我在MacOSX 10.10上使用OpenGL和SDL2。我一直在尝试在现代OpenGL中使用VAO和VBO，但我无法让它们绘制。我的着色器非常简单，但根据教程，我一直在努力追随它们应该工作。我没有收到任何错误，但它仍然无法正常工作。我收到的只是一个完全黑色的窗户。如果有人能帮助我了解我的问题所在以及我如何解决它，我将非常感激。我希望我不会重复上一个问题，但我已经搜索过，没有找到解决这个问题的方法。这是我的代码：
vertexShader.glsl：
#version 330 core
layout(location = 0) in vec3 vertexPosition_modelspace;
void main(){
gl_Position.xyz = vertexPosition_modelspace;
gl_Position.w = 1.0;
}
fragmentShader.glsl
#version 330 core
out vec4 color;
void main(){
color = vec4(1.0, 1.0, 0.0, 1.0);
}
这是我加载着色器的代码，它已经工作并且没有提供任何错误：
//Note: PXConsole is a util class for printing to the console.
GLuint loadShaders(std::string vertexPath, std::string fragmentPath){
const char* vertexShaderPath = vertexPath.c_str();
const char* fragmentShaderPath = fragmentPath.c_str();
// Create the shaders
GLuint VertexShaderID = glCreateShader(GL_VERTEX_SHADER);
GLuint FragmentShaderID = glCreateShader(GL_FRAGMENT_SHADER);
// Read the Vertex Shader code from the file
std::string VertexShaderCode;
std::ifstream VertexShaderStream(vertexShaderPath, std::ios::in);
if(VertexShaderStream.is_open()){
std::string Line = "";
while(getline(VertexShaderStream, Line))
VertexShaderCode += "\n" + Line;
VertexShaderStream.close();
}else{
std::string error ="Could not open vertex shader at \"" + vertexPath +"\". Is the the path written correctly? ";
PXConsole::err(error);
return 0;
}
// Read the Fragment Shader code from the file
std::string FragmentShaderCode;
std::ifstream FragmentShaderStream(fragmentShaderPath, std::ios::in);
if(FragmentShaderStream.is_open()){
std::string Line = "";
while(getline(FragmentShaderStream, Line))
FragmentShaderCode += "\n" + Line;
FragmentShaderStream.close();
}else{
std::string error ="Could not open fragment shader at \"" + fragmentPath +"\". Is the the path written correctly? ";
PXConsole::err(error);
return 0;
}
GLint Result = GL_FALSE;
int InfoLogLength;
// Compile Vertex Shader
PXConsole::info("Compiling Vertex Shader at: " + vertexPath);
char const * VertexSourcePointer = VertexShaderCode.c_str();
glShaderSource(VertexShaderID, 1, &VertexSourcePointer , NULL);
glCompileShader(VertexShaderID);
// Check Vertex Shader
glGetShaderiv(VertexShaderID, GL_COMPILE_STATUS, &Result);
glGetShaderiv(VertexShaderID, GL_INFO_LOG_LENGTH, &InfoLogLength);
if ( InfoLogLength > 0 ){
std::vector<char> VertexShaderErrorMessage(InfoLogLength+1);
glGetShaderInfoLog(VertexShaderID, InfoLogLength, NULL, &VertexShaderErrorMessage[0]);
PXConsole::err(&VertexShaderErrorMessage[0]);
}
// Compile Fragment Shader
PXConsole::info("Compiling Fragment Shader at: " + fragmentPath);
char const * FragmentSourcePointer = FragmentShaderCode.c_str();
glShaderSource(FragmentShaderID, 1, &FragmentSourcePointer , NULL);
glCompileShader(FragmentShaderID);
// Check Fragment Shader
glGetShaderiv(FragmentShaderID, GL_COMPILE_STATUS, &Result);
glGetShaderiv(FragmentShaderID, GL_INFO_LOG_LENGTH, &InfoLogLength);
if ( InfoLogLength > 0 ){
std::vector<char> FragmentShaderErrorMessage(InfoLogLength+1);
glGetShaderInfoLog(FragmentShaderID, InfoLogLength, NULL, &FragmentShaderErrorMessage[0]);
PXConsole::err(&FragmentShaderErrorMessage[0]);
}
// Link the program
PXConsole::info("Linking Shader Program!");
GLuint ProgramID = glCreateProgram();
glAttachShader(ProgramID, VertexShaderID);
glAttachShader(ProgramID, FragmentShaderID);
glLinkProgram(ProgramID);
// Check the program
glGetProgramiv(ProgramID, GL_LINK_STATUS, &Result);
glGetProgramiv(ProgramID, GL_INFO_LOG_LENGTH, &InfoLogLength);
if ( InfoLogLength > 0 ){
std::vector<char> ProgramErrorMessage(InfoLogLength+1);
glGetProgramInfoLog(ProgramID, InfoLogLength, NULL, &ProgramErrorMessage[0]);
PXConsole::err(&ProgramErrorMessage[0]);
}
glDetachShader(ProgramID, VertexShaderID);
glDetachShader(ProgramID, FragmentShaderID);
glDeleteShader(VertexShaderID);
glDeleteShader(FragmentShaderID);
return ProgramID;
这是我用SDL2创建的OpenGL上下文：
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 3);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_FLAGS, SDL_GL_CONTEXT_FORWARD_COMPATIBLE_FLAG);
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);
appWindow = SDL_CreateWindow("Window Title", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 1280, 720, SDL_WINDOW_OPENGL);
if (!application->appWindow) {
PXConsole::err("Couldn't Initialize Window!!");
endApp();
}
appGLContext = SDL_GL_CreateContext(appWindow);
最后这是我的渲染函数循环：
void render(){
GLuint vaoID;
GLuint posVBO;
GLfloat positions[] = {-0.5f, -0.5f, 1.0f,
0.5f, -0.5f, 1.0f,
0.5f, 0.5f, 1.0f,
-0.5f, 0.5f, 1.0f};
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
//shaderProgramID = the function mentioned above in an initializating function and has no errors finding the shader files
glUseProgram(shaderProgramID);
glColor4f(1.0, 1.0, 0.0, 1.0);
glGenVertexArrays(1, &vaoID);
glBindVertexArray(vaoID);
glGenBuffers(1, &posVBO);
glBindBuffer(GL_ARRAY_BUFFER, posVBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(positions), positions, GL_STATIC_DRAW);
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, posVBO);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);
glColor4f(1.0, 0.0, 0.0, 1.0);
glDrawArrays(GL_QUADS, 0, 4);
glDisableVertexAttribArray(0);
SDL_GL_SwapWindow(appWindow);
}
我希望有足够的代码来确定问题。谢谢你的帮助！
答案 0 :(得分：1)
VAO基本上存储由glVertexAttribPointer设置的属性绑定。为了存储它们，必须在VAO绑定时设置它们。在您的情况下，首先解除绑定，然后设置属性绑定。
此外，应该从不在每个帧中生成缓冲区或vaos。这是必须在初始化期间完成的事情。
由于您在问题中说您没有收到任何错误：每个框架中至少有三个错误。你如何检查错误？
glColor4f已从OpenGL 3.3 Core Profile中删除。调用此方法应该会导致错误。 （2×）GL_QUADS在核心配置文件中不是有效的drawing mode，也应该生成错误。更正版本可能如下所示
初始化
glGenVertexArrays(1, &vaoID);
glBindVertexArray(vaoID);
glGenBuffers(1, &posVBO);
glBindBuffer(GL_ARRAY_BUFFER, posVBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(positions), positions, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);
glEnableVertexAttribArray(0);
渲染
glBindVertexArray(vaoID);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
<强>更新
如果要在每个帧中使用新坐标，仍然会生成缓冲区并在初始化中设置VAO。你在每一帧中做的是将新数据上传到缓冲区（假设顶点的数量保持不变）：
glBindBuffer(GL_ARRAY_BUFFER, posVBO);
glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(positions), positions);
这将覆盖缓冲区的数据而不分配新的GPU内存。请注意，您必须在初始化时使用正确的大小调用glBufferData一次，但使用nullptr作为数据指针来为缓冲区分配内存。