loading.cpp

model_t load_obj_mesh(std::string filepath)
{
    Assimp::Importer importer;

    auto importFlags = aiProcess_Triangulate | aiProcess_JoinIdenticalVertices | aiProcess_SortByPType;
    const aiScene* scene = importer.ReadFile(filepath.c_str(), importFlags);

    if (!scene)
        throw std::exception("Obj import failed.");

    model_t model;

    std::vector<float> vertex_buffer_data;
    std::vector<index_t> index_buffer_data;
    prepare_mesh_data(scene, model, vertex_buffer_data, index_buffer_data);

    model.vao.bind();

    model.vbo.bind();
    std::size_t stride = (3 + (scene->mMeshes[0]->HasNormals() > 0 ? 3 : 0) + (scene->mMeshes[0]->HasTextureCoords(0) > 0 ? 2 : 0)) * sizeof(float);
    char* offset = nullptr;

    gl::BufferData(gl::ARRAY_BUFFER, vertex_buffer_data.size() * sizeof(float), vertex_buffer_data.data(), gl::STATIC_DRAW);
    gl::EnableVertexAttribArray(0);
    gl::VertexAttribPointer(0, 3, gl::FLOAT, gl::FALSE_, stride, offset);
    offset += 3 * sizeof(float);

    if (scene->mMeshes[0]->HasNormals() > 0)
    {
        gl::EnableVertexAttribArray(1);
        gl::VertexAttribPointer(1, 3, gl::FLOAT, gl::FALSE_, stride, offset);
        offset += 3 * sizeof(float);
    }

    if (scene->mMeshes[0]->HasTextureCoords(0) > 0)
    {
        gl::EnableVertexAttribArray(2);
        gl::VertexAttribPointer(2, 2, gl::FLOAT, gl::FALSE_, stride, offset);
    }

    model.ebo.bind();
    gl::BufferData(gl::ELEMENT_ARRAY_BUFFER, index_buffer_data.size() * sizeof(index_t), index_buffer_data.data(), gl::STATIC_DRAW);

    model.vao.unbind();
    return model;
}

someshader.glsl

#version 440 core

#include "vs_common.h"
#include "basic_shader_common.glsl"

layout (location = 0) in vec3 position;
//layout (location = 1) in vec3 normal;
layout (location = 2) in vec2 texcoord;

out VertexOut
{
    vec2 texcoord;
} Out;

void main()
{
    gl_Position = modelViewProjMat * vec4(position, 1.0);
    Out.texcoord = texcoord;
}