我正在学习OpenGL,所以我正在尝试绘制2D图像。首先,将所有内容放入C ++程序的主要功能中。工作正常(绘制了2个三角形)。
我决定通过制作单独的类来使程序更清晰,但是...现在它不再起作用了。当我要制作OpenGL上下文时,它会失败。当我显示错误时,我得到:
Failed creating OpenGL context at version requested
在本教程中,我正在阅读,他们说这个错误最有可能是由于您的图形卡不支持OpenGL版本,但是如果是这种情况,那么当我将所有代码都放入其中时,它将不起作用主要程序。
这是出错的部分(上下文创建):
bool OpenGL_Scene::initializeWindow() {
// Initialize the SDL
if(SDL_Init(SDL_INIT_VIDEO) < 0)
{
cout << "Error while initializing the SDL : " << SDL_GetError() << endl;
SDL_Quit();
return false;
}
// Configure OpenGL
// Use version 3.1
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3); // OpenGL 3.x
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 1); // OpenGL x.1 --> OpenGL 3.1
// Double buffering
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1); // Use double buffering (0 to not use it)
SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24); // Buffer has a depth of 24 bits
// Make the window
this->window = SDL_CreateWindow(this->windowTitle.c_str(), SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, this->windowWidth, this->windowHeight, SDL_WINDOW_SHOWN | SDL_WINDOW_OPENGL); // SDL_WINDOW_OPENGL necessary to specify that the window will have an OpenGL context attached to it.
if(this->window == 0) // Initialization failed
{
cout << "Error while creating the window : " << SDL_GetError() << endl;
SDL_Quit();
return false;
}
// Make the OpenGL context given the SDL window
this->OpenGL_Context = SDL_GL_CreateContext(this->window);
// Make sure the creation of the context succeeded. If not the problem is probably that the version of OpenGL isn't supported by the graphics card.
if(this->OpenGL_Context == 0)
{
cout << "Could not create the OpenGL context : " << SDL_GetError() << endl;
SDL_DestroyWindow(window);
SDL_Quit();
return false;
}
return true;
};
在最后几行中显示错误,因此程序导致:
Could not create the OpenGL context : Failed creating OpenGL context at version requested
我进行了很多搜索以找到解决方案,然后找到了这个:SO主题
因此,在上面的代码中,我尝试了:
// Configure OpenGL
// Use version 3.1
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3); // OpenGL 3.x
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 1); // OpenGL x.1 --> OpenGL 3.1
// Double buffering
SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE); // ADDING THIS AVOIDS THAT THE CONTEXT COULD NOT BE CREATED BUT THEN WHEN WE DRAW SOMETHING WE DON'T SEE ANYTHING
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1); // Use double buffering (0 to not use it)
SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24); // Buffer has a depth of 24 bits
现在,当我使用此额外的行运行程序时,将创建上下文(没有错误OpenGL_Context != 0
),但是没有绘制任何内容。我省略了我正在绘制的代码部分,因为该代码以前可以工作,并且我没有做任何更改。
有人知道可能是什么问题吗?
PS:我正在使用Macbook Pro(OS X Yosemite(10.10.4)),并且我的图形卡是NVIDIA GeForce GT 650M 1024 MB
编辑:我尝试调试绘制三角形的代码,但我确实看不到错误(主要是因为我真的是OpenGL的新手)。在下面可以找到绘图代码。请注意,由于不再需要,我不再初始化GLEW(根据评论)。
void OpenGL_Scene::mainLoop() {
bool end = false;
// Make vertices (punten) in a table
// !!! WARNING : Use 1 table for ALL vertices !!! Don't use a separate table for each of the forms, this would slow down the program because you have to send each of the tables to OpenGL !!!
float vertices[] = {-0.5, -0.5, 0.0, 0.5, 0.5, -0.5, // 3 Points for first triangle --> (-0.5, -0.5) , (0.0, 0.5) and (0.5, -0.5) (All in (x, y) --> 2D)
-0.8, -0.8, -0.3, -0.8, -0.8, -0.3}; // 3 Points for second triangle
// Before we start drawing, clear the screen
glClear(GL_COLOR_BUFFER_BIT);
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, vertices);
glEnableVertexAttribArray(0); // Activate the table we passed to OpenGL using the identifier (index) passed to OpenGL (in this case 0)
// Now that OpenGL knows which vertices it has to display we are going to specify what it has to do with these vertices
glDrawArrays(GL_TRIANGLES, 0, 6); // Draw both triangles
glDisableVertexAttribArray(0); // Because it isn't necessary anymore
SDL_GL_SwapWindow(this->window); // Refresh the screen
while(!end) {
// Listen to events and play with them
SDL_WaitEvent(&this->events); // Will wait for an event and assign it to "events" variable
if(this->events.window.event == SDL_WINDOWEVENT_HIDDEN)
cout << "The user has hidden the window !" << endl;
else if(this->events.window.event == SDL_WINDOWEVENT_CLOSE) {
cout << "The user closed the window !" << endl;
glClear(GL_COLOR_BUFFER_BIT); // Clear the screen
SDL_GL_SwapWindow(this->window); // Refresh the window
end = true;
}
}
// Quitting the SDL and OpenGL properly is done by the destructor
}
因此,现在执行项目时,首先创建窗口(成功),然后调用mainLoop
过程(从上方)。我使用调试器跨过绘图代码,所有过程都被调用(glClear,...),但是窗口中什么都没有出现(它保持黑色)。
我发现了错误。在初始化SDL之后,我正在初始化OpenGL,这就是为什么在不强制进入“ Core Profile”的情况下无法创建上下文的原因。
“ initializeWindow”中的正确顺序为:
// Configure OpenGL
// Use version 3.1
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3); // OpenGL 3.x
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 1); // OpenGL x.1 --> OpenGL 3.1
// Double buffering
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1); // Use double buffering (0 to not use it)
SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24); // Buffer has a depth of 24 bits
// Initialize the SDL
if(SDL_Init(SDL_INIT_VIDEO) < 0)
{
cout << "Error while initializing the SDL : " << SDL_GetError() << endl;
SDL_Quit();
return false;
}
这样做可以成功创建上下文。
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