SkyBox.cpp

#include "SkyBox.h"
#include <string>
#include <vector>
#include "stb_image.h"
#include <iostream>

using namespace std;

float skyboxVertices[] = {
    // positions          
       -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
};

unsigned int skyBoxVAO, skyBoxVBO;
unsigned int skyBoxTexture;
Shader* shader;

void skyBoxInit(string imgPath) {
    getSkyBoxID(skyBoxTexture, imgPath);
    glGenVertexArrays(1, &skyBoxVAO);
    glBindVertexArray(skyBoxVAO);
    glGenBuffers(1, &skyBoxVBO);
    glBindBuffer(GL_ARRAY_BUFFER, skyBoxVBO);
    glBufferData(GL_ARRAY_BUFFER, sizeof(skyboxVertices), &skyboxVertices, GL_STATIC_DRAW);
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
}

void drawSkyBox(glm::mat4 projection, Camera camera) {
    glDepthFunc(GL_LEQUAL);
    glActiveTexture(GL_TEXTURE0);
    glBindVertexArray(skyBoxVAO);
    glBindTexture(GL_TEXTURE_CUBE_MAP, skyBoxTexture);
    glDrawArrays(GL_TRIANGLES, 0, 36);
    glDepthFunc(GL_LESS);
}

bool getSkyBoxID(unsigned int& ID, string path) {
    static vector<string> skyBoxFile{
            "/right.png",
            "/left.png",
            "/top.png",
            "/bottom.png",
            "/front.png",
            "/back.png"
    };
    glGenTextures(1, &ID);
    glBindTexture(GL_TEXTURE_CUBE_MAP, ID);
    int width, height, nrChannels;
    for (unsigned int i = 0; i < skyBoxFile.size(); i++) {
        unsigned char* data = stbi_load((path + skyBoxFile[i]).c_str(), &width, &height, &nrChannels, 0);
        if (data) {
            glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + i, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
            stbi_image_free(data);
        }
        else {
            std::cout << "Failed to open : " << skyBoxFile[i] << " (Sky box)" << std::endl;
            stbi_image_free(data);
            return false;
        }
    }
    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MAG_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);

    return true;
}