I have recently taken up an online tutorial on OpenGL (TheChernoProject) and everything went pretty good until I actually started writing shaders. when I compile my code, it runs, but nothing is displayed on screen, although there should be a red triangle.
I am writing this code on MacOS 10.14.6 in a terminal. I've downloaded both glfw and glew, and am compiling code using a following command:
clang++ -framework Cocoa -framework OpenGL -framework IOKit -framework CoreVideo -lglfw -lglew main.cpp -o main.o
I've already tried replacing #version 330 core with #version 440 core, since its the latest my Mac supports, but to no avail.
here is my code:
#include <iostream>
#include <GL/glew.h>
#include <GLFW/glfw3.h>
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);
glCompileShader(id);
int result;
glGetShaderiv(id, GL_COMPILE_STATUS, &result);
if(!result){
int length;
glGetShaderiv(id, GL_INFO_LOG_LENGTH, &length);
char* message = (char*)alloca(length * sizeof(char));
glGetShaderInfoLog(id, length, &length, message);
std::cout<<"failed to compile "<<(type==GL_VERTEX_SHADER?"vertex":"fragment")<<" shader"<<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();
unsigned int vs = CompileShader(GL_VERTEX_SHADER, vertexShader);
unsigned int fs = CompileShader(GL_FRAGMENT_SHADER, fragmentShader);
glAttachShader(program, vs);
glAttachShader(program, fs);
glLinkProgram(program);
glValidateProgram(program);
glDeleteShader(vs);
glDeleteShader(fs);
return program;
}
int main(void){
GLFWwindow* window;
if(!glfwInit())return -1;
glfwWindowHint( GLFW_CONTEXT_VERSION_MAJOR, 3 );
glfwWindowHint( GLFW_CONTEXT_VERSION_MINOR, 3 );
glfwWindowHint( GLFW_OPENGL_FORWARD_COMPAT, GLFW_TRUE );
glfwWindowHint( GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE );
window = glfwCreateWindow(640, 480, "Hello World", NULL, NULL);
if (!window){
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);
if(glewInit() != GLEW_OK)return -1;
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, 2 * sizeof(float), 0);
std::string fragmentShader =
"#version 330 core\n"
"layout(location = 0) out vec4 color;\n"
"void main(){\n"
" color = vec4(1.0, 0.0, 0.0, 1.0);\n"
"}\n";
std::string vertexShader =
"#version 330 core\n"
"layout(location = 0) in vec4 position;\n"
"void main(){\n"
" gl_Position = position;\n"
"}\n";
unsigned int shader = CreateShader(vertexShader, fragmentShader);
glUseProgram(shader);
glBindBuffer(GL_ARRAY_BUFFER, 0);
while (!glfwWindowShouldClose(window)){
glClear(GL_COLOR_BUFFER_BIT);
glDrawArrays(GL_TRIANGLES, 0, 3);
glfwSwapBuffers(window);
glfwPollEvents();
}
glfwTerminate();
return 0;
}
Ripi2 has it, you need a vertex array object (VAO) bound to render anything in a Core context:
# Mesa on Linux is about as picky as Apple's OpenGL implementation :)
$ g++ `pkg-config --cflags --libs glfw3 glew` main.cpp
$ MESA_DEBUG=1 ./a.out
Mesa: User error: GL_INVALID_OPERATION in glVertexAttribPointer(no array object bound)
Mesa: User error: GL_INVALID_OPERATION in glDrawArrays(no VAO bound)
For example:
GLuint vao = 0;
glGenVertexArrays( 1, &vao );
glBindVertexArray( vao );
// glVertexAttribPointer()/glEnableVertexAttribArray()/glDraw*() calls here
All together:
#include <iostream>
#include <GL/glew.h>
#include <GLFW/glfw3.h>
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);
glCompileShader(id);
int result;
glGetShaderiv(id, GL_COMPILE_STATUS, &result);
if(!result){
int length;
glGetShaderiv(id, GL_INFO_LOG_LENGTH, &length);
char* message = (char*)alloca(length * sizeof(char));
glGetShaderInfoLog(id, length, &length, message);
std::cout<<"failed to compile "<<(type==GL_VERTEX_SHADER?"vertex":"fragment")<<" shader"<<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();
unsigned int vs = CompileShader(GL_VERTEX_SHADER, vertexShader);
unsigned int fs = CompileShader(GL_FRAGMENT_SHADER, fragmentShader);
glAttachShader(program, vs);
glAttachShader(program, fs);
glLinkProgram(program);
glValidateProgram(program);
glDeleteShader(vs);
glDeleteShader(fs);
return program;
}
int main(void){
GLFWwindow* window;
if(!glfwInit())return -1;
glfwWindowHint( GLFW_CONTEXT_VERSION_MAJOR, 3 );
glfwWindowHint( GLFW_CONTEXT_VERSION_MINOR, 3 );
glfwWindowHint( GLFW_OPENGL_FORWARD_COMPAT, GLFW_TRUE );
glfwWindowHint( GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE );
window = glfwCreateWindow(640, 480, "Hello World", NULL, NULL);
if (!window){
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);
if(glewInit() != GLEW_OK)return -1;
float positions[6] = {
-0.5f,-0.5f,
0.0f, 0.5f,
0.5f,-0.5f
};
GLuint vao = 0;
glGenVertexArrays( 1, &vao );
glBindVertexArray( vao );
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, 2 * sizeof(float), 0);
std::string fragmentShader =
"#version 330 core\n"
"layout(location = 0) out vec4 color;\n"
"void main(){\n"
" color = vec4(1.0, 0.0, 0.0, 1.0);\n"
"}\n";
std::string vertexShader =
"#version 330 core\n"
"layout(location = 0) in vec4 position;\n"
"void main(){\n"
" gl_Position = position;\n"
"}\n";
unsigned int shader = CreateShader(vertexShader, fragmentShader);
glUseProgram(shader);
glBindBuffer(GL_ARRAY_BUFFER, 0);
while (!glfwWindowShouldClose(window)){
glClear(GL_COLOR_BUFFER_BIT);
glDrawArrays(GL_TRIANGLES, 0, 3);
glfwSwapBuffers(window);
glfwPollEvents();
}
glfwTerminate();
return 0;
}