问题描述
我最近开始关注TheCherno在youtube上的OpenGL教程系列。
这是我的代码：
#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <iostream>
#include <fstream>
#include <string>
#include <sstream>
struct ShaderProgramSource {
std::string VertexSource;
std::string FragmentSource;
};
static ShaderProgramSource ParseShader(const std::string& filepath) {
std::ifstream stream(filepath);
enum class ShaderType {
NONE = -1,VERTEX = 0,FRAGMENT = 1
};
std::string line;
std::stringstream ss[2];
ShaderType type = ShaderType::NONE;
while (getline(stream,line)) {
if (line.find("#shader") != std::string::npos) {
if (line.find("vertex") != std::string::npos)
type = ShaderType::VERTEX;
else if (line.find("fragment") != std::string::npos)
type = ShaderType::FRAGMENT;
} else {
ss[(int)type] << line << '\n';
}
}
return { ss[0].str(),ss[1].str() };
}
static unsigned int CompileShader(unsigned int type,const std::string& source) {
std::cout << "Compiling " << (type == GL_VERTEX_SHADER ? "vertex" : "fragment") << " shader..." << std::endl;
unsigned int id = glCreateShader(type);
const char* src = source.c_str();
glShaderSource(id,1,&src,nullptr);
std::cout << glGetError() << std::endl;
glCompileShader(id);
std::cout << glGetError() << std::endl;
int result;
glGetShaderiv(id,GL_COMPILE_STATUS,&result);
std::cout << glGetError() << std::endl;
if (result == GL_FALSE) {
int length;
glGetShaderiv(id,GL_INFO_LOG_LENGTH,&length);
std::cout << glGetError() << std::endl;
char* message = (char*)alloca(length * sizeof(char));
glGetShaderInfoLog(id,length,&length,message);
std::cout << glGetError() << std::endl;
std::cout << "Failed to compile" << (type == GL_VERTEX_SHADER ? "vertex" : "fragment") << " shader!" << std::endl;
std::cout << message << std::endl;
glDeleteShader(id);
std::cout << glGetError() << std::endl;
return 0;
}
std::cout << "Successfully compiled " << (type == GL_VERTEX_SHADER ? "vertex" : "fragment") << " shader!" << std::endl << std::endl;
return id;
}
static unsigned int CreateShader(const std::string& vertexShader,const std::string& fragmentShader) {
std::cout << "Creating shader..." << std::endl << std::endl;
unsigned int program = glCreateProgram();
unsigned int vs = CompileShader(GL_VERTEX_SHADER,vertexShader);
unsigned int fs = CompileShader(GL_FRAGMENT_SHADER,fragmentShader);
glAttachShader(program,vs);
std::cout << glGetError() << std::endl;
std::cout << "Attached vertex shader" << std::endl;
glAttachShader(program,fs);
std::cout << glGetError() << std::endl;
std::cout << "Attached fragment shader" << std::endl;
glLinkProgram(program);
std::cout << glGetError() << std::endl;
glValidateProgram(program);
std::cout << glGetError() << std::endl;
std::cout << "Linked and validated program" << std::endl;
glDeleteShader(vs);
std::cout << glGetError() << std::endl;
std::cout << "Deleted vertex shader" << std::endl;
glDeleteShader(fs);
std::cout << glGetError() << std::endl;
std::cout << "Deleted fragment shader" << std::endl;
std::cout << "Succesfully created shader!" << std::endl << std::endl;
return program;
}
int main(void)
{
GLFWwindow* window;
/* Initialize the library */
if (!glfwInit())
return -1;
/* Create a windowed mode 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);
if (glewInit() != GLEW_OK) {
std::cout << "Error!" << std::endl;
}
std::cout << glGetString(GL_VERSION) << std::endl;
float positions[6] = {
-0.5f,-0.5f,0.0f,0.5f,-0.5f
};
unsigned int buffer;
glGenBuffers(1,&buffer);
std::cout << glGetError() << std::endl;
glBindBuffer(GL_ARRAY_BUFFER,buffer);
std::cout << glGetError() << std::endl;
glBufferData(GL_ARRAY_BUFFER,6*sizeof(float),positions,GL_STATIC_DRAW);
std::cout << glGetError() << std::endl;
gldisabLevertexAttribArray(0);
std::cout << glGetError() << std::endl;
glVertexAttribPointer(0,2,GL_FLOAT,GL_FALSE,sizeof(float)*2,0);
std::cout << glGetError() << std::endl;
glBindBuffer(GL_ARRAY_BUFFER,0);
std::cout << glGetError() << std::endl;
ShaderProgramSource source = ParseShader("res/shaders/Basic.shader");
std::cout << "VERTEX" << std::endl;
std::cout << source.VertexSource << std::endl;
std::cout << "FRAGMENT" << std::endl;
std::cout << source.FragmentSource << std::endl;
//unsigned int shader = CreateShader(vertexShader,fragmentShader);
///gluseProgram(shader);
// render loop
while (!glfwWindowShouldClose(window))
{
/* Render here */
glClear(GL_COLOR_BUFFER_BIT);
glDrawArrays(GL_TRIANGLES,3);
/* Swap front and back buffers */
glfwSwapBuffers(window);
/* Poll for and process events */
glfwPollEvents();
}
//glDeleteProgram(shader);
glfwTerminate();
return 0;
}
这是Basic.shader文件：
#shader vertex
#version 330 core
layout(location = 0) in vec4 position;
void main()
{
gl_Position = position;
}
#shader fragment
#version 330 core
layout(location = 0) out vec4 color;
void main()
{
color = vec4(1.0,0.0,1.0);
}
解决方法
您需要启用通用顶点属性数组而不是禁用它（请参见glEnableVertexAttribArray）：
glDisableVertexAttribArray(0);
glEnableVertexAttribArray(0);
此外，将编译，链接和安装sahder的代码注释掉：
//unsigned int shader = CreateShader(vertexShader,fragmentShader); ///glUseProgram(shader);
unsigned int shader = CreateShader(source.VertexSource,source.FragmentSource);
glUseProgram(shader);
我相信@ Rabbid76的答案是正确的。如果仍然无法使用，请确保您使用兼容的OpenGL上下文或创建VAO来保存状态。
兼容的OpenGL上下文可以设置为：
//Before glfwCreateWindow call,after glfwInit
glfwWindowHint(GLFW_OPENGL_PROFILE,GLFW_OPENGL_COMPAT_PROFILE);
默认值为GLFW_OPENGL_ANY_PROFILE，如果CORE不可用，则可能表示COMPAT。这样可以确保默认VAObject始终存在并已绑定。这意味着您的glVertexAttribPointer呼叫实际上有一个存储该信息的地方。我没有看到这些Cherno的教程，将来的教程中很有可能涵盖了VAO。在CORE中将没有一个，并且可能不会绘制任何内容。
虽然我们在这里，但精确设置所需的最小 OpenGL版本并不是一个坏主意。如果由于某种原因在目标计算机上不可用，则窗口创建将失败。这比在调用不受支持的函数时出现“随机”段错误更可取。
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR,3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR,3);
我的首选方式是创建一个实际的VAO并使用GLFW_OPENGL_CORE_PROFILE。但是请随意阅读教程，我从他那里看到的教程确实非常高质量。
//Put these before the vertex buffer initialization
int VAO;
glGenVertexArrays(1,&VAO);
glBindVertexArray(VAO);