backend_ogl.cpp

//
// backend_ogl.cpp -- opengl graphics backend.
// Copyright (C) 2020, Voxelius team.
//
#include <voxelius/debug.h>
#include "graphics/backend_ogl.h"

void VxOpenGlGraphicsBackend::Init(SDL_Window *pWindow)
{
    m_pWindow = pWindow;
    m_glContext = SDL_GL_CreateContext(m_pWindow);
    Vx_AssertMsg(m_glContext != nullptr, "Failed to create OpenGL context.");

    SDL_GL_MakeCurrent(m_pWindow, m_glContext);
    GLenum result = glewInit();
    Vx_AssertMsg(result = GLEW_OK, "GLEW initialization failure.");
}

void VxOpenGlGraphicsBackend::Shutdown(void)
{
    for(const auto &it : m_meshes) {
        glDeleteBuffers(1, &it.second.m_ebo);
        glDeleteBuffers(1, &it.second.m_vbo);
        glDeleteVertexArrays(1, &it.second.m_vao);
    }
    m_meshes.clear();

    for(const auto &it : m_textures)
        glDeleteTextures(1, &it.second);
    m_textures.clear();

    SDL_GL_DeleteContext(m_glContext);
    m_pWindow = nullptr;
}

void VxOpenGlGraphicsBackend::LoadTexture(const VxImage &data, unsigned int &id)
{
    Vx_AssertMsg(m_pWindow && m_glContext, "Backend is not initialized.");
    unsigned int tex;

    glGenTextures(1, &tex);
    glBindTexture(GL_TEXTURE_2D, tex);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);	
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, data.GetWidth(), data.GetHeight(), 0, GL_RGBA, GL_UNSIGNED_BYTE, data.GetPixels());
    glBindTexture(GL_TEXTURE_2D, 0);

    id = m_textureIndex++;
    m_textures[id] = tex;
}

void VxOpenGlGraphicsBackend::UpdateTexture(unsigned int id, const VxImage &data)
{
    Vx_AssertMsg(m_pWindow && m_glContext, "Backend is not initialized.");

    const auto &it = m_textures.find(id);
    Vx_AssertMsg(it != m_textures.cend(), "Invalid texture handle.");

    glBindTexture(GL_TEXTURE_2D, it->second);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);	
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, data.GetWidth(), data.GetHeight(), 0, GL_RGBA, GL_UNSIGNED_BYTE, data.GetPixels());
    glBindTexture(GL_TEXTURE_2D, 0);
}

void VxOpenGlGraphicsBackend::BindTexture(unsigned int id)
{
    Vx_AssertMsg(m_pWindow && m_glContext, "Backend is not initialized.");

    const auto &it = m_textures.find(id);
    Vx_AssertMsg(it != m_textures.cend(), "Invalid texture handle.");

    glBindTexture(GL_TEXTURE_2D, it->second);
}

void VxOpenGlGraphicsBackend::UnbindTexture(void)
{
    Vx_AssertMsg(m_pWindow && m_glContext, "Backend is not initialized.");

    glBindTexture(GL_TEXTURE_2D, 0);
}

void VxOpenGlGraphicsBackend::UnloadTexture(unsigned int id)
{
    Vx_AssertMsg(m_pWindow && m_glContext, "Backend is not initialized.");

    const auto &it = m_textures.find(id);
    Vx_AssertMsg(it != m_textures.cend(), "Invalid texture handle.");

    glDeleteTextures(1, &it->second);
    m_textures.erase(it);
}

void VxOpenGlGraphicsBackend::LoadMesh(const VxMesh &mesh, unsigned int &id)
{
    Vx_AssertMsg(m_pWindow && m_glContext, "Backend is not initialized.");

    VxOpenGlMesh_t glMesh;
    glGenVertexArrays(1, &glMesh.m_vao);
    glGenBuffers(1, &glMesh.m_vbo);
    glGenBuffers(1, &glMesh.m_ebo);

    glBindVertexArray(glMesh.m_vao);

    glBindBuffer(GL_ARRAY_BUFFER, glMesh.m_vbo);
    glBufferData(GL_ARRAY_BUFFER, (GLsizeiptr)(mesh.GetVerticesCount() * sizeof(VxVertex)), mesh.GetVertices(), GL_STATIC_DRAW);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, glMesh.m_ebo);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, (GLsizeiptr)(mesh.GetIndicesCount() * sizeof(unsigned int)), mesh.GetIndices(), GL_STATIC_DRAW);

    // These will automatically be at:
    // layout(location = 0) in dvec3 g_position;
    // layout(location = 1) in dvec3 g_normal;
    // layout(location = 2) in dvec2 g_tcoord;
    // layout(location = 3) in dvec4 g_color;
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0, 3, GL_DOUBLE, GL_FALSE, sizeof(VxVertex), (void *)offsetof(VxVertex, m_position));
    glEnableVertexAttribArray(1);
    glVertexAttribPointer(1, 3, GL_DOUBLE, GL_FALSE, sizeof(VxVertex), (void *)offsetof(VxVertex, m_normal));
    glEnableVertexAttribArray(2);
    glVertexAttribPointer(2, 2, GL_DOUBLE, GL_FALSE, sizeof(VxVertex), (void *)offsetof(VxVertex, m_tcoord));
    glEnableVertexAttribArray(3);
    glVertexAttribPointer(3, 4, GL_DOUBLE, GL_FALSE, sizeof(VxVertex), (void *)offsetof(VxVertex, m_color));

    glBindVertexArray(0);

    id = m_meshIndex++;;
    m_meshes[id] = glMesh;
}

void VxOpenGlGraphicsBackend::UpdateMesh(unsigned int id, const VxMesh &mesh)
{
    Vx_AssertMsg(m_pWindow && m_glContext, "Backend is not initialized.");

    const auto &it = m_meshes.find(id);
    Vx_AssertMsg(it != m_meshes.cend(), "Invalid mesh handle.");

    VxOpenGlMesh_t &glMesh = it->second;
    glBindVertexArray(glMesh.m_vao);

    glBindBuffer(GL_ARRAY_BUFFER, glMesh.m_vbo);
    glBufferData(GL_ARRAY_BUFFER, (GLsizeiptr)(mesh.GetVerticesCount() * sizeof(VxVertex)), mesh.GetVertices(), GL_STATIC_DRAW);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, glMesh.m_ebo);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, (GLsizeiptr)(mesh.GetIndicesCount() * sizeof(unsigned int)), mesh.GetIndices(), GL_STATIC_DRAW);

    glBindVertexArray(0);
}

void VxOpenGlGraphicsBackend::UnloadMesh(unsigned int id)
{
    Vx_AssertMsg(m_pWindow && m_glContext, "Backend is not initialized.");

    const auto &it = m_meshes.find(id);
    Vx_AssertMsg(it != m_meshes.cend(), "Invalid mesh handle.");

    glDeleteBuffers(1, &it->second.m_ebo);
    glDeleteBuffers(1, &it->second.m_vbo);
    glDeleteVertexArrays(1, &it->second.m_vao);
    m_meshes.erase(it);
}