OpenGL drawing Triangles only white - c++

Question

I try learing OpenGL with those two tutorials:
https://learnopengl.com/#!Getting-started/Hello-Triangle and
https://www.youtube.com/playlist?list=PLEETnX-uPtBXT9T-hD0Bj31DSnwio-ywh
When I draw a simple triangle it is only white. But the code seems right.
This is the fragment Shader:
#version 330 core
out vec4 fragColor;
void main()
{
fragColor = vec4(0.5, 0.3, 0.1, 1.0);
}
This is the ShaderProgram:
ShaderProgram::ShaderProgram(std::string fileName)
{
vertexShader = glCreateShader(GL_VERTEX_SHADER);
if (vertexShader == 0)
std::cerr << "VertexShader creation failed! " << std::endl;
const char* vertexShaderSource = (SourceLoader(fileName + ".vs")).c_str();
glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
glCompileShader(vertexShader);
CheckErrorMessages(vertexShader, GL_COMPILE_STATUS, false, "VertexShader Compilation failed! ");
fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
if (fragmentShader == 0)
std::cerr << "FragmentShader Creation failed! " << std::endl;
const char* fragmentShaderSource = (SourceLoader(fileName + ".fs")).c_str();
glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
glCompileShader(fragmentShader);
CheckErrorMessages(fragmentShader, GL_COMPILE_STATUS, false, "FragmentShader Compilation failed! ");
program = glCreateProgram();
glAttachShader(program, vertexShader);
glAttachShader(program, fragmentShader);
glLinkProgram(program);
CheckErrorMessages(program, GL_LINK_STATUS, true, "Program linking failed! ");
glValidateProgram(program);
CheckErrorMessages(program, GL_VALIDATE_STATUS, true, "Program validation failed! ");
}
I have three methods in the ShaderProgram class:
1. a method to load the shader code, which is definitly working.
2. a method to Check for Error Messages, which is also working.
3. and a bind() Funktion which is just using glUseProgram(program)
I also have a class for the window, which is created by SDL
Display::Display(std::string title, unsigned int width, unsigned int height)
{
SDL_GL_SetAttribute(SDL_GL_RED_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_BUFFER_SIZE, 32);
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
m_window = SDL_CreateWindow(title.c_str(), SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, width, height, SDL_WINDOW_OPENGL);
m_glcontext = SDL_GL_CreateContext(m_window);
GLenum status = glewInit();
if (status != GLEW_OK)
std::cerr << "GLEW failed to initialize!" << std::endl;
isClosed = false;
}
the Display class has a method to update and clear:
void Display::Update()
{
SDL_GL_SwapWindow(m_window);
SDL_Event e;
while (SDL_PollEvent(&e))
{
if (e.type == SDL_QUIT)
isClosed = true;
}
}
void Display::Clear(float red, float green, float blue, float alpha)
{
glClearColor(red, green, blue, alpha);
glClear(GL_COLOR_BUFFER_BIT);
}
I also have a class called Mesh to manage VAO and VBO etc.:
Mesh::Mesh(Vertex* vertices, unsigned int numVertices)
{
drawCount = numVertices;
glGenVertexArrays(1, &VAO);
glBindVertexArray(VAO);
GLuint VBO;
glGenBuffers(1, &VBO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, numVertices * sizeof(vertices[0]), vertices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(vertices[0]), (void*)0);
glEnableVertexAttribArray(0);
}
Mesh has one Funktion to draw the given vertices:
void Mesh::Draw()
{
glBindVertexArray(VAO);
glDrawArrays(GL_TRIANGLES, 0, drawCount);
glBindVertexArray(0);
}
The main Funktion consists out of a while loop:
int main(int argc, char* argv[])
{
SDL_Init(SDL_INIT_EVERYTHING);
Display display("Fenster", 1024, 840);
ShaderProgram shader("./res/Shader");
Vertex vertices[] = { Vertex(glm::vec3(1, 1, 0)), Vertex(glm::vec3(1, -1, 0)), Vertex(glm::vec3(-1, -1, 0)) };
Mesh mesh(vertices, 3);
while (!display.getIsClosed())
{
display.Clear(1.0f, 0.0f, 1.0f, 1.0f);
shader.Bind();
mesh.Draw();
display.Update();
}
SDL_Quit();
return 0;
}
The problem is I don´t get any Error, but the triangle keep staying white.
Thank you for helping!
Edit: Vertex Shader is here:
#version 330 core
layout (location = 0) in vec3 position;
void main()
{
gl_Position = vec4(position.x, position.y, position.z, 1.0);
}

Answer 1

If you check your infoLog you'd find that your shaders aren't compiling. You're assigning the shader source pointer to a temporary string that gets destroyed at the end of the line, and you're sending gibberish to the shader compiler:
const char* fragmentShaderSource = (SourceLoader(fileName + ".fs")).c_str();// After this line the pointer isn't valid
glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
SourceLoader returns a temporary string, and you assign fragmentShaderSource pointer to the string. Then there is junk data there by the time you pass it to glShaderSource. You can do:
std::string vertShaderString = SourceLoader(fileName + ".vs");
const char* vertShaderSource = vertShaderString.c_str();
glShaderSource(vertexShader, 1, &vertShaderSource, NULL);
You also need to fix the same problem for the fragment shader.
Also you drew a clockwise winding triangle, which is fine, but by default OpenGL considers counterclockwise winding as front-facing.
Another thing, the reason you didn't catch the error is because you CheckErrorMessages doesn't do anything, you should be writing the infoLog to the string or something.