multiTexture.cpp

#include <GLFW/glfw3.h>
#include <iostream>
#include <fstream>
#include <vector>

using namespace std;

const int g_width  = 640;
const int g_height = 480;

GLuint crateShader()
{
    //バーテックスシェーダのコンパイル
    GLuint vShaderId = glCreateShader(GL_VERTEX_SHADER);
    string vertexShader = R"#(
    attribute vec3 position;
    attribute vec2 uv;
    varying vec2 vuv;
    void main(void){
        gl_Position = vec4(position, 1.0);
        vuv = uv;
    }
    )#";
    const char* vs = vertexShader.c_str();
    glShaderSource(vShaderId, 1, &vs, NULL);
    glCompileShader(vShaderId);
    
    //フラグメントシェーダのコンパイル
    GLuint fShaderId = glCreateShader(GL_FRAGMENT_SHADER);
    string fragmentShader = R"#(
    varying vec2 vuv;
    uniform sampler2D texture;
    void main(void){
        gl_FragColor = texture2D(texture, vuv);
    }
    )#";
    const char* fs = fragmentShader.c_str();
    glShaderSource(fShaderId, 1, &fs, NULL);
    glCompileShader(fShaderId);
    
    //プログラムオブジェクトの作成
    GLuint programId = glCreateProgram();
    glAttachShader(programId,vShaderId);
    glAttachShader(programId,fShaderId);
    
    // リンク
    glLinkProgram(programId);
    
    glUseProgram(programId);
    
    return programId;
}

GLuint loadTexture(string filename)
{
    // テクスチャIDの生成
    GLuint texID;
    glGenTextures(1, &texID);
    
    // ファイルの読み込み
    std::ifstream fstr(filename, std::ios::binary);
    const size_t fileSize = static_cast<size_t>(fstr.seekg(0, fstr.end).tellg());
    fstr.seekg(0, fstr.beg);
    char* textureBuffer = new char[fileSize];
    fstr.read(textureBuffer, fileSize);
    
    // テクスチャをGPUに転送
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
    glBindTexture(GL_TEXTURE_2D, texID);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 256, 256, 0, GL_RGB, GL_UNSIGNED_BYTE, textureBuffer);
    
    // テクスチャの設定
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    
    // テクスチャのアンバインド
    delete[] textureBuffer;
    glBindTexture(GL_TEXTURE_2D, 0);
    
    return texID;
}


int main()
{
    if( !glfwInit() ){
        return -1;
    }
    
    GLFWwindow* window = glfwCreateWindow(g_width, g_height, "Simple", NULL, NULL);
    if (!window)
    {
        glfwTerminate();
        return -1;
    }
    
    // モニタとの同期
    glfwMakeContextCurrent(window);
    glfwSwapInterval(1);
    
    GLuint programId = crateShader();
    
    GLuint catTexID = loadTexture("cat.raw");
    GLuint skyTexID = loadTexture("sky.raw");

    
    // ゲームループ
    while (!glfwWindowShouldClose(window)) {
        
        // 画面の初期化
        glClearColor(0.2f, 0.2f, 0.2f, 0.0f);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        glClearDepth(1.0);
        
        
        const GLfloat vertex_uv[] = {
            1, 0,
            0, 0,
            0, 1,
            1, 1,
        };
        
        // 何番目のattribute変数か
        int positionLocation = glGetAttribLocation(programId, "position");
        int uvLocation = glGetAttribLocation(programId, "uv");
        int textureLocation = glGetUniformLocation(programId, "texture");
        
        // attribute属性を有効にする
        glEnableVertexAttribArray(positionLocation);
        glEnableVertexAttribArray(uvLocation);

        // uniform属性の登録
        glUniform1i(textureLocation, 0);

        // 1枚目
        {
            // 頂点データ
            float vertex_position[] = {
                0.0f, 0.5f,
                -1.0f, 0.5f,
                -1.0f, -0.5f,
                0.0f, -0.5f
            };
            
            // attribute属性を登録
            glVertexAttribPointer(positionLocation, 2, GL_FLOAT, false, 0, vertex_position);
            glVertexAttribPointer(uvLocation, 2, GL_FLOAT, false, 0, vertex_uv);
          
            // モデルの描画
            glBindTexture(GL_TEXTURE_2D, catTexID);
            glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
        }
        
        // 2枚目
        {
            // 頂点データ
            float vertex_position[] = {
                1.0f, 0.5f,
                0.0f, 0.5f,
                0.0f, -0.5f,
                1.0f, -0.5f
            };
            
            // attribute属性を登録
            glVertexAttribPointer(positionLocation, 2, GL_FLOAT, false, 0, vertex_position);
            glVertexAttribPointer(uvLocation, 2, GL_FLOAT, false, 0, vertex_uv);
            
            // モデルの描画
            glBindTexture(GL_TEXTURE_2D, skyTexID);
            glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
        }
        
        
        // バッファの入れ替え
        glfwSwapBuffers(window);
        
        // Poll for and process events
        glfwPollEvents();
    }
    
    glfwTerminate();
    
    return 0;
}