OpenGL "black screen" when rendering "vertex colored" triangle using shader

Question

I'm very new to OpenGL and have been following this really simple tutorial where I'm supposed to create a vertex-colored triangle (the tutorial in question).

Although, my result just comes out as a black screen. I've tried completly copying his code but it still doesn't work, which leads me to belive the tutorial is out of date.

I've tried removing the "#version 130" in the shaders but that did nothing. I've also debugged the render function and it is indeed being called. I don't know what could be wrong.

This is my code:

main.cpp

#ifdef _WIN32
#define _CRT_SECURE_NO_DEPRECATE
#endif

#include <GL\glew.h>
#include <GL\freeglut.h>
#include <stdio.h>

#define BUFFER_OFFSET(i) ((char *)NULL + (i))
GLuint shaderProgramID;
GLuint vao = 0;
GLuint vbo;
GLuint positionID, colorID;

#pragma region SHADER_FUNCTIONS
static char* readFile(const char* filename) {
    //Open the file
    FILE* fp = fopen(filename, "r");
    //Move to the end of file
    fseek(fp, 0, SEEK_END);
    long file_length = ftell(fp);
    fseek(fp, 0, SEEK_SET);
    char* contents = new char[file_length + 1];
    //zero out memory
    for (int i = 0; i < file_length + 1; i++) {
        contents[i] = 0;
    }
    //Read file
    fread(contents, 1, file_length, fp);
    //Denote end
    contents[file_length + 1] = '\0';
    fclose(fp);
    return contents;
}

GLuint makeVertexShader(const char* shaderSource) {
    GLuint vertexShaderID = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertexShaderID, 1, (const GLchar**)&shaderSource, NULL);
    glCompileShader(vertexShaderID);
    return vertexShaderID;
}

GLuint makeFragmentShader(const char* shaderSource) {
    GLuint fragmentShaderID = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragmentShaderID, 1, (const GLchar**)&shaderSource, NULL);
    glCompileShader(fragmentShaderID);
    return fragmentShaderID;
}

GLuint makeShaderProgram(GLuint vertexShaderID, GLuint fragmentShaderID) {
    GLuint shaderID = glCreateProgram();
    glAttachShader(shaderID, vertexShaderID);
    glAttachShader(shaderID, fragmentShaderID);
    glLinkProgram(shaderID);
    return shaderID;
}
#pragma endregion

void changeViewport(int w, int h) {
    glViewport(0, 0, w, h);
}

void render() {
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glDrawArrays(GL_TRIANGLES, 0, 3);
    glutSwapBuffers();
    printf("Debug");
}

int main(int argc, char** argv) {
    //Init GLUT
    glutInit(&argc, argv);

    //Set up some memory buffers for our display
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH);
    //Set up window size
    glutInitWindowSize(800, 600);
    //Create window
    glutCreateWindow("Project 1");
    //Bind the two functions to respond when necessary
    glutReshapeFunc(changeViewport);
    glutDisplayFunc(render);

    //Initialize OpenGL driver
    GLenum err = glewInit();
    if (GLEW_OK != err) {
        fprintf(stderr, "GLEW error");
        return 1;
    }

    //Vertices and colors of trangle
    GLfloat vertices[] = {
        -0.5f, -0.5f, 0.0f,
        0.5f, -0.5f, 0.0f,
        0.0f,-0.5f, 0.0f
    };
    GLfloat colors[] = {
        1.0f, 0.0f, 0.0f, 1.0f,
        0.0f, 1.0f, 0.0f, 1.0f,
        0.0f, 0.0f, 1.0f, 1.0f
    };

    #pragma region MAKE_SHADER
    char* vertexShaderSourceCode = readFile("vertexShader.vs");
    char* fragmentShaderSourceCode = readFile("fragmentShader.fs");
    GLuint vertShaderID = makeVertexShader(vertexShaderSourceCode);
    GLuint fragShaderID = makeFragmentShader(fragmentShaderSourceCode);
    GLuint shaderProgramID = makeShaderProgram(vertShaderID, fragShaderID);

    printf("vertShaderID is %d\n", vertShaderID);
    printf("fragmentShaderID is %d\n", fragShaderID);
    printf("shaderProgramID is %d\n", shaderProgramID);
    #pragma endregion

    //Create the "remember-all"
    glGenVertexArrays(1, &vao);
    glBindVertexArray(vao);

    glGenBuffers(1, &vbo);
    glBindBuffer(GL_ARRAY_BUFFER, vbo);
    //Create buffer
    glBufferData(GL_ARRAY_BUFFER, 7 * 3 * sizeof(GLfloat), NULL, GL_STATIC_DRAW);
    //Load the vertex points
    glBufferSubData(GL_ARRAY_BUFFER, 0, 3 * 3 * sizeof(GLfloat), vertices);
    //Load the colors
    glBufferSubData(GL_ARRAY_BUFFER, 3 * 3 * sizeof(GLfloat), 3 * 4 * sizeof(GLfloat), colors);

    //Find variables in shader
    positionID = glGetAttribLocation(shaderProgramID, "s_vPosition");
    colorID = glGetAttribLocation(shaderProgramID, "s_vColor");

    glVertexAttribPointer(positionID, 3, GL_FLOAT, GL_FALSE, 0, 0);
    glVertexAttribPointer(colorID, 4, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(3 * 3 * sizeof(GLfloat)));
    glUseProgram(shaderProgramID);
    glEnableVertexAttribArray(positionID);
    glEnableVertexAttribArray(colorID);

    //Start up a loop that runs in the background
    glutMainLoop();
    return 0;
}

fragmentShader.fs

#version 130

in vec4 color;
out vec4 fColor;

void main () {
    fColor = color;
}

vertexShader.vs

#version 130

in vec4 s_vPosition;
in vec4 s_vColor;
out vec4 color;

void main () {
    //gl_Position = s_mP*s_mV*s_mM*s_vPosition;
    color = s_vColor;
    gl_Position = s_vPosition;
}

Answer 1

Ughh, I'm sorry for creating this. After sleeping and looking through my code again I realized that all my vertices had the same "y value".

GLfloat vertices[] = {
   -0.5f, -0.5f, 0.0f,
    0.5f, -0.5f, 0.0f,
    0.0f, -0.5f, 0.0f
};

Anyway, It's solved. And god do i feel stupid.