使用open gl给立方体贴图

在 OpenGL 中，实现立方体贴图需要以下步骤：

1. 加载纹理图像并创建纹理对象。

GLuint textureID;
glGenTextures(1, &textureID);
glBindTexture(GL_TEXTURE_CUBE_MAP, textureID);
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);

int width, height, nrChannels;
unsigned char* data;
for (unsigned int i = 0; i < 6; i++)
{
    std::string filename = "texture_" + std::to_string(i) + ".png";
    data = stbi_load(filename.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 load texture" << std::endl;
        stbi_image_free(data);
    }
}

2. 创建立方体网格并绑定纹理坐标。

GLfloat vertices[] = {
    // 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
};

GLfloat texCoords[] = {
    // back face
    0.0f, 0.0f,
    0.0f, 1.0f,
    1.0f, 1.0f,
    1.0f, 1.0f,
    1.0f, 0.0f,
    0.0f, 0.0f,
    // front face
    1.0f, 0.0f,
    1.0f, 1.0f,
    0.0f, 1.0f,
    0.0f, 1.0f,
    0.0f, 0.0f,
    1.0f, 0.0f,
    // left face
    1.0f, 0.0f,
    1.0f, 1.0f,
    0.0f, 1.0f,
    0.0f, 1.0f,
    0.0f, 0.0f,
    1.0f, 0.0f,
    // right face
    0.0f, 0.0f,
    1.0f, 0.0f,
    1.0f, 1.0f,
    1.0f, 1.0f,
    0.0f, 1.0f,
    0.0f, 0.0f,
    // top face
    0.0f, 1.0f,
    0.0f, 0.0f,
    1.0f, 0.0f,
    1.0f, 0.0f,
    1.0f, 1.0f,
    0.0f, 1.0f,
    // bottom face
    1.0f, 1.0f,
    0.0f, 1.0f,
    0.0f, 0.0f,
    0.0f, 0.0f,
    1.0f, 0.0f,
    1.0f, 1.0f
};

GLuint VBO, VAO;
glGenBuffers(1, &VBO);
glGenVertexArrays(1, &VAO);

glBindVertexArray(VAO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices) + sizeof(texCoords), NULL, GL_STATIC_DRAW);
glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(vertices), vertices);
glBufferSubData(GL_ARRAY_BUFFER, sizeof(vertices), sizeof(texCoords), texCoords);

glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(GLfloat), (GLvoid*)0);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 2 * sizeof(GLfloat), (GLvoid*)sizeof(vertices));
glEnableVertexAttribArray(0);
glEnableVertexAttribArray(1);

glBindVertexArray(0);

3. 在渲染循环中使用立方体贴图。

glUseProgram(shaderProgram);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_CUBE_MAP, textureID);
glUniform1i(glGetUniformLocation(shaderProgram, "skybox"), 0);

glm::mat4 view = glm::mat4(glm::mat3(camera.GetViewMatrix()));
glm::mat4 projection = glm::perspective(glm::radians(camera.Zoom), (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 100.0f);
glUniformMatrix4fv(glGetUniformLocation(shaderProgram, "view"), 1, GL_FALSE, glm::value_ptr(view));
glUniformMatrix4fv(glGetUniformLocation(shaderProgram, "projection"), 1, GL_FALSE, glm::value_ptr(projection));

glBindVertexArray(VAO);
glDrawArrays(GL_TRIANGLES, 0, 36);
glBindVertexArray(0);

这样就可以在场景中使用立方体贴图了。