Rendering my first triangle with Modern OpenGL

Question

I want to use modern OpenGL to render my first triangle. (I'm using SFML) I have 2 classes:

global

, where I use this to initialize global sfml variables etc. (not relevant to my problem)

#ifndef GLOBAL_H
#define GLOBAL_H

#include <SFML/OpenGL.hpp>
#include <SFML/Graphics.hpp>
#include <SFML/Window.hpp>
#include <glm/glm.hpp>

using namespace std;

extern sf::Event Event;
extern sf::Shader defaultShader;
extern sf::ContextSettings settings;
extern sf::Window window;

void initShader();

#endif // GLOBAL_H

and

Model

This loads an obj file loader. I generated it using Blender. Here is it:

#ifndef MODEL_H
#define MODEL_H

#include <GL/glew.h>
#include "global.h"

struct Vertex{
    float x,y,z;
    Vertex(){};
    Vertex(float a,float b,float c){x=a;y=b;z=c;};
};

struct TextureCoordinate{
    float x;
    float y;
    TextureCoordinate(){};
    TextureCoordinate(float a,float b){x=a;y=b;};
};

struct FaceTexture{
    string texture;
    int vertex[3];
};

class Model
{
    public:
        Model();
        vector<Vertex> vertices;
        vector<FaceTexture> faces;
        vector<TextureCoordinate> textureCoordinates;
        vector<Vertex> normals;
        void loadModel(const char *fileName);
        void setupMesh();
        void draw();
    private:
        GLuint VAO, VBO;
};

#endif // MODEL_H

And the cpp:

#include "Model.h"

Model::Model()
{

}

void Model::loadModel(const char *fileName)
{
    int i;
    vector<string>line;
    vector<string>tmp;
    vector<int>V1;vector<int>V2;vector<int>V3;vector<int>T1;vector<int>T2;vector<int>T3;vector<int>N1;vector<int>N2;vector<int>N3;
    vector<TextureCoordinate>tc;
    vector<Vertex>nc;
    ifstream fin(fileName);
    char aux[200],matFileName[200];
    float v1,v2,v3,t1,t2,t3,n1,n2,n3;
    while(!fin.eof())
    {
        fin.getline(aux,256);
        line.push_back(aux);
    }
    fin.close();

    sscanf(line[2].c_str(),"mtllib %s",&matFileName);
    fin.open(("models/"+string("matFileName")).c_str());
    while(!fin.eof())
    {
        fin.getline(aux,200);
        tmp.push_back(aux);
    }
    ///***///
    for(i=3;i<line.size();i++)
    {
        char matName[100];
        if(line[i][0]=='v'&& line[i][1]==' ')
        {
            Vertex v;
            sscanf(line[i].c_str(),"v %f %f %f",&v.x,&v.y,&v.z);
            vertices.push_back(v);
            continue;
        }
        if(line[i][0]=='v'&&line[i][1]=='t')
        {
            TextureCoordinate t;
            sscanf(line[i].c_str(),"vt %f %f",&t.x,&t.y);
            textureCoordinates.push_back(t);
            continue;
        }
        if(line[i][0]=='v'&&line[i][1]=='n')
        {
            Vertex v;
            sscanf(line[i].c_str(),"vn %f %f %f",&v.x,&v.y,&v.z);
            normals.push_back(v);
            continue;
        }
        if(line[i][0]=='u'&&line[i][1]=='s'&&line[i][2]=='e')
        {
            sscanf(line[i].c_str(),"usemtl %s",&matName);
            continue;
        }
        if(line[i][0]=='f'&&line[i][1]==' ')
        {
            FaceTexture f;
            sscanf(line[i].c_str(),"f %d/%d/%d %d/%d/%d %d/%d/%d ",&v1,&v2,&v3,&t1,&t2,&t3,&n1,&n2,&n3);
            f.texture=matName;
            faces.push_back(f);
            V1.push_back(v1);V2.push_back(v2);V3.push_back(v3);
            T1.push_back(t1);T2.push_back(t2);T3.push_back(t3);
            N1.push_back(n1);N2.push_back(n2);N3.push_back(n3);
            continue;
        }
    }
    tc.resize(vertices.size());
    nc.resize(vertices.size());
    textureCoordinates.resize(vertices.size());
    normals.resize(vertices.size());
    for(i=0;i<faces.size();i++)
    {
        tc[V1[i]]=textureCoordinates[T1[i]];
        nc[V1[i]]=normals[N1[i]];
        tc[V2[i]]=textureCoordinates[T2[i]];
        nc[V2[i]]=normals[N2[i]];
        tc[V3[i]]=textureCoordinates[T3[i]];
        nc[V3[i]]=normals[N3[i]];
    }
    for(i=0;i<vertices.size();i++)
    {
        textureCoordinates[i]=tc[i];
        normals[i]=nc[i];
    }
    for(i=0;i<faces.size();i++)
    {
        faces[i].vertex[0]=V1[i];
        faces[i].vertex[1]=V2[i];
        faces[i].vertex[2]=V3[i];
    }
    setupMesh();
}

void Model::setupMesh()
    {
        glGenBuffers(1, & VBO);
        glBindVertexArray(VAO);
        glBindBuffer(GL_ARRAY_BUFFER,  VBO);
        glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), &vertices[0], GL_STATIC_DRAW);
        glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (GLvoid*)0);
        glEnableVertexAttribArray(0);
        glBindBuffer(GL_ARRAY_BUFFER, 0);
        glBindVertexArray(0);
    }

void Model::draw()
{
    glBindVertexArray(VAO);
    glDrawArrays(GL_TRIANGLES, 0, 3);
    glBindVertexArray(0);
}

The vertex shader:

#version 330 core

layout (location = 0) in vec3 position;
//layout (location = 1) in vec3 color;

out vec3 ourColor;

void main()
{
    ourColor=vec3(1,0,0);
    gl_Position = vec4(position, 1.0f);
    //ourColor = color;
}

And the frag shader:

#version 330 core

in vec3 ourColor;

out vec4 color;

void main()
{
    color = vec4(ourColor, 1.0f);
}

Main.cpp:

#include <GL/glew.h>
#include <global.h>

#include "Model.h"

using namespace std;

Model model;

int main()
{
    glewInit();
    initShader();

    glEnable(GL_DEPTH_TEST);
    model.loadModel("models/1/cube.obj");

    sf::Shader::bind(&defaultShader);
    while (window.isOpen())
    {
        glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
        while (window.pollEvent(Event))
        {
            if (Event.type == sf::Event::Closed)
                window.close();
        }
        model.draw();
        window.display();
    }
    return 0;
}

Why is the program showing me a black screen? The program works fine when I use old functions (glBegin,glEnd)

Answer 1

You use the variable VAO without initializing it or creating a VAO. You will have to call

glGenVertexArrays(1, &VAO);

to get a valid vertex array.

Edit 1

Next Problem: The size of data you push to the VBO is wrong

glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), &vertices[0], GL_STATIC_DRAW);

sizeof(vertices) is in this case equal to sizeof(vector<Vertex>) which is the size the vector object has in memory and not the size of the vector's data. What you want is

glBufferData(GL_ARRAY_BUFFER, sizeof(Vertex) * vertices.size(), &vertices[0], GL_STATIC_DRAW);