I'm new to OpenGL and try to learn OpenGL 4 by following the http://www.openglbook.com tutorial.
On page two, we create a simple triangle using shaders. But right after creating the vertex shader, the program crashes. By Debugging, I could find a OpenGL error GL_INVALID_ENUM
(0x0500). See code below...
Unfrotunately I couldn't find any solution. Maybe you know sth?
Edit:
So, after searching again for GL_INVALID_ENUM
and glewInit()
, I found that there are already many posts on other Websites, BUT:
Most of them had some typos in their shaders and I definitely don't. On
http://www.opengl.org/wiki/OpenGL_Loading_Library
i found:
You might still get GL_INVALID_ENUM (depending on the version of GLEW you use), but at least GLEW ignores glGetString(GL_EXTENSIONS) and gets all function pointers.
Some recommend to just ignore the error, but I still can't run the program... Btw, could anyone of you try to run the program? If you had the same error, we'd definitely know it's not a wrong IDE/Project configuration of mine.
Specs:
Windows 8.1 64bit
Intel Core i7-3517U with
Intel HD4000 GPU (OpenGL 4.0.0 Support)
8 GB RAM
IDE:
Eclipse IDE for C/C++ Developers
Version: Kepler Service Release 1
Build id: 20130919-0819
using MinGW Compiler
code:
#include <stdlib.h>
#include <stdio.h>
#include <string>
#define GLEW_STATIC
#include <gl/glew.h>
#include <gl/freeglut.h>
#define WINDOW_TITLE_PREFIX "Chapter 2"
// initialization
int CurrentWidth = 800,
CurrentHeight = 600,
WindowHandle = 0;
// timer
unsigned FrameCount = 0;
// chapter2 buffer object.........................
GLuint VertexShaderId,
FragmentShaderId,
ProgramId,
VaoId,
VboId,
ColorBufferId;
const GLchar *VertexShader = {
"#version 400\n"\
"layout(location=0) in vec4 in_Position;\n"\
"layout(location=1) in vec4 in_Color;\n"\
"out vec4 ex_Color;\n"\
"void main(void) {\n"\
" gl_Position = in_Position;\n"\
" ex_Color = in_Color;\n"\
"}\n"
};
const GLchar *FragmentShader = {
"#version 400\n"\
"in vec4 ex_Color;\n"\
"out vec4 out_Color;\n"\
"void main(void) {\n"\
" out_Color = ex_Color;\n"\
"}\n"
};
//................................chapter2 buffer object
// initialization
void Initialize(int,char*[]);
void InitWindow(int,char*[]);
void ResizeFunction(int,int);
void RenderFunction(void);
//timer
void TimerFunction(int);
void IdleFunction(void);
// chapter2 buffer object
void Cleanup(void);
void CreateVBO(void);
void DestroyVBO(void);
void CreateShaders(void);
void DestroyShaders(void);
int main(int argc, char *argv[]) {
fprintf(stdout,"Starting OpenGL programm...\n");
Initialize(argc,argv);
glutMainLoop();
fprintf(stdout,"Program terminated.\n");
exit(EXIT_SUCCESS);
}
void Initialize(int argc, char *argv[]) {
GLenum GlewInitResult; //glew
InitWindow(argc,argv);
//glew...........
GlewInitResult = glewInit();
if(GLEW_OK != GlewInitResult) {
fprintf(stderr,
"ERROR: %s\n",
glewGetErrorString(GlewInitResult) );
exit(EXIT_FAILURE);
}
//.................glew.
fprintf(stdout,
"INFO: OpenGL Version: %s\n",
glGetString(GL_VERSION) );
//chapter2 buffer objects
CreateShaders();
CreateVBO();
glClearColor(0.0f,0.0f,0.0f,0.0f);
}
void InitWindow(int argc, char *argv[]) {
glutInit(&argc,argv); // always the first function to call!!!
glutInitContextVersion(4,0);
glutInitContextFlags(GLUT_FORWARD_COMPATIBLE);
glutInitContextProfile(GLUT_CORE_PROFILE);
glutSetOption(GLUT_ACTION_ON_WINDOW_CLOSE,
GLUT_ACTION_GLUTMAINLOOP_RETURNS);
glutInitWindowSize(CurrentWidth,CurrentHeight);
glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA);
WindowHandle = glutCreateWindow(WINDOW_TITLE_PREFIX);
if(WindowHandle < 1) {
fprintf(stderr,
"ERROR: Could not create a new rendering window.\n");
exit(EXIT_FAILURE);
}
glutReshapeFunc(ResizeFunction);
glutDisplayFunc(RenderFunction);
//timer
glutIdleFunc(IdleFunction);
glutTimerFunc(0,TimerFunction,0);
//chapter2 buffer object
glutCloseFunc(Cleanup);
}
void ResizeFunction(int Width, int Height) {
CurrentWidth = Width;
CurrentHeight = Height;
glViewport(0,0,CurrentWidth,CurrentHeight);
}
void RenderFunction() {
//timer
++FrameCount;
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
//chapter2 buffer object
glDrawArrays(GL_TRIANGLES,0,3);
glutSwapBuffers();
glutPostRedisplay();
}
//timer.................................
void IdleFunction() {
glutPostRedisplay();
}
void TimerFunction(int Value) {
if(0 != Value) {
char *TempString = (char*) malloc(512 + strlen(WINDOW_TITLE_PREFIX));
sprintf(TempString,
"%s: %d Frames Per Second @ %d x %d",
WINDOW_TITLE_PREFIX,
FrameCount * 4,
CurrentWidth,
CurrentHeight );
glutSetWindowTitle(TempString);
free(TempString);
}
FrameCount = 0;
glutTimerFunc(250,TimerFunction,1);
}
//...........................................timer
//chapter2 buffer object..................................
void Cleanup() {
DestroyShaders();
DestroyVBO();
}
void CreateVBO() {
GLfloat Vertices[] = {
-0.8f, -0.8f, 0.0f, 1.0f,
0.0f, 0.8f, 0.0f, 1.0f,
0.8f, -0.8f, 0.0f, 1.0f
};
GLfloat Colors[] = {
1.0f, 0.0f, 0.0f, 1.0f,
0.0f, 1.0f, 0.0f, 1.0f,
0.0f, 0.0f, 1.0f, 1.0f
};
GLenum ErrorCheckValue = glGetError();
glGenVertexArrays(1,&VaoId);
glBindVertexArray(VaoId);
glGenBuffers(1,&VboId);
glBindBuffer(GL_ARRAY_BUFFER, VboId);
glBufferData(GL_ARRAY_BUFFER, sizeof(Vertices), Vertices, GL_STATIC_DRAW);
glVertexAttribPointer(0,4,GL_FLOAT, GL_FALSE, 0,0);
glEnableVertexAttribArray(0);
glGenBuffers(1,&ColorBufferId);
glBindBuffer(GL_ARRAY_BUFFER, ColorBufferId);
glBufferData(GL_ARRAY_BUFFER, sizeof(Colors), Colors, GL_STATIC_DRAW);
glVertexAttribPointer(1,4,GL_FLOAT, GL_FALSE, 0,0);
glEnableVertexAttribArray(1);
ErrorCheckValue = glGetError();
if(ErrorCheckValue != GL_NO_ERROR) {
fprintf(stderr,
"ERROR: Could not create a VBO: %s \n",
gluErrorString(ErrorCheckValue) );
exit(-1);
}
}
void DestroyVBO() {
GLenum ErrorCheckValue = glGetError();
glDisableVertexAttribArray(1);
glDisableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER,0);
glDeleteBuffers(1, &ColorBufferId);
glDeleteBuffers(1, &VboId);
glBindVertexArray(0);
glDeleteVertexArrays(1,&VaoId);
ErrorCheckValue = glGetError();
if(ErrorCheckValue != GL_NO_ERROR) {
fprintf(stderr,
"ERROR: Could not destroy the VBO: %s \n",
gluErrorString(ErrorCheckValue) );
exit(-1);
}
}
void CreateShaders() {
GLenum ErrorCheckValue = glGetError();
VertexShaderId = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(VertexShaderId,1,&VertexShader,NULL);
glCompileShader(VertexShaderId);
FragmentShaderId = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(FragmentShaderId,1,&FragmentShader,NULL);
glCompileShader(FragmentShaderId);
ProgramId = glCreateProgram();
glAttachShader(ProgramId, VertexShaderId);
glAttachShader(ProgramId, FragmentShaderId);
glLinkProgram(ProgramId);
if(glIsProgram(ProgramId) != GL_TRUE) {
fprintf(stderr,
"ERROR: This is no GL program!\n");
exit(-1);
}
glUseProgram(ProgramId);
ErrorCheckValue = glGetError();
if(ErrorCheckValue != GL_NO_ERROR) {
fprintf(stderr,
"ERROR: Could not create the shaders: %s \n",
gluErrorString(ErrorCheckValue) );
exit(-1);
}
}
void DestroyShaders() {
GLenum ErrorCheckValue = glGetError();
glUseProgram(0);
glDetachShader(ProgramId, VertexShaderId);
glDetachShader(ProgramId, FragmentShaderId);
glDeleteShader(FragmentShaderId);
glDeleteShader(VertexShaderId);
glDeleteProgram(ProgramId);
ErrorCheckValue = glGetError();
if(ErrorCheckValue != GL_NO_ERROR) {
fprintf(stderr,
"ERROR: Could not destroy the VBO: %s \n",
gluErrorString(ErrorCheckValue) );
exit(-1);
}
}
I could finally solve the problem: First of all, I did severel minor changes, so I can not tell you, if it was just one change or the sum of all, what solved it.
glu
library.
I had to link this library to use gluErrorString(...)
. Replace this function with glewGetErrorString(...)
. Now you don't need the glu
library anymore.glutInitContextVersion(4,0);
. I can't tell you really why - probably glew
doesn't support the new OpenGL 4 functions.That's it. I hope this helps (I found the same problem on several other Websites)! And thanks for your advices :)
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