图形学笔记 -- LearnOpenGL CN 学习笔记（原书复习）

#define STB_IMAGE_IMPLEMENTATION
#include "stb_image.h"

unsigned int texture;
glGenTextures(1, &texture);
glBindTexture(GL_TEXTURE_2D, texture);
// 为当前绑定的纹理对象设置环绕、过滤方式
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
// 加载并生成纹理
int width, height, nrChannels;
unsigned char *data = stbi_load("container.jpg", &width, &height, &nrChannels, 0);
if (data)
{
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
    glGenerateMipmap(GL_TEXTURE_2D); // 多级渐远纹理 (Mipmap)
}
else
{
    std::cout << "Failed to load texture" << std::endl;
}
stbi_image_free(data);

glEnable(GL_DEPTH_TEST);
glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE); // 模板测试和深度测试都通过时 REPLACE

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);

glStencilMask(0x00); // 记得保证我们在绘制地板的时候不会更新模板缓冲
normalShader.use();
DrawFloor()

glStencilFunc(GL_ALWAYS, 1, 0xFF);
glStencilMask(0xFF); // 开启模板测试，把两个箱子写入 Stencil
DrawTwoContainers();

glStencilFunc(GL_NOTEQUAL, 1, 0xFF);
glStencilMask(0x00); // 关闭模板测试
glDisable(GL_DEPTH_TEST);
shaderSingleColor.use();
DrawTwoScaledUpContainers(); // 再次根据 Stencil 绘制箱子，GL_NOTEQUAL 1
glStencilMask(0xFF);
glEnable(GL_DEPTH_TEST);

// framebuffer configuration
// -------------------------
unsigned int framebuffer;
glGenFramebuffers(1, &framebuffer);
glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);

// create a color attachment texture
unsigned int textureColorbuffer;
glGenTextures(1, &textureColorbuffer);
glBindTexture(GL_TEXTURE_2D, textureColorbuffer);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, SCR_WIDTH, SCR_HEIGHT, 0, GL_RGB, GL_UNSIGNED_BYTE, NULL);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, textureColorbuffer, 0);

// create a renderbuffer object for depth and stencil attachment (we won't be sampling these)
unsigned int rbo;
glGenRenderbuffers(1, &rbo);
glBindRenderbuffer(GL_RENDERBUFFER, rbo);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8, SCR_WIDTH, SCR_HEIGHT); // use a single renderbuffer object for both a depth AND stencil buffer.
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_STENCIL_ATTACHMENT, GL_RENDERBUFFER, rbo); // now actually attach it

// now that we actually created the framebuffer and added all attachments we want to check if it is actually complete now
if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
    cout << "ERROR::FRAMEBUFFER:: Framebuffer is not complete!" << endl;
glBindFramebuffer(GL_FRAMEBUFFER, 0);

// render loop
// -----------
while (!glfwWindowShouldClose(window))
{
    // render
    // ------
    // bind to framebuffer and draw scene as we normally would to color texture
    glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
    glEnable(GL_DEPTH_TEST); // enable depth testing (is disabled for rendering screen-space quad)

    // make sure we clear the framebuffer's content
    glClearColor(0.1f, 0.1f, 0.1f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    shader.use();
    glm::mat4 model = glm::mat4(1.0f);
    glm::mat4 view = camera.GetViewMatrix();
    glm::mat4 projection = glm::perspective(glm::radians(camera.Zoom), (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 100.0f);
    shader.setMat4("view", view);
    shader.setMat4("projection", projection);

    // cubes
    glBindVertexArray(cubeVAO);
    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, cubeTexture);
    model = glm::translate(model, glm::vec3(-1.0f, 0.0f, -1.0f));
    shader.setMat4("model", model);
    glDrawArrays(GL_TRIANGLES, 0, 36);
    model = glm::mat4(1.0f);
    model = glm::translate(model, glm::vec3(2.0f, 0.0f, 0.0f));
    shader.setMat4("model", model);
    glDrawArrays(GL_TRIANGLES, 0, 36);

    // floor
    glBindVertexArray(planeVAO);
    glBindTexture(GL_TEXTURE_2D, floorTexture);
    shader.setMat4("model", glm::mat4(1.0f));
    glDrawArrays(GL_TRIANGLES, 0, 6);
    glBindVertexArray(0);

    // now bind back to default framebuffer and draw a quad plane with the attached framebuffer color texture
    glBindFramebuffer(GL_FRAMEBUFFER, 0);
    glDisable(GL_DEPTH_TEST); // disable depth test so screen-space quad isn't discarded due to depth test.
    // clear all relevant buffers
    glClearColor(1.0f, 1.0f, 1.0f, 1.0f); // set clear color to white (not really necessary actually, since we won't be able to see behind the quad anyways)
    glClear(GL_COLOR_BUFFER_BIT);

    screenShader.use();
    glBindVertexArray(quadVAO);
    glBindTexture(GL_TEXTURE_2D, textureColorbuffer); // use the color attachment texture as the texture of the quad plane
    glDrawArrays(GL_TRIANGLES, 0, 6);

    // glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.)
    // -------------------------------------------------------------------------------
    glfwSwapBuffers(window);
    glfwPollEvents();
}