我有一个使用GLFW和GLEW渲染三角形的基本OpenGL程序。
我正在将Mac和Xcode用于GLFW 3.3和GLEW 2.1。
我遇到glfwCreateWindow()的问题，如果我将OpenGL配置文件设置为核心配置文件（由于我理解Mac需要它），它将返回null，并且我通过将向前兼容性设置为true来解决了该问题。
有人可以向我解释此解决方案是否正确吗？
另一件事是，现在创建窗口时没有问题，但是现在我在屏幕上看不到任何东西。
这是代码：
#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <iostream>
static unsigned int CompileShader(unsigned int type, const std::string& source)
{
unsigned int id = glCreateShader(type);
const char* src = source.c_str();
glShaderSource(id, 1, &src, nullptr);
// Compiles the actual shader
glCompileShader(id);
// Error handeling of the compilation
int result;
glGetShaderiv(id, GL_COMPILE_STATUS, &result);
if (result == GL_FALSE)
{
int length;
// Gets the lenght of the message
glGetShaderiv(id, GL_INFO_LOG_LENGTH, &length);
// This is used to allocate memory on the stack dynamically
char* message = (char*)alloca(length * sizeof(char));
// Gets the log
glGetShaderInfoLog(id, length, &length, message);
std::cout << "Failed to compile " << (type == GL_VERTEX_SHADER ? "vertex" : "fragment") << std::endl;
std::cout << message << std::endl;
glDeleteShader(id);
return 0;
}
return id;
}
static unsigned int CreateShader(const std::string& vertexShader, const std::string& fragmentShader)
{
unsigned int program = glCreateProgram();
// Creating the two shader
unsigned int vs = CompileShader(GL_VERTEX_SHADER, vertexShader);
unsigned int fs = CompileShader(GL_FRAGMENT_SHADER, fragmentShader);
// Attaches the two shaders to the program and validate everything
glAttachShader(program, vs);
glAttachShader(program, fs);
glLinkProgram(program); // This links the shader executable to the actual processor
glValidateProgram(program);
glDeleteShader(vs);
glDeleteShader(fs);
return program;
}
int main(void)
{
// to initialize glew go to c++ preprocessor and add GLEW_STATIC
GLFWwindow* window;
/* Initialize the library */
if (!glfwInit())
return -1;
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 2);
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
/* Create a window and its OpenGl context */
window = glfwCreateWindow(640, 480, "Hello World", NULL, NULL);
if (!window)
{
glfwTerminate();
return -1;
}
/* Make the window's context current */
glfwMakeContextCurrent(window);
// Glew init HAS to be put after making the context
if (glewInit() != GLEW_OK)
std::cout << "GlewInit Error" << std::endl;
std::cout << "VERSION:" << std::endl;
std::cout << glGetString(GL_VERSION) << std::endl;
std::cout << "GL Version: " << (char *)glGetString(GL_SHADING_LANGUAGE_VERSION) << std::endl;
// Defining the position of the vertices
float positions[6] = {
-0.5f, -0.5f,
0.0f, 0.5f,
0.5f, -0.5f
};
unsigned int buffer;
glGenBuffers(1, &buffer);
glBindBuffer(GL_ARRAY_BUFFER, buffer);
glBufferData(GL_ARRAY_BUFFER, 6 * sizeof(float), positions, GL_STATIC_DRAW);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, sizeof(float) * 2, 0);
std::string vertexShader =
"#version 330 core\n"
"\n"
// here we are saying that the attribute at the position 0 (see attribPointer)
// which is the position itself is a input value put in a vec4 because
// glPosition needs a vec4
"layout(location = 0) in vec4 position;\n"
"\n"
"void main()\n"
"{\n"
" gl_Position = position;\n"
"}\n";
std::string fragmentShader =
"#version 330 core\n"
"\n"
"layout(location = 0) out vec4 color;\n"
"\n"
"void main()\n"
"{\n"
" color = vec4(1.0, 0.0, 0.0, 1.0);\n"
"}\n";
unsigned int shader = CreateShader(vertexShader, fragmentShader);
glUseProgram(shader);
/* Loop until the user closes the window */
while (!glfwWindowShouldClose(window))
{
/* Render here */
glClear(GL_COLOR_BUFFER_BIT);
// second parameter is the starting index and the third is the number of indexes
glDrawArrays(GL_TRIANGLES, 0, 3);
/* Swap front and back buffers */
glfwSwapBuffers(window);
/* Poll for and process events */
glfwPollEvents();
}
glDeleteProgram(shader);
glfwTerminate();
return 0;
}
答案 0 :(得分：1)
Vertex Array Objects (VAOs)在Core上下文中不是可选的，就像它们在Compatibility中一样。您必须要画一个任何东西。
创建一个并绑定它，然后设置顶点布局和图形：
GLuint vao = 0;
glCreateVertexArrays( 1, &vao );
glBindVertexArray( vao );
...
glEnableVertexAttribArray( ... );
glVertexAttribPointer( ... );
...
glDrawArrays( ... );
一起：
#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <iostream>
#include <cstdarg>
struct Program
{
static GLuint Load( const char* shader, ... )
{
GLuint prog = glCreateProgram();
va_list args;
va_start( args, shader );
while( shader )
{
const GLenum type = va_arg( args, GLenum );
AttachShader( prog, type, shader );
shader = va_arg( args, const char* );
}
va_end( args );
glLinkProgram( prog );
CheckStatus( prog );
return prog;
}
private:
static void CheckStatus( GLuint obj )
{
GLint status = GL_FALSE;
if( glIsShader(obj) ) glGetShaderiv( obj, GL_COMPILE_STATUS, &status );
if( glIsProgram(obj) ) glGetProgramiv( obj, GL_LINK_STATUS, &status );
if( status == GL_TRUE ) return;
GLchar log[ 1 << 15 ] = { 0 };
if( glIsShader(obj) ) glGetShaderInfoLog( obj, sizeof(log), NULL, log );
if( glIsProgram(obj) ) glGetProgramInfoLog( obj, sizeof(log), NULL, log );
std::cerr << log << std::endl;
std::exit( EXIT_FAILURE );
}
static void AttachShader( GLuint program, GLenum type, const char* src )
{
GLuint shader = glCreateShader( type );
glShaderSource( shader, 1, &src, NULL );
glCompileShader( shader );
CheckStatus( shader );
glAttachShader( program, shader );
glDeleteShader( shader );
}
};
const char* vert = 1 + R"GLSL(
#version 330 core
// here we are saying that the attribute at the position 0 (see attribPointer)
// which is the position itself is a input value put in a vec4 because
// glPosition needs a vec4
layout(location = 0) in vec4 position;
void main()
{
gl_Position = position;
};
)GLSL";
const char* frag = 1 + R"GLSL(
#version 330 core
layout(location = 0) out vec4 color;
void main()
{
color = vec4(1.0, 0.0, 0.0, 1.0);
};
)GLSL";
int main( void )
{
if( !glfwInit() )
return -1;
glfwWindowHint( GLFW_CONTEXT_VERSION_MAJOR, 3 );
glfwWindowHint( GLFW_CONTEXT_VERSION_MINOR, 3 );
glfwWindowHint( GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE );
glfwWindowHint( GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE );
GLFWwindow* window = glfwCreateWindow( 640, 480, "Hello World", NULL, NULL );
if( !window )
{
glfwTerminate();
return -1;
}
glfwMakeContextCurrent( window );
// Glew init HAS to be put after making the context
if( glewInit() != GLEW_OK )
std::cout << "GlewInit Error" << std::endl;
GLuint vao = 0;
glCreateVertexArrays( 1, &vao );
glBindVertexArray( vao );
// Defining the position of the vertices
float positions[ 6 ] = {
-0.5f, -0.5f,
0.0f, 0.5f,
0.5f, -0.5f
};
unsigned int buffer;
glGenBuffers( 1, &buffer );
glBindBuffer( GL_ARRAY_BUFFER, buffer );
glBufferData( GL_ARRAY_BUFFER, 6 * sizeof( float ), positions, GL_STATIC_DRAW );
glEnableVertexAttribArray( 0 );
glVertexAttribPointer( 0, 2, GL_FLOAT, GL_FALSE, sizeof( float ) * 2, 0 );
GLuint shader = Program::Load( vert, GL_VERTEX_SHADER, frag, GL_FRAGMENT_SHADER, NULL );
glUseProgram( shader );
while( !glfwWindowShouldClose( window ) )
{
glClear( GL_COLOR_BUFFER_BIT );
glDrawArrays( GL_TRIANGLES, 0, 3 );
glfwSwapBuffers( window );
glfwPollEvents();
}
glDeleteProgram( shader );
glfwTerminate();
return 0;
}