一、为什么使用帧缓冲区对象
默认情况下,opengl 使用窗口系统提供的帧缓冲区作为绘图表面,如果应用程序只是在屏幕上绘图,则窗口系统提供的帧缓冲区通常很高效。
但是,许多应用程序需要渲染到纹理,使用默认的窗口系统不是最理想的选择
简单理解:自己接管窗口缓冲,可以干更多的事,可以做更多的特殊处理。
二、创建帧缓冲基本流程
以绘制两个箱子为例
1. API调用流程:
1.1. 创建帧缓冲对象
unsigned int fbo;
glGenFramebuffers(1, &fbo);
1.2. 激活&绑定
// bind有多重形式,可以先只考虑使用GL_FRAMEBUFFER
// 还有GL_READ_FRAMEBUFFER 、GL_DRAW_FRAMEBUFFER,
glBindFramebuffer(GL_FRAMEBUFFER, fbo);
1.3. check帧缓冲状态(没有深入理解,具体需要检测哪些数据),后面的操作渲染到当前帧缓冲中,即离屏渲染(Off-screen Rendering),窗口上看不到任何变化
if(glCheckFramebufferStatus(GL_FRAMEBUFFER) == GL_FRAMEBUFFER_COMPLETE)
1.4. 激活默认帧缓冲,绑定缓冲到0,前面的离屏渲染可以理解为在后台绘制了一张图,接下来需要把图贴回默认窗口的缓存中
glBindFramebuffer(GL_FRAMEBUFFER, 0);
// 用完了,需要删除帧缓冲对象
glDeleteFramebuffers(1, &fbo);
2. 进一步理解帧缓冲对象
注意:帧缓冲本质上是个manager,本身并没有数据,实际的数据在颜色缓冲区、深度缓冲区、模板缓冲区中,manager只是管理这些有数据的缓冲区,对这些缓冲区的引用叫“附件”,参考下图:
帧缓冲对象原理图
创建附件有两种方式:1)纹理;2)渲染缓冲对象(Renderbuffer Object)
通常的规则是,如果你不需要从一个缓冲中采样数据,那么对这个缓冲使用渲染缓冲对象会是明智的选择。如果你需要从缓冲中采样颜色或深度值等数据,那么你应该选择纹理附件。性能方面它不会产生非常大的影响的。
1)纹理附件创建,和普通的纹理差不多,区别在于,纹理的参数传递为NULL,仅分配内存,后面再进行填充
unsigned int texture;
glGenTextures(1, &texture);
glBindTexture(GL_TEXTURE_2D, texture);
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);
将纹理附加到帧缓冲上
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, texture, 0);
2)渲染缓冲对象附件
过去纹理是唯一可用的附件,渲染缓冲对象是之后引入opengl中,将数据存储为opengl原生的渲染格式,并且针对离屏渲染缓冲有优化。
API调用和其他的对象创建相似,固定的套路,创建/绑定..
unsigned int rbo;
glGenRenderbuffers(1, &rbo);
glBindRenderbuffer(GL_RENDERBUFFER, rbo);
创建一个深度和模板渲染缓冲对象
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8, 800, 600);
附加渲染缓冲对象
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_STENCIL_ATTACHMENT, GL_RENDERBUFFER, rbo);
3. 实践-基础demo实现
- 创建帧缓冲,绑定
unsigned int framebuffer;
glGenFramebuffers(1, &framebuffer);
glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
- 创建纹理,设置参数
// 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
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, texColorBuffer, 0);
- 创建一个深度和模板渲染缓冲对象
unsigned int rbo;
glGenRenderbuffers(1, &rbo);
glBindRenderbuffer(GL_RENDERBUFFER, rbo);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8, 800, 600);
glBindRenderbuffer(GL_RENDERBUFFER, 0);
- 渲染缓冲对象附加到帧缓冲的深度和模板附件上
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_STENCIL_ATTACHMENT, GL_RENDERBUFFER, rbo);
- 检查帧缓冲
if(glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
std::cout << "ERROR::FRAMEBUFFER:: Framebuffer is not complete!" << std::endl;
glBindFramebuffer(GL_FRAMEBUFFER, 0);
完整代码在文末,参考教程代码
opengl-帧缓冲代码实现
把握大的思路:切换到自定义帧缓冲-->离屏绘制-->切换到默认屏幕缓冲-->将前面的帧缓冲数据绘制到当前屏幕
这里用到了两个shader,第二个screenshader是二维的,因为自定义帧缓冲数据已经是处理好的二维数据,所以深度测试也没意义
实现效果:
帧缓冲实现简单代码 | 帧缓冲线框图 |
---|
PS:如上图,帧缓冲的线框图是两个三角形,说明离屏渲染的帧缓冲就是一个普通的纹理,贴到两个三角形上
三、实践2-后期处理
其实这部分和帧缓冲没有关系,不用帧缓冲也可以实现,放到这里讲后期处理,对帧缓冲的理解意义不大。
1. 反向,代码简单,改下片元着色器,1.0 - 当前值即可
FragColor = vec4(vec3(1.0 - texture(texture1, TexCoords)), 1.0);
原教程中修改的是窗口的shader,尝试了修改帧缓冲对应的shader也是一样的效果。有个区别是,帧缓冲处理完事一个2维的图像,再做后期处理实际的计算量就小很多,不用针对每个每个物体都做一遍,因为图形和图形之间是有重叠的。 反相
2. 灰度,rgb三通道取 (r + g + b) / 3,很好理解,根据颜色加法,rgb分量相同的叠加就是白色,除以3是尽力逼近原色彩的亮度,没有除以3也是灰白,会显得比较亮,看起来像过度曝光
灰度-正常 | 灰度-过度曝光效果 |
---|
人眼对绿色更加敏感一些,对蓝色不那么敏感,所以取权重时,调大绿色的权重,即越绿的图片,整体亮度越高。推荐下面优化的灰度算法:
void main()
{
FragColor = texture(screenTexture, TexCoords);
float average = 0.2126 * FragColor.r + 0.7152 * FragColor.g + 0.0722 * FragColor.b;
FragColor = vec4(average, average, average, 1.0);
}
此处多说两句:红绿蓝分别处于短波、中波、长波范畴,人眼对中等波长相比于其他波长更加敏感。这一现象是由进化造成,因为人类需要对身边的绿色特别敏感才能更好地在陆地上生存,这也是亮度green在图像处理中非常重要,例如压缩图像的时候,green通道的数据被完全保留,二另另个通道被大幅下采样。(下采样即压缩)
3. 核效果
3.1 锐化
教程上讲的比较简单,没有展开说
拉普拉斯算子+当前值的矩阵原理 边缘强度 + 当前值,边缘强度基于拉普拉斯(曲率-2阶微分)算子计算,这样边缘特征明显,颜色突变的点就会加重。拉普拉斯算子基于有限差分的曲率计算,包含像素周围的全部八个临近像素,成为八连通领域。参考《视觉计算基础》-第5章-特征检测-p76。
理解了原理,实现不复杂,着色器代码如下,需要注意的是,坐标范围是0-1,并不能确切的取到临近像素,所以取一个相近的值用 1.0/300.0来近似。[这点属于个人分析猜测,没有证实]
const float offset = 1.0 / 300.0;
void main()
{
vec2 offsets[9] = vec2[](
vec2(-offset, offset), // 左上
vec2( 0.0f, offset), // 正上
vec2( offset, offset), // 右上
vec2(-offset, 0.0f), // 左
vec2( 0.0f, 0.0f), // 中
vec2( offset, 0.0f), // 右
vec2(-offset, -offset), // 左下
vec2( 0.0f, -offset), // 正下
vec2( offset, -offset) // 右下
);
float kernel[9] = float[](
-1, -1, -1,
-1, 9, -1,
-1, -1, -1
);
vec3 sampleTex[9];
for(int i = 0; i < 9; i++)
{
sampleTex[i] = vec3(texture(screenTexture, TexCoords.st + offsets[i]));
}
vec3 col = vec3(0.0);
for(int i = 0; i < 9; i++)
col += sampleTex[i] * kernel[i];
FragColor = vec4(col, 1.0);
}
实现效果如下:
锐化
3.2 模糊
原理更简单,按照不同的权重取八连通领域的像素值
替换卷积核即可
模糊卷积核 模糊
3.3 边缘检测
前面讲到,锐化是基于边缘检测来实现的,边缘检测去掉当前像素值,只凸显曲率的变化即可
卷积核更新为:
边缘检测卷积核 边缘检测
五、补充
帧缓冲完整代码:
#include <glad/glad.h>
#include <GLFW/glfw3.h>
#define STB_IMAGE_IMPLEMENTATION
#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 "model.h"
#include <iostream>
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);
#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("1.colors.vs", "1.colors.fs");
Shader screenShader("5.1.framebuffers_screen.vs", "5.1.framebuffers_screen.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("resource/container.jpg");
unsigned int floorTexture = loadTexture("resource/metal.png");
// 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), (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;
}
参考:
- OpenGL ES 3.0 编程指南-十二章-帧缓冲区对象
- csdn-OpenGL之帧缓冲
- 从0开始的OpenGL学习(二十二)-帧缓存
- learnopengl-帧缓冲
- 公式编辑器 https://www.mathcha.io/editor
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