CubeMapTexture.cpp

/*
 * This file is part of Bubba-3D.
 *
 * Bubba-3D is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Bubba-3D is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with Bubba-3D. If not, see http://www.gnu.org/licenses/.
 */
#include "CubeMapTexture.h"
#include "glutil/glutil.h"
#include <Texture.h>
#include <stb_image.h>
#include <Logger.h>


CubeMapTexture::CubeMapTexture(const std::string &posXFilename, const std::string &negXFilename,
                               const std::string &posYFilename, const std::string &negYFilename,
                               const std::string &posZFilename, const std::string &negZFilename) {

    //************************************************
    //    Creating a texture ID for the OpenGL texture
    //************************************************
    GLuint textureID;
    glGenTextures(1, &textureID);

    //************************************************
    //     Load the faces into the cube map texture
    //************************************************
    glBindTexture(GL_TEXTURE_CUBE_MAP, textureID);

    loadCubeMapFace(posXFilename, GL_TEXTURE_CUBE_MAP_POSITIVE_X);
    loadCubeMapFace(negXFilename, GL_TEXTURE_CUBE_MAP_NEGATIVE_X);
    loadCubeMapFace(posYFilename, GL_TEXTURE_CUBE_MAP_POSITIVE_Y);
    loadCubeMapFace(negYFilename, GL_TEXTURE_CUBE_MAP_NEGATIVE_Y);
    loadCubeMapFace(posZFilename, GL_TEXTURE_CUBE_MAP_POSITIVE_Z);
    loadCubeMapFace(negZFilename, GL_TEXTURE_CUBE_MAP_NEGATIVE_Z);

    //************************************************
    //            Set filtering parameters
    //************************************************

    glGenerateMipmap(GL_TEXTURE_CUBE_MAP);

    // Sets the type of mipmap interpolation to be used on magnifying and 
    // minifying the active texture. 
    // For cube maps, filtering across faces causes artifacts - so disable filtering
    //glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    //glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

    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_REPEAT);
    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_R, GL_REPEAT);

    // In case you want filtering anyway, try this below instead
    //glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    //glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR); // Use tri-linear mip map filtering
    //glTexParameterf(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MAX_ANISOTROPY_EXT, 16);              // or replace trilinear mipmap filtering with nicest anisotropic filtering


    CHECK_GL_ERROR();
    m_texture = textureID;

}

CubeMapTexture::~CubeMapTexture()
{
}

void CubeMapTexture::loadCubeMapFace(std::string filename, GLenum face)
{
    // TODO(Bubbad) LET TEXTURE HANDLE ALL THIS
    stbi_set_flip_vertically_on_load(true);

    int width;
    int height;
    int comp;
    unsigned char* image = stbi_load(filename.c_str(), &width, &height, &comp, 0);

    if (image == nullptr) {
        Logger::logError("Couldnt load image "+ filename);
    }

    GLenum format = comp == 3 ? GL_RGB : GL_RGBA;

    glTexImage2D(face, 0, GL_SRGB_ALPHA_EXT, width, height, 0, format, GL_UNSIGNED_BYTE, image);

    stbi_image_free(image);
}

void CubeMapTexture::bind(GLenum textureUnit) {
    glActiveTexture(textureUnit);
//    glEnable(GL_TEXTURE_2D);
    glBindTexture(GL_TEXTURE_CUBE_MAP, m_texture);
}