glVertex2f( -0.87f, -0.5f );
			glEnd();
			glPopMatrix();
			
			SwapBuffers( hDC );
			
			theta += 1.0f;
			
		}
		
	}
	
	// shutdown OpenGL
	DisableOpenGL( hWnd, hDC, hRC );
	
	// destroy the window explicitly
	DestroyWindow( hWnd );
	
	return msg.wParam;
	
}

// Window Procedure

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	
	switch (message)
	{
		
	case WM_CREATE:
		return 0;
		
	case WM_CLOSE:
		PostQuitMessage( 0 );
		return 0;
		
	case WM_DESTROY:
		return 0;
		
	case WM_KEYDOWN:
		switch ( wParam )
		{
			
		case VK_ESCAPE:
			PostQuitMessage(0);
			return 0;
			
		}
		return 0;
	
	default:
		return DefWindowProc( hWnd, message, wParam, lParam );
			
	}
	
}

// Enable OpenGL

void EnableOpenGL(HWND hWnd, HDC * hDC, HGLRC * hRC)
{
	PIXELFORMATDESCRIPTOR pfd;
	int format;
	
	// get the device context (DC)
	*hDC = GetDC( hWnd );
	
	// set the pixel format for the DC
	ZeroMemory( &pfd, sizeof( pfd ) );
	pfd.nSize = sizeof( pfd );
	pfd.nVersion = 1;
	pfd.dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER;
	pfd.iPixelType = PFD_TYPE_RGBA;
	pfd.cColorBits = 24;
	pfd.cDepthBits = 16;
	pfd.iLayerType = PFD_MAIN_PLANE;
	format = ChoosePixelFormat( *hDC, &pfd );
	SetPixelFormat( *hDC, format, &pfd );
	
	// create and enable the render context (RC)
	*hRC = wglCreateContext( *hDC );
	wglMakeCurrent( *hDC, *hRC );
	
}

// Disable OpenGL

void DisableOpenGL(HWND hWnd, HDC hDC, HGLRC hRC)
{
	wglMakeCurrent( NULL, NULL );
	wglDeleteContext( hRC );
	ReleaseDC( hWnd, hDC );
}
Using a simple breakpoint to check "output" returns the number 1244832 the first time it's called and then 0's on subsequent frames. I'm very unfamiliar with OpenGL in C/C++ environments, but I'm fairly certain these results mean OpenGL's error checking is not working. I'm not sure why this would be. My best guess would be that I somehow have disabled my card's OpenGL error reporting. I seem to remember an option for it somewhere in my card's control panel--but I cannot seem to find it. Of course, I could be going in the completely wrong direction, in which case, I hope you can enlighten me. Ideas/help/comments? Thanks a lot, -Geometrian

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karwosts    840
That sounds very bizarre. I've never heard of being able to disable error reporting on a gpu, but I don't know for sure if that is possible or not.

Not sure I can explain your error code, I've never seen a code like that. Typical GL error codes I think are around ~1280, never seen anything that is 7 digits.

My only idea is to maybe try to pass your error code to gluErrorString? That might give more information:


const GLubyte* gluErrorString(GLenum errorCode);

"-Returns a pointer to a descriptive string that corresponds to the OpenGL or GLU error number passed in errorCode."

Wish I had a better explanation.

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Geometrian    1810
I think the 7-digit think may have been just a debugging fluke. I tried:

const GLubyte *output1 = gluErrorString(glGetError());
glViewport(0,0,-800,-600);
const GLubyte *output2 = gluErrorString(glGetError());

On the first frame, both output1 and output2 are weird strings of apparently random characters. On the second and subsequent frames, each return a no error.

Hmmmmmm . . .

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