Why my triangle is white? - c++

Question

I am fallowing this tutorial http://learnopengl.com/#!Getting-started/Hello-Triangle and problem with this tutorials is that there is no full code example, and it's little hard to fallow. My code run successful, but my triangle is blank / white. And I think some functions is called twice, and program still can run successful if I delete some of that commands.
// SHADERS
GLuint VBO;
GLuint VAO = 0;
GLuint program;
GLuint vertexShader;
GLuint fragmentShader;
const char* vertexShaderSource =
"#version 330"
"layout (location = 0) in vec3 position;"
"void main(){"
"gl_Position = vec4(position.x, position.y, position.z, 1.0);"
"}";
const char* fragmentShaderSource =
"#version 330"
"out vec4 color;"
"void main(){"
"color = vec4(1.0, 0.5, 1.0, 1.0);"
"}";
void compileShaders() {
vertexShader = glCreateShader(GL_VERTEX_SHADER); // pravi vertex shader
glShaderSource(vertexShader, 1, &vertexShaderSource, NULL); // Odredjuje izvor vertex shadera
glCompileShader(vertexShader); // kompajlira shader
fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(vertexShader, 1, &fragmentShaderSource, NULL);
glCompileShader(fragmentShader);
}
void linkShaders() {
program = glCreateProgram(); // pravi program ID
// Linkuje shaderse i program
glAttachShader(program, vertexShader);
glAttachShader(program, fragmentShader);
glLinkProgram(program);
glUseProgram(program); // koristi program
// Brise shaderse jer vise nisu potrebni i tako oslobadja memoriju
glDeleteShader(vertexShader);
glDeleteShader(fragmentShader);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(GLfloat), (GLvoid*)0);
glEnableVertexAttribArray(0); // MISLIM DA JE OVO VISAK
}
void initVBO() {
GLfloat vertices[] = {
-0.5f, -0.5f, 0.0f,
0.5f, -0.5f, 0.0f,
0.0f, 0.5f, 0.0f
};
glGenBuffers(1, &VBO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
}
void initVAO() {
glGenVertexArrays(1, &VAO);
glBindVertexArray(VAO);
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, NULL);
}
void Init() {
glClearColor(0.20, 0.63, 0.67, 1.0);
glViewport(0, 0, WIDTH, HEIGHT);
compileShaders();
linkShaders();
}
void Render() {
glClear(GL_COLOR_BUFFER_BIT);
initVAO();
initVBO();
glUseProgram(program);
glBindVertexArray(VAO);
glDrawArrays(GL_TRIANGLES, 0, 3);
glBindVertexArray(0); // oslobadja momoriju
glutSwapBuffers();
}

Answer 1

Your shaders shouldn't compile. As a result, you don't have a valid program. Depending on the profile of the GL context - and the actual GL implementation - you will get different results. With nvidia drivers, you will typically see a white triangle in that scenario.
The reason why your shaders are invalid is because you forgot to add a newline \n after the #version 330 directive.
You are using C/C++'s syntax for concatenating strings by combining "string1" "string2". The fact that you have a newline outside of the quotes is totally irrelevant, the string you are specifying is
#version 330layout (location = 0) in vec3 position;[...]
all in one line, and that is not a valid preprocessor statement...
You always should check the compile status of your shaders, and the link status of your program. And you should always query the compiler and linker info logs. Have a look at the OpenGL wiki artice about shader compilation for details of how to do that.