UV Instancing

InstanceTest.cpp

#include <SFML/Window.hpp>

#include "shader.hpp"

#include <iostream>

//list of triangles points
const float tris[] = 
{
    -0.75,0.0,
    0.0,0.0,
    0.0,0.75,
    -0.75,-0.25,
    0.0,-0.5,
    -0.75,-0.75,
    0.25,-0.75,
    0.5,0.5,
    0.75,-0.75
};

float uvs[] =
{
    0.0, 0.0,
    0.5, 0.0,
    1.0, 1.0
};

int main()
{
    sf::ContextSettings contextSettings;
    contextSettings.majorVersion = 3;
    contextSettings.minorVersion = 3;
    contextSettings.stencilBits = 8;

    sf::Window window(sf::VideoMode(640,640),"Instancing Test", sf::Style::Default, contextSettings);
    window.setActive(true);

    if(!gladLoadGL())
    {
        std::cout<<"Failed to initialize GLAD"<<std::endl;
        return -1;
    }

    GLuint vao;
    glGenVertexArrays(1, &vao);

    GLuint vertexBuffer, uvBuffer;
    glGenBuffers(1, &vertexBuffer);
    glGenBuffers(1, &uvBuffer);

    glBindVertexArray(vao);

    glBindBuffer(GL_ARRAY_BUFFER, uvBuffer);
    glBufferData(GL_ARRAY_BUFFER, sizeof(uvs), uvs, GL_STATIC_DRAW);
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0,2,GL_FLOAT,GL_FALSE,2*sizeof(float),nullptr);

    glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
    glBufferData(GL_ARRAY_BUFFER, sizeof(tris), tris, GL_STATIC_DRAW);
    glEnableVertexAttribArray(1);
    glVertexAttribPointer(1,2,GL_FLOAT,GL_FALSE,2*sizeof(float),nullptr);

    glVertexAttribDivisor(0,0);
    glVertexAttribDivisor(1,1);

    glBindVertexArray(0);

    GLuint program = compileProgram("filledBezVert.glsl","filledBezFrag.glsl");

    glClearColor(0.0f,0.1f,0.1f,1.0f);

    bool isRunning = true;
    while (isRunning)
    {
        glClear(GL_COLOR_BUFFER_BIT);
//it works... something to do with the shader then !!!
        glUseProgram(program);
        glBindVertexArray(vao);
//        glDrawArrays(GL_TRIANGLES,0,3);//what?
        glDrawArraysInstanced(GL_TRIANGLES,0,3,9);//3 instances
        glBindVertexArray(0);
        glUseProgram(0);

        window.display();

        sf::Event event;
        window.waitEvent(event);
        if(event.type == sf::Event::Closed)
            isRunning = false;
    }
    
    window.close();

    return 0;
}