OpenGL学习笔记十六（帧缓存）
帧缓存的概念
到目前位置，已经介绍了多种缓存（数据），
- 用于写入颜色值的颜色缓冲
- 用于写入深度信息的深度缓冲
- 允许我们根据一些条件丢弃特定片段的模板缓冲
这些缓冲结合起来叫做帧缓冲(Framebuffer)
帧缓存的作用
- 用于保存渲染结果数据
- 用于实现自定义后效，可实现非常炫酷的后效
自定义帧缓存
创建对象：
unsigned int fbo;
//初始化值
glGenFramebuffers(1, &fbo);
//将fbo绑定到GL_FRAMEBUFFER上，所有的读取和写入帧缓冲的操作将会影响当前绑定的帧缓冲
glBindFramebuffer(GL_FRAMEBUFFER, fbo);
glBindFramebuffer可选参数：
- GL_READ_FRAMEBUFFER：
将一个帧缓冲绑定到读取目标，绑定到GL_READ_FRAMEBUFFER的帧缓冲将会使用在所有像是glReadPixels的读取操作中 - GL_DRAW_FRAMEBUFFER：
将一个帧缓冲绑定到写入目标，绑定到GL_DRAW_FRAMEBUFFER的帧缓冲将会被用作渲染、清除等写入操作的目标
大部分情况你都不需要区分它们，通常都会使用GL_FRAMEBUFFER，绑定到两个上。
还不能使用我们的帧缓冲，因为它还不完整，检测函数
一个完整的帧缓冲需要满足以下的条件：
- 附加至少一个缓冲（颜色、深度或模板缓冲）。
- 至少有一个颜色附件(Attachment)。
- 所有的附件都必须是完整的（保留了内存）。
- 每个缓冲都应该有相同的样本数。
检测完整性的函数：
glCheckFramebufferStatus(GL_FRAMEBUFFER) == GL_FRAMEBUFFER_COMPLETE
删除帧缓冲对象
glDeleteFramebuffers(1, &fbo);
为帧缓冲分配空间
分配空间的方式有两种：纹理或渲染缓冲对象(Renderbuffer Object)。
- 纹理
将帧缓冲中的内容保存至一张纹理贴图中，方便读写，可以传入shader中做后期处理。 - 渲染缓冲对象
将帧缓冲中的数据放在渲染缓冲对象中，因为该对象是原始数据，渲染缓冲对象是一个真正的缓冲，即一系列的字节、整数、像素等。渲染缓冲对象附加的好处是，它会将数据储存为OpenGL原生的渲染格式，可以快速进行数组传值，缺点是只写的，不可读取，适合处理深度缓存和模板缓存。
渲染到纹理：
- 创建纹理，使用图形库stb_image.h
- 将纹理附加到帧缓冲
unsigned int framebuffer;
glGenFramebuffers(1, &framebuffer);
glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
// 生成纹理
unsigned int texColorBuffer;
glGenTextures(1, &texColorBuffer);
glBindTexture(GL_TEXTURE_2D, texColorBuffer);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 800, 600, 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);
glBindTexture(GL_TEXTURE_2D, 0);
// 将它附加到当前绑定的帧缓冲对象，颜色缓存
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, texColorBuffer, 0);
glFrameBufferTexture2D有以下的参数：
- target：帧缓冲的目标（绘制、读取或者两者皆有）
- attachment：我们想要附加的附件类型。当前我们正在附加一个颜色附件。注意最后的0意味着我们可以附加多个颜色附件。我们将在之后的教程中提到。
- textarget：你希望附加的纹理类型
- texture：要附加的纹理本身
- level：多级渐远纹理的级别。我们将它保留为0。
渲染到Renderbuffer Object：
- 创建Renderbuffer Object
- 分配空间
unsigned int rbo;
glGenRenderbuffers(1, &rbo);
glBindRenderbuffer(GL_RENDERBUFFER, rbo);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8, 800, 600);
glBindRenderbuffer(GL_RENDERBUFFER, 0);
//深度和模板缓存
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_STENCIL_ATTACHMENT, GL_RENDERBUFFER, rbo);
实战实例
shader.h内容
#pragma once
#ifndef SHADER_H
#define SHADER_H
#include <glad/glad.h>
#include <glm/glm.hpp>
#include <string>
#include <fstream>
#include <sstream>
#include <iostream>
class Shader
{
public:
unsigned int ID;
// constructor generates the shader on the fly
// ------------------------------------------------------------------------
Shader(const char* vertexPath, const char* fragmentPath, const char* geometryPath = nullptr)
{
// 1. retrieve the vertex/fragment source code from filePath
std::string vertexCode;
std::string fragmentCode;
std::string geometryCode;
std::ifstream vShaderFile;
std::ifstream fShaderFile;
std::ifstream gShaderFile;
// ensure ifstream objects can throw exceptions:
vShaderFile.exceptions(std::ifstream::failbit | std::ifstream::badbit);
fShaderFile.exceptions(std::ifstream::failbit | std::ifstream::badbit);
gShaderFile.exceptions(std::ifstream::failbit | std::ifstream::badbit);
try
{
// open files
vShaderFile.open(vertexPath);
fShaderFile.open(fragmentPath);
std::stringstream vShaderStream, fShaderStream;
// read file's buffer contents into streams
vShaderStream << vShaderFile.rdbuf();
fShaderStream << fShaderFile.rdbuf();
// close file handlers
vShaderFile.close();
fShaderFile.close();
// convert stream into string
vertexCode = vShaderStream.str();
fragmentCode = fShaderStream.str();
// if geometry shader path is present, also load a geometry shader
if (geometryPath != nullptr)
{
gShaderFile.open(geometryPath);
std::stringstream gShaderStream;
gShaderStream << gShaderFile.rdbuf();
gShaderFile.close();
geometryCode = gShaderStream.str();
}
}
catch (std::ifstream::failure e)
{
std::cout << "ERROR::SHADER::FILE_NOT_SUCCESFULLY_READ" << std::endl;
}
const char* vShaderCode = vertexCode.c_str();
const char * fShaderCode = fragmentCode.c_str();
// 2. compile shaders
unsigned int vertex, fragment;
// vertex shader
vertex = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertex, 1, &vShaderCode, NULL);
glCompileShader(vertex);
checkCompileErrors(vertex, "VERTEX");
// fragment Shader
fragment = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragment, 1, &fShaderCode, NULL);
glCompileShader(fragment);
checkCompileErrors(fragment, "FRAGMENT");
// if geometry shader is given, compile geometry shader
unsigned int geometry;
if (geometryPath != nullptr)
{
const char * gShaderCode = geometryCode.c_str();
geometry = glCreateShader(GL_GEOMETRY_SHADER);
glShaderSource(geometry, 1, &gShaderCode, NULL);
glCompileShader(geometry);
checkCompileErrors(geometry, "GEOMETRY");
}
// shader Program
ID = glCreateProgram();
glAttachShader(ID, vertex);
glAttachShader(ID, fragment);
if (geometryPath != nullptr)
glAttachShader(ID, geometry);
glLinkProgram(ID);
checkCompileErrors(ID, "PROGRAM");
// delete the shaders as they're linked into our program now and no longer necessery
glDeleteShader(vertex);
glDeleteShader(fragment);
if (geometryPath != nullptr)
glDeleteShader(geometry);
}
// activate the shader
// ------------------------------------------------------------------------
void use()
{
glUseProgram(ID);
}
// utility uniform functions
// ------------------------------------------------------------------------
void setBool(const std::string &name, bool value) const
{
glUniform1i(glGetUniformLocation(ID, name.c_str()), (int)value);
}
// ------------------------------------------------------------------------
void setInt(const std::string &name, int value) const
{
glUniform1i(glGetUniformLocation(ID, name.c_str()), value);
}
// ------------------------------------------------------------------------
void setFloat(const std::string &name, float value) const
{
glUniform1f(glGetUniformLocation(ID, name.c_str()), value);
}
// ------------------------------------------------------------------------
void setVec2(const std::string &name, const glm::vec2 &value) const
{
glUniform2fv(glGetUniformLocation(ID, name.c_str()), 1, &value[0]);
}
void setVec2(const std::string &name, float x, float y) const
{
glUniform2f(glGetUniformLocation(ID, name.c_str()), x, y);
}
// ------------------------------------------------------------------------
void setVec3(const std::string &name, const glm::vec3 &value) const
{
glUniform3fv(glGetUniformLocation(ID, name.c_str()), 1, &value[0]);
}
void setVec3(const std::string &name, float x, float y, float z) const
{
glUniform3f(glGetUniformLocation(ID, name.c_str()), x, y, z);
}
// ------------------------------------------------------------------------
void setVec4(const std::string &name, const glm::vec4 &value) const
{
glUniform4fv(glGetUniformLocation(ID, name.c_str()), 1, &value[0]);
}
void setVec4(const std::string &name, float x, float y, float z, float w)
{
glUniform4f(glGetUniformLocation(ID, name.c_str()), x, y, z, w);
}
// ------------------------------------------------------------------------
void setMat2(const std::string &name, const glm::mat2 &mat) const
{
glUniformMatrix2fv(glGetUniformLocation(ID, name.c_str()), 1, GL_FALSE, &mat[0][0]);
}
// ------------------------------------------------------------------------
void setMat3(const std::string &name, const glm::mat3 &mat) const
{
glUniformMatrix3fv(glGetUniformLocation(ID, name.c_str()), 1, GL_FALSE, &mat[0][0]);
}
// ------------------------------------------------------------------------
void setMat4(const std::string &name, const glm::mat4 &mat) const
{
glUniformMatrix4fv(glGetUniformLocation(ID, name.c_str()), 1, GL_FALSE, &mat[0][0]);
}
private:
// utility function for checking shader compilation/linking errors.
// ------------------------------------------------------------------------
void checkCompileErrors(GLuint shader, std::string type)
{
GLint success;
GLchar infoLog[1024];
if (type != "PROGRAM")
{
glGetShaderiv(shader, GL_COMPILE_STATUS, &success);
if (!success)
{
glGetShaderInfoLog(shader, 1024, NULL, infoLog);
std::cout << "ERROR::SHADER_COMPILATION_ERROR of type: " << type << "\n" << infoLog << "\n -- --------------------------------------------------- -- " << std::endl;
}
}
else
{
glGetProgramiv(shader, GL_LINK_STATUS, &success);
if (!success)
{
glGetProgramInfoLog(shader, 1024, NULL, infoLog);
std::cout << "ERROR::PROGRAM_LINKING_ERROR of type: " << type << "\n" << infoLog << "\n -- --------------------------------------------------- -- " << std::endl;
}
}
}
};
#endif
camera.h内容
#pragma once
#ifndef CAMERA_H
#define CAMERA_H
#include <glad/glad.h>
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <vector>
// Defines several possible options for camera movement. Used as abstraction to stay away from window-system specific input methods
enum Camera_Movement {
FORWARD,
BACKWARD,
LEFT,
RIGHT
};
// Default camera values
const float YAW = -90.0f;
const float PITCH = 0.0f;
const float SPEED = 2.5f;
const float SENSITIVITY = 0.1f;
const float ZOOM = 45.0f;
// An abstract camera class that processes input and calculates the corresponding Euler Angles, Vectors and Matrices for use in OpenGL
class Camera
{
public:
// Camera Attributes
glm::vec3 Position;
glm::vec3 Front;
glm::vec3 Up;
glm::vec3 Right;
glm::vec3 WorldUp;
// Euler Angles
float Yaw;
float Pitch;
// Camera options
float MovementSpeed;
float MouseSensitivity;
float Zoom;
// Constructor with vectors
Camera(glm::vec3 position = glm::vec3(0.0f, 0.0f, 0.0f), glm::vec3 up = glm::vec3(0.0f, 1.0f, 0.0f), float yaw = YAW, float pitch = PITCH) : Front(glm::vec3(0.0f, 0.0f, -1.0f)), MovementSpeed(SPEED), MouseSensitivity(SENSITIVITY), Zoom(ZOOM)
{
Position = position;
WorldUp = up;
Yaw = yaw;
Pitch = pitch;
updateCameraVectors();
}
// Constructor with scalar values
Camera(float posX, float posY, float posZ, float upX, float upY, float upZ, float yaw, float pitch) : Front(glm::vec3(0.0f, 0.0f, -1.0f)), MovementSpeed(SPEED), MouseSensitivity(SENSITIVITY), Zoom(ZOOM)
{
Position = glm::vec3(posX, posY, posZ);
WorldUp = glm::vec3(upX, upY, upZ);
Yaw = yaw;
Pitch = pitch;
updateCameraVectors();
}
// Returns the view matrix calculated using Euler Angles and the LookAt Matrix
glm::mat4 GetViewMatrix()
{
return glm::lookAt(Position, Position + Front, Up);
}
// Processes input received from any keyboard-like input system. Accepts input parameter in the form of camera defined ENUM (to abstract it from windowing systems)
void ProcessKeyboard(Camera_Movement direction, float deltaTime)
{
float velocity = MovementSpeed * deltaTime;
if (direction == FORWARD)
Position += Front * velocity;
if (direction == BACKWARD)
Position -= Front * velocity;
if (direction == LEFT)
Position -= Right * velocity;
if (direction == RIGHT)
Position += Right * velocity;
}
// Processes input received from a mouse input system. Expects the offset value in both the x and y direction.
void ProcessMouseMovement(float xoffset, float yoffset, GLboolean constrainPitch = true)
{
xoffset *= MouseSensitivity;
yoffset *= MouseSensitivity;
Yaw += xoffset;
Pitch += yoffset;
// Make sure that when pitch is out of bounds, screen doesn't get flipped
if (constrainPitch)
{
if (Pitch > 89.0f)
Pitch = 89.0f;
if (Pitch < -89.0f)
Pitch = -89.0f;
}
// Update Front, Right and Up Vectors using the updated Euler angles
updateCameraVectors();
}
// Processes input received from a mouse scroll-wheel event. Only requires input on the vertical wheel-axis
void ProcessMouseScroll(float yoffset)
{
if (Zoom >= 1.0f && Zoom <= 45.0f)
Zoom -= yoffset;
if (Zoom <= 1.0f)
Zoom = 1.0f;
if (Zoom >= 45.0f)
Zoom = 45.0f;
}
private:
// Calculates the front vector from the Camera's (updated) Euler Angles
void updateCameraVectors()
{
// Calculate the new Front vector
glm::vec3 front;
front.x = cos(glm::radians(Yaw)) * cos(glm::radians(Pitch));
front.y = sin(glm::radians(Pitch));
front.z = sin(glm::radians(Yaw)) * cos(glm::radians(Pitch));
Front = glm::normalize(front);
// Also re-calculate the Right and Up vector
Right = glm::normalize(glm::cross(Front, WorldUp)); // Normalize the vectors, because their length gets closer to 0 the more you look up or down which results in slower movement.
Up = glm::normalize(glm::cross(Right, Front));
}
};
#endif
测试程序：绘制与实际效果相反的颜色
#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include "stb_image.h"
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>
#include "shader.h"
#include "camera.h"
#include <iostream>
using namespace std;
void framebuffer_size_callback(GLFWwindow* window, int width, int height);
void mouse_callback(GLFWwindow* window, double xpos, double ypos);
void scroll_callback(GLFWwindow* window, double xoffset, double yoffset);
void processInput(GLFWwindow *window);
unsigned int loadTexture(const char *path);
// settings
const unsigned int SCR_WIDTH = 800;
const unsigned int SCR_HEIGHT = 600;
// camera
Camera camera(glm::vec3(0.0f, 0.0f, 3.0f));
float lastX = (float)SCR_WIDTH / 2.0;
float lastY = (float)SCR_HEIGHT / 2.0;
bool firstMouse = true;
// timing
float deltaTime = 0.0f;
float lastFrame = 0.0f;
int main()
{
// glfw: initialize and configure
// ------------------------------
glfwInit();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
#ifdef __APPLE__
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); // uncomment this statement to fix compilation on OS X
#endif
// glfw window creation
// --------------------
GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL);
if (window == NULL)
{
std::cout << "Failed to create GLFW window" << std::endl;
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);
glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
glfwSetCursorPosCallback(window, mouse_callback);
glfwSetScrollCallback(window, scroll_callback);
// tell GLFW to capture our mouse
glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);
// glad: load all OpenGL function pointers
// ---------------------------------------
if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
{
std::cout << "Failed to initialize GLAD" << std::endl;
return -1;
}
// configure global opengl state
// -----------------------------
glEnable(GL_DEPTH_TEST);
// build and compile shaders
// -------------------------
Shader shader("framebuffer.vs", "framebuffer.fs");
Shader screenShader("framebuffer_scene.vs", "framebuffer_scene.fs");
// set up vertex data (and buffer(s)) and configure vertex attributes
// ------------------------------------------------------------------
float cubeVertices[] = {
// positions // texture Coords
-0.5f, -0.5f, -0.5f, 0.0f, 0.0f,
0.5f, -0.5f, -0.5f, 1.0f, 0.0f,
0.5f, 0.5f, -0.5f, 1.0f, 1.0f,
0.5f, 0.5f, -0.5f, 1.0f, 1.0f,
-0.5f, 0.5f, -0.5f, 0.0f, 1.0f,
-0.5f, -0.5f, -0.5f, 0.0f, 0.0f,
-0.5f, -0.5f, 0.5f, 0.0f, 0.0f,
0.5f, -0.5f, 0.5f, 1.0f, 0.0f,
0.5f, 0.5f, 0.5f, 1.0f, 1.0f,
0.5f, 0.5f, 0.5f, 1.0f, 1.0f,
-0.5f, 0.5f, 0.5f, 0.0f, 1.0f,
-0.5f, -0.5f, 0.5f, 0.0f, 0.0f,
-0.5f, 0.5f, 0.5f, 1.0f, 0.0f,
-0.5f, 0.5f, -0.5f, 1.0f, 1.0f,
-0.5f, -0.5f, -0.5f, 0.0f, 1.0f,
-0.5f, -0.5f, -0.5f, 0.0f, 1.0f,
-0.5f, -0.5f, 0.5f, 0.0f, 0.0f,
-0.5f, 0.5f, 0.5f, 1.0f, 0.0f,
0.5f, 0.5f, 0.5f, 1.0f, 0.0f,
0.5f, 0.5f, -0.5f, 1.0f, 1.0f,
0.5f, -0.5f, -0.5f, 0.0f, 1.0f,
0.5f, -0.5f, -0.5f, 0.0f, 1.0f,
0.5f, -0.5f, 0.5f, 0.0f, 0.0f,
0.5f, 0.5f, 0.5f, 1.0f, 0.0f,
-0.5f, -0.5f, -0.5f, 0.0f, 1.0f,
0.5f, -0.5f, -0.5f, 1.0f, 1.0f,
0.5f, -0.5f, 0.5f, 1.0f, 0.0f,
0.5f, -0.5f, 0.5f, 1.0f, 0.0f,
-0.5f, -0.5f, 0.5f, 0.0f, 0.0f,
-0.5f, -0.5f, -0.5f, 0.0f, 1.0f,
-0.5f, 0.5f, -0.5f, 0.0f, 1.0f,
0.5f, 0.5f, -0.5f, 1.0f, 1.0f,
0.5f, 0.5f, 0.5f, 1.0f, 0.0f,
0.5f, 0.5f, 0.5f, 1.0f, 0.0f,
-0.5f, 0.5f, 0.5f, 0.0f, 0.0f,
-0.5f, 0.5f, -0.5f, 0.0f, 1.0f
};
float planeVertices[] = {
// positions // texture Coords
5.0f, -0.5f, 5.0f, 2.0f, 0.0f,
-5.0f, -0.5f, 5.0f, 0.0f, 0.0f,
-5.0f, -0.5f, -5.0f, 0.0f, 2.0f,
5.0f, -0.5f, 5.0f, 2.0f, 0.0f,
-5.0f, -0.5f, -5.0f, 0.0f, 2.0f,
5.0f, -0.5f, -5.0f, 2.0f, 2.0f
};
float quadVertices[] = { // vertex attributes for a quad that fills the entire screen in Normalized Device Coordinates.
// positions // texCoords
-1.0f, 1.0f, 0.0f, 1.0f,
-1.0f, -1.0f, 0.0f, 0.0f,
1.0f, -1.0f, 1.0f, 0.0f,
-1.0f, 1.0f, 0.0f, 1.0f,
1.0f, -1.0f, 1.0f, 0.0f,
1.0f, 1.0f, 1.0f, 1.0f
};
// cube VAO
unsigned int cubeVAO, cubeVBO;
glGenVertexArrays(1, &cubeVAO);
glGenBuffers(1, &cubeVBO);
glBindVertexArray(cubeVAO);
glBindBuffer(GL_ARRAY_BUFFER, cubeVBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(cubeVertices), &cubeVertices, GL_STATIC_DRAW);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)0);
glEnableVertexAttribArray(1);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)(3 * sizeof(float)));
// plane VAO
unsigned int planeVAO, planeVBO;
glGenVertexArrays(1, &planeVAO);
glGenBuffers(1, &planeVBO);
glBindVertexArray(planeVAO);
glBindBuffer(GL_ARRAY_BUFFER, planeVBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(planeVertices), &planeVertices, GL_STATIC_DRAW);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)0);
glEnableVertexAttribArray(1);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)(3 * sizeof(float)));
// screen quad VAO
unsigned int quadVAO, quadVBO;
glGenVertexArrays(1, &quadVAO);
glGenBuffers(1, &quadVBO);
glBindVertexArray(quadVAO);
glBindBuffer(GL_ARRAY_BUFFER, quadVBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(quadVertices), &quadVertices, GL_STATIC_DRAW);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(float), (void*)0);
glEnableVertexAttribArray(1);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(float), (void*)(2 * sizeof(float)));
// load textures
// -------------
unsigned int cubeTexture = loadTexture("1.jpg");
unsigned int floorTexture = loadTexture("2.jpg");
// shader configuration
// --------------------
shader.use();
shader.setInt("texture1", 0);
screenShader.use();
screenShader.setInt("screenTexture", 0);
// 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);
// draw as wireframe
//glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
// render loop
// -----------
while (!glfwWindowShouldClose(window))
{
// per-frame time logic
// --------------------
float currentFrame = glfwGetTime();
deltaTime = currentFrame - lastFrame;
lastFrame = currentFrame;
// input
// -----
processInput(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*200), (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 necessery 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();
}
// optional: de-allocate all resources once they've outlived their purpose:
// ------------------------------------------------------------------------
glDeleteVertexArrays(1, &cubeVAO);
glDeleteVertexArrays(1, &planeVAO);
glDeleteVertexArrays(1, &quadVAO);
glDeleteBuffers(1, &cubeVBO);
glDeleteBuffers(1, &planeVBO);
glDeleteBuffers(1, &quadVBO);
glfwTerminate();
return 0;
}
// process all input: query GLFW whether relevant keys are pressed/released this frame and react accordingly
// ---------------------------------------------------------------------------------------------------------
void processInput(GLFWwindow *window)
{
if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
glfwSetWindowShouldClose(window, true);
if (glfwGetKey(window, GLFW_KEY_W) == GLFW_PRESS)
camera.ProcessKeyboard(FORWARD, deltaTime);
if (glfwGetKey(window, GLFW_KEY_S) == GLFW_PRESS)
camera.ProcessKeyboard(BACKWARD, deltaTime);
if (glfwGetKey(window, GLFW_KEY_A) == GLFW_PRESS)
camera.ProcessKeyboard(LEFT, deltaTime);
if (glfwGetKey(window, GLFW_KEY_D) == GLFW_PRESS)
camera.ProcessKeyboard(RIGHT, deltaTime);
}
// glfw: whenever the window size changed (by OS or user resize) this callback function executes
// ---------------------------------------------------------------------------------------------
void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
// make sure the viewport matches the new window dimensions; note that width and
// height will be significantly larger than specified on retina displays.
glViewport(0, 0, width, height);
}
// glfw: whenever the mouse moves, this callback is called
// -------------------------------------------------------
void mouse_callback(GLFWwindow* window, double xpos, double ypos)
{
if (firstMouse)
{
lastX = xpos;
lastY = ypos;
firstMouse = false;
}
float xoffset = xpos - lastX;
float yoffset = lastY - ypos; // reversed since y-coordinates go from bottom to top
lastX = xpos;
lastY = ypos;
camera.ProcessMouseMovement(xoffset, yoffset);
}
// glfw: whenever the mouse scroll wheel scrolls, this callback is called
// ----------------------------------------------------------------------
void scroll_callback(GLFWwindow* window, double xoffset, double yoffset)
{
camera.ProcessMouseScroll(yoffset);
}
// utility function for loading a 2D texture from file
// ---------------------------------------------------
unsigned int loadTexture(char const * path)
{
unsigned int textureID;
glGenTextures(1, &textureID);
int width, height, nrComponents;
unsigned char *data = stbi_load(path, &width, &height, &nrComponents, 0);
if (data)
{
GLenum format;
if (nrComponents == 1)
format = GL_RED;
else if (nrComponents == 3)
format = GL_RGB;
else if (nrComponents == 4)
format = GL_RGBA;
glBindTexture(GL_TEXTURE_2D, textureID);
glTexImage2D(GL_TEXTURE_2D, 0, format, width, height, 0, format, GL_UNSIGNED_BYTE, data);
glGenerateMipmap(GL_TEXTURE_2D);
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_MIPMAP_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
stbi_image_free(data);
}
else
{
std::cout << "Texture failed to load at path: " << path << std::endl;
stbi_image_free(data);
}
return textureID;
}
framebuffer.fs
#version 330 core
out vec4 FragColor;
in vec2 TexCoords;
uniform sampler2D texture1;
void main()
{
FragColor = texture(texture1, TexCoords);
}
framebuffer.vs
#version 330 core
layout (location = 0) in vec3 aPos;
layout (location = 1) in vec2 aTexCoords;
out vec2 TexCoords;
uniform mat4 model;
uniform mat4 view;
uniform mat4 projection;
void main()
{
TexCoords = aTexCoords;
gl_Position = projection * view * model * vec4(aPos, 1.0);
}
framebuffer_scene.fs
#version 330 core
out vec4 FragColor;
in vec2 TexCoords;
uniform sampler2D screenTexture;
void main()
{
vec3 col = 1-texture(screenTexture, TexCoords).rgb;
FragColor = vec4(col, 1.0);
}
framebuffer_scene.vs
#version 330 core
layout (location = 0) in vec2 aPos;
layout (location = 1) in vec2 aTexCoords;
out vec2 TexCoords;
void main()
{
TexCoords = aTexCoords;
gl_Position = vec4(aPos.x, aPos.y, 0.0, 1.0);
}
使用的图片
](https://img-blog.csdnimg.cn/20200328183016767.jpg?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM2Njk2NDg2,size_16,color_FFFFFF,t_70)
其他头文件引入请参考
OpenGL学习笔记四——使用stb_image.h加载纹理，理解Mipmap，实现纹理映射
OpenGL学习笔记三——引入GLM库，实现transform
OpenGL 开发环境配置（Windows） - Visual Studio 2017 + GLFW + GLAD 详细教程
