terrain-gen/src/skybox.cpp

#include "skybox.h"

SkyBox::SkyBox(GLsizei resolution): m_resolution(resolution)
{

}

SkyBox::~SkyBox()
{
    glDeleteVertexArrays(1, &m_vao);
    glDeleteBuffers(1, &m_vbo);
    glDeleteTextures(1, &m_textureId);
}

void SkyBox::initGl(Shader* program)
{
    initializeOpenGLFunctions();

    m_program = program;

    glGenBuffers(1, &m_vbo);
    glGenVertexArrays(1, &m_vao);

    int locationPos = m_program->attributeLocation("in_position");

    loadMesh();

    glBindVertexArray(m_vao);
        glBindBuffer(GL_ARRAY_BUFFER, m_vbo);
            glVertexAttribPointer(GLuint(locationPos), 3, GL_FLOAT, GL_FALSE, 0, reinterpret_cast<void *>(0));
            glEnableVertexAttribArray(GLuint(locationPos));
        glBindBuffer(GL_ARRAY_BUFFER, 0);
    glBindVertexArray(0);

    glGenTextures(1, &m_textureId);

    QTime t;
    t.start();
    qDebug() << "Generating skybox...";
    generateCubeMap();
    qDebug() << "Skybox generated in" << t.elapsed() / 1000.f << "s";
}

void SkyBox::generateCubeMap() {
    GLuint fbo;
    glGenFramebuffers(1, &fbo);
    glBindFramebuffer(GL_FRAMEBUFFER, fbo);

    glBindTexture(GL_TEXTURE_CUBE_MAP, m_textureId);

    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE);

    for (GLuint i = 0; i < 6; i++) {
        glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + i, 0, GL_RGB, m_resolution, m_resolution, 0, GL_RGB, GL_UNSIGNED_BYTE, nullptr);
    }

    glFramebufferTexture(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, m_textureId, 0);

    GLenum drawBuffers[] = {GL_COLOR_ATTACHMENT0};
    glDrawBuffers(1, drawBuffers);

    Shader skyboxShader("nightsky", true);

    skyboxShader.bind();

    QMatrix4x4 projection;
    projection.perspective(90, 1, 0.01f, 100);
    QMatrix4x4 viewProjection[6];
    GLfloat matArray[6 * 16];

    viewProjection[0].lookAt(QVector3D(0,0,0), QVector3D(1,0,0), QVector3D(0, -1, 0));
    viewProjection[1].lookAt(QVector3D(0,0,0), QVector3D(-1, 0, 0), QVector3D(0, -1, 0));
    viewProjection[2].lookAt(QVector3D(0,0,0), QVector3D(0, 1, 0), QVector3D(0, 0, 1));
    viewProjection[3].lookAt(QVector3D(0,0,0), QVector3D(0, -1, 0), QVector3D(0, 0, -1));
    viewProjection[4].lookAt(QVector3D(0,0,0), QVector3D(0, 0, 1), QVector3D(0, -1, 0));
    viewProjection[5].lookAt(QVector3D(0,0,0), QVector3D(0, 0, -1), QVector3D(0, -1, 0));

    for (int i = 0; i < 6; i++) {
        viewProjection[i] = projection * viewProjection[i];
        for (int j = 0; j < 16; j++) {
            matArray[i * 16 + j] = viewProjection[i].data()[j];
        }
    }

    glUniformMatrix4fv(skyboxShader.uniformLocation("u_viewProjection"), 6, false, matArray);

    glViewport(0, 0, m_resolution, m_resolution);

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glBindVertexArray(m_vao);
        glDrawArrays(GL_TRIANGLES, 0, GLsizei(3 * 12));
    glBindVertexArray(0);
    skyboxShader.release();


    glBindFramebuffer(GL_FRAMEBUFFER, 0);
    glDeleteFramebuffers(1, &fbo);
}

void SkyBox::loadMesh()
{
    GLfloat vertices[] = {
        -1.0f, -1.0f, -1.0f,
        -1.0f, -1.0f, 1.0f,
        -1.0f, 1.0f, 1.0f,

        -1.0f, -1.0f, -1.0f,
        -1.0f, 1.0f, 1.0f,
        -1.0f, 1.0f, -1.0f,

        1.0f, -1.0f, -1.0f,
        1.0f, -1.0f, 1.0f,
        1.0f, 1.0f, 1.0f,

        1.0f, -1.0f, -1.0f,
        1.0f, 1.0f, 1.0f,
        1.0f, 1.0f, -1.0f,

        -1.0f, -1.0f, -1.0f,
        -1.0f, -1.0f, 1.0f,
        1.0f, -1.0f, 1.0f,

        -1.0f, -1.0f, -1.0f,
        1.0f, -1.0f, 1.0f,
        1.0f, -1.0f, -1.0f,

        -1.0f, 1.0f, -1.0f,
        -1.0f, 1.0f, 1.0f,
        1.0f, 1.0f, 1.0f,

        -1.0f, 1.0f, -1.0f,
        1.0f, 1.0f, 1.0f,
        1.0f, 1.0f, -1.0f,

        -1.0f, -1.0f, -1.0f,
        1.0f, 1.0f, -1.0f,
        1.0f, -1.0f, -1.0f,

        -1.0f, -1.0f, -1.0f,
        -1.0f, 1.0f, -1.0f,
        1.0f, 1.0f, -1.0f,

        -1.0f, -1.0f, 1.0f,
        1.0f, 1.0f, 1.0f,
        1.0f, -1.0f, 1.0f,

        -1.0f, -1.0f, 1.0f,
        -1.0f, 1.0f, 1.0f,
        1.0f, 1.0f, 1.0f,

    };

    glBindBuffer(GL_ARRAY_BUFFER, m_vbo);
        glBufferData(GL_ARRAY_BUFFER,
                     GLsizei(9 * 12 * sizeof(GLfloat)),
                     vertices,
                     GL_STATIC_DRAW);
    glBindBuffer(GL_ARRAY_BUFFER, 0);
}

void SkyBox::render()
{
    //glDisable(GL_DEPTH_TEST);
    m_program->setTexture("skyTexture", GL_TEXTURE0, m_textureId, GL_TEXTURE_CUBE_MAP);
    m_program->bind();
        glBindVertexArray(m_vao);
            glDrawArrays(GL_TRIANGLES, 0, GLsizei(3 * 12));
        glBindVertexArray(0);
    m_program->release();
    //glEnable(GL_DEPTH_TEST);
}