分别将画面渲染到屏幕的左上，坐下，右上，右下区域效果图：

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【opengl将画面渲染到屏幕的指定区域和多屏渲染】
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多屏渲染效果图：

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原理见代码注释

#include "FullScreenQuad.h"void FullScreenQuad::Init() { glGenBuffers(1, &mVBO); glBindBuffer(GL_ARRAY_BUFFER, mVBO); glBufferData(GL_ARRAY_BUFFER, sizeof(float) * 20, nullptr, GL_STATIC_DRAW); glBindBuffer(GL_ARRAY_BUFFER, 0); }//绘制一个铺满屏幕的四边形 void FullScreenQuad::Draw(GLint posLoc, GLint texcoordLoc) { //draw fullscreen float vertices[] = { -0.5f,-0.5f,-1.0f,0.0f,0.0f, 0.5f,-0.5f,-1.0f,1.0f,0.0f, 0.5f,0.5f,-1.0f,1.0f,1.0f, -0.5f,0.5f,-1.0f,0.0f,1.0f }; glBindBuffer(GL_ARRAY_BUFFER, mVBO); //绑定到vbo glBufferData(GL_ARRAY_BUFFER, sizeof(float) * 20, vertices, GL_STATIC_DRAW); //顶点数据上传至显卡 glBindBuffer(GL_ARRAY_BUFFER, 0); glBindBuffer(GL_ARRAY_BUFFER, mVBO); glEnableVertexAttribArray(posLoc); //启用顶点坐标属性 //指定顶点数据在VBO中的入口地址 glVertexAttribPointer(posLoc, 3, GL_FLOAT, GL_FALSE, sizeof(float) * 5, 0); glEnableVertexAttribArray(texcoordLoc); //启用顶点纹理坐标属性 //指定顶点纹理坐标在VBO中的入口地址 glVertexAttribPointer(texcoordLoc, 2, GL_FLOAT, GL_FALSE, sizeof(float) * 5, (void*)(sizeof(float)*3)); glDrawArrays(GL_QUADS, 0, 4); glBindBuffer(GL_ARRAY_BUFFER, 0); }//绘制左上角四分之一的矩形 void FullScreenQuad::DrawToLeftTop(GLint posLoc, GLint texcoordLoc) { float vertices[] = { -0.5f,0.0f,-1.0f,0.0f,0.0f, 0.0f,0.0f,-1.0f,1.0f,0.0f, 0.0f,0.5f,-1.0f,1.0f,1.0f, -0.5f,0.5f,-1.0f,0.0f,1.0f }; glBindBuffer(GL_ARRAY_BUFFER, mVBO); glBufferData(GL_ARRAY_BUFFER, sizeof(float) * 20, vertices, GL_STATIC_DRAW); glBindBuffer(GL_ARRAY_BUFFER, 0); glBindBuffer(GL_ARRAY_BUFFER, mVBO); glEnableVertexAttribArray(posLoc); glVertexAttribPointer(posLoc, 3, GL_FLOAT, GL_FALSE, sizeof(float) * 5, 0); glEnableVertexAttribArray(texcoordLoc); glVertexAttribPointer(texcoordLoc, 2, GL_FLOAT, GL_FALSE, sizeof(float) * 5, (void*)(sizeof(float) * 3)); glDrawArrays(GL_QUADS, 0, 4); glBindBuffer(GL_ARRAY_BUFFER, 0); }//绘制左下角四分之的矩形 void FullScreenQuad::DrawToLeftBottom(GLint posLoc, GLint texcoordLoc) { float vertices[] = { -0.5f,-0.5f,-1.0f,0.0f,0.0f, 0.0f,-0.5f,-1.0f,1.0f,0.0f, 0.0f,0.0f,-1.0f,1.0f,1.0f, -0.5f,0.0f,-1.0f,0.0f,1.0f }; glBindBuffer(GL_ARRAY_BUFFER, mVBO); glBufferData(GL_ARRAY_BUFFER, sizeof(float) * 20, vertices, GL_STATIC_DRAW); glBindBuffer(GL_ARRAY_BUFFER, 0); glBindBuffer(GL_ARRAY_BUFFER, mVBO); glEnableVertexAttribArray(posLoc); glVertexAttribPointer(posLoc, 3, GL_FLOAT, GL_FALSE, sizeof(float) * 5, 0); glEnableVertexAttribArray(texcoordLoc); glVertexAttribPointer(texcoordLoc, 2, GL_FLOAT, GL_FALSE, sizeof(float) * 5, (void*)(sizeof(float) * 3)); glDrawArrays(GL_QUADS, 0, 4); glBindBuffer(GL_ARRAY_BUFFER, 0); }//绘制右上角四分之一的矩形 void FullScreenQuad::DrawToRightTop(GLint posLoc, GLint texcoordLoc) { float vertices[] = { 0.0f,-0.0f,-1.0f,0.0f,0.0f, 0.5f,-0.0f,-1.0f,1.0f,0.0f, 0.5f,0.5f,-1.0f,1.0f,1.0f, 0.0f,0.5f,-1.0f,0.0f,1.0f }; glBindBuffer(GL_ARRAY_BUFFER, mVBO); glBufferData(GL_ARRAY_BUFFER, sizeof(float) * 20, vertices, GL_STATIC_DRAW); glBindBuffer(GL_ARRAY_BUFFER, 0); glBindBuffer(GL_ARRAY_BUFFER, mVBO); glEnableVertexAttribArray(posLoc); glVertexAttribPointer(posLoc, 3, GL_FLOAT, GL_FALSE, sizeof(float) * 5, 0); glEnableVertexAttribArray(texcoordLoc); glVertexAttribPointer(texcoordLoc, 2, GL_FLOAT, GL_FALSE, sizeof(float) * 5, (void*)(sizeof(float) * 3)); glDrawArrays(GL_QUADS, 0, 4); glBindBuffer(GL_ARRAY_BUFFER, 0); }//绘制右下角四分之的矩形 void FullScreenQuad::DrawToRightBottom(GLint posLoc, GLint texcoordLoc) { float vertices[] = { 0.0f,-0.5f,-1.0f,0.0f,0.0f, 0.5f,-0.5f,-1.0f,1.0f,0.0f, 0.5f,0.0f,-1.0f,1.0f,1.0f, 0.0f,0.0f,-1.0f,0.0f,1.0f }; glBindBuffer(GL_ARRAY_BUFFER, mVBO); glBufferData(GL_ARRAY_BUFFER, sizeof(float) * 20, vertices, GL_STATIC_DRAW); glBindBuffer(GL_ARRAY_BUFFER, 0); glBindBuffer(GL_ARRAY_BUFFER, mVBO); glEnableVertexAttribArray(posLoc); glVertexAttribPointer(posLoc, 3, GL_FLOAT, GL_FALSE, sizeof(float) * 5, 0); glEnableVertexAttribArray(texcoordLoc); glVertexAttribPointer(texcoordLoc, 2, GL_FLOAT, GL_FALSE, sizeof(float) * 5, (void*)(sizeof(float) * 3)); glDrawArrays(GL_QUADS, 0, 4); glBindBuffer(GL_ARRAY_BUFFER, 0); }

渲染入口
渲染步骤
一，使用带光照效果的shader
1,首先创建一个fbo
2,在此fbo中绘制三个带光照效果的立方体(每个立方体都有各自的模型矩阵和法线矩阵)
3,分别设置三个立方体的光源并绘制
二，切换shader，使用绘制四边形的shader
4,分别在屏幕的左上，左下，右上，右下绘制四个四边形
5,将此前绘制在fbo中的内容作为纹理贴在绘制的四个四边形中

#include #include "glew.h" #include #include #include "utils.h" #include "GPUProgram.h" #include "ObjModel.h" #include "FBO.h" #include "FullScreenQuad.h" #include "Glm/glm.hpp" #include "Glm/ext.hpp" #pragma comment(lib,"opengl32.lib") #pragma comment(lib,"glew32.lib")LRESULT CALLBACK GLWindowProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) { switch (msg) { case WM_CLOSE: PostQuitMessage(0); break; } return DefWindowProc(hwnd,msg,wParam,lParam); }INT WINAPI WinMain(_In_ HINSTANCE hInstance, _In_opt_ HINSTANCE hPrevInstance, _In_ LPSTR lpCmdLine, _In_ int nShowCmd) { WNDCLASSEX wndClass; wndClass.cbClsExtra = 0; wndClass.cbSize = sizeof(WNDCLASSEX); wndClass.cbWndExtra = 0; wndClass.hbrBackground = NULL; wndClass.hCursor = LoadCursor(NULL,IDC_ARROW); wndClass.hIcon = NULL; wndClass.hIconSm = NULL; wndClass.hInstance = hInstance; wndClass.lpfnWndProc=GLWindowProc; wndClass.lpszClassName = L"OpenGL"; wndClass.lpszMenuName = NULL; wndClass.style = CS_VREDRAW | CS_HREDRAW; ATOM atom = RegisterClassEx(&wndClass); RECT rect; rect.left = 0; rect.top = 0; rect.right = 800; rect.bottom = 600; AdjustWindowRect(&rect, WS_OVERLAPPEDWINDOW, FALSE); HWND hwnd = CreateWindowEx(NULL, L"OpenGL", L"RenderWindow", WS_OVERLAPPEDWINDOW, 100, 100, rect.right-rect.left, rect.bottom-rect.top, NULL, NULL, hInstance, NULL); HDC dc = GetDC(hwnd); PIXELFORMATDESCRIPTOR pfd; memset(&pfd, 0, sizeof(PIXELFORMATDESCRIPTOR)); pfd.nVersion = 1; pfd.dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_TYPE_RGBA | PFD_DOUBLEBUFFER; pfd.iLayerType = PFD_MAIN_PLANE; pfd.iPixelType = PFD_TYPE_RGBA; pfd.cColorBits = 32; pfd.cDepthBits = 24; pfd.cStencilBits = 8; int pixelFormatID = ChoosePixelFormat(dc, &pfd); SetPixelFormat(dc,pixelFormatID,&pfd); HGLRC rc = wglCreateContext(dc); wglMakeCurrent(dc, rc); GetClientRect(hwnd, &rect); int viewportWidth = rect.right - rect.left, viewportHeight = rect.bottom - rect.top; glewInit(); GPUProgram fsqProgram; fsqProgram.AttachShader(GL_VERTEX_SHADER, "Debug/res/shader/fullscreenquad.vs"); fsqProgram.AttachShader(GL_FRAGMENT_SHADER, "Debug/res/shader/fullscreenquad.fs"); fsqProgram.Link(); fsqProgram.DetectAttribute("pos"); fsqProgram.DetectAttribute("texcoord"); fsqProgram.DetectUniform("U_MainTexture"); GPUProgram gpuProgram; gpuProgram.AttachShader(GL_VERTEX_SHADER, "Debug/res/shader/Light.vs"); gpuProgram.AttachShader(GL_FRAGMENT_SHADER, "Debug/res/shader/Light.fs"); gpuProgram.Link(); gpuProgram.DetectAttribute("pos"); gpuProgram.DetectAttribute("texcoord"); gpuProgram.DetectAttribute("normal"); gpuProgram.DetectUniform("M"); gpuProgram.DetectUniform("V"); gpuProgram.DetectUniform("P"); gpuProgram.DetectUniform("NM"); gpuProgram.DetectUniform("U_AmbientLightColor"); gpuProgram.DetectUniform("U_AmbientMaterial"); gpuProgram.DetectUniform("U_DiffuseLightColor"); gpuProgram.DetectUniform("U_DiffuseMaterial"); gpuProgram.DetectUniform("U_SpecularLightColor"); gpuProgram.DetectUniform("U_SpecularMaterial"); gpuProgram.DetectUniform("U_LightPos"); gpuProgram.DetectUniform("U_EyePos"); gpuProgram.DetectUniform("U_LightDirection"); gpuProgram.DetectUniform("U_Cutoff"); gpuProgram.DetectUniform("U_DiffuseIntensity"); //init 3d model ObjModel cube; cube.Init("Debug/res/model/Cube.obj"); //摄像机矩阵的单位矩阵 float identity[] = { 1.0f,0,0,0, 0,1.0f,0,0, 0,0,1.0f,0, 0,0,0,1.0f }; float ambientLightColor[] = { 0.4f,0.4f,0.4f,1.0f }; //环境光颜色 float ambientMaterial[] = { 0.2f,0.2f,0.2f,1.0f }; //环境光材质 float diffuseLightColor[] = { 1.0f,1.0f,1.0f,1.0f }; //漫反射光颜色 float diffuseMaterial[] = { 0.6f,0.6f,0.6f,1.0f }; //漫反射光材质 float diffuseIntensity = 1.0f; //漫反射光强度 float specularLightColor[] = { 1.0f,1.0f,1.0f,1.0f }; //环境光颜色 float specularMaterial[] = { 1.0f,1.0f,1.0f,1.0f }; //环境光材质 float lightPos[] = { 0.0f,1.5f,0.0f,0.0f }; //光源位置 float spotLightDirection[] = { 0.0f,-1.0f,0.0f,128.0f }; //聚光灯中心线向量 float spotLightCutoff = 0.0f; // 聚光灯中心线向量和入射光线最大夹角 float eyePos[] = { 0.0f,0.0f,0.0f }; //眼睛的位置 //模型矩阵 glm::mat4 model1 = glm::translate(-2.0f, 0.0f, -6.0f)*glm::rotate(-30.0f,1.0f,1.0f,1.0f); glm::mat4 model2 = glm::translate(0.0f, 0.0f, -6.0f)*glm::rotate(-30.0f,1.0f,1.0f,1.0f); glm::mat4 model3 = glm::translate(2.0f, 0.0f, -6.0f)*glm::rotate(-30.0f,1.0f,1.0f,1.0f); //投影矩阵 glm::mat4 projectionMatrix = glm::perspective(50.0f, (float)viewportWidth / (float)viewportHeight, 0.1f, 1000.0f); //将法线转换到世界空间的变换矩阵 glm::mat4 normalMatrix1 = glm::inverseTranspose(model1); glm::mat4 normalMatrix2 = glm::inverseTranspose(model2); glm::mat4 normalMatrix3 = glm::inverseTranspose(model3); FullScreenQuad fsq; fsq.Init(); FBO fbo; fbo.AttachColorBuffer("color", GL_COLOR_ATTACHMENT0, GL_RGBA, viewportWidth, viewportHeight); fbo.AttachDepthBuffer("depth", viewportWidth, viewportHeight); fbo.Finish(); //glClearColor(41.0f/255.0f,71.0f/255.0f, 121.0f / 255.0f, 1.0f); ShowWindow(hwnd, SW_SHOW); UpdateWindow(hwnd); bool isFullScreen = true; MSG msg; while (true) { if (PeekMessage(&msg,NULL,NULL,NULL,PM_REMOVE)) { if (msg.message==WM_QUIT) { break; } TranslateMessage(&msg); DispatchMessage(&msg); } //绑定fbo----将绘制的场景绑定到FBO fbo.Bind(); glClearColor(0.0f,0.0f,0.0f,1.0f); //这步很重要 glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glEnable(GL_DEPTH_TEST); glUseProgram(gpuProgram.mProgram); //设置shader中变量的值 glUniformMatrix4fv(gpuProgram.GetLocation("V"), 1, GL_FALSE, identity); glUniformMatrix4fv(gpuProgram.GetLocation("P"), 1, GL_FALSE, glm::value_ptr(projectionMatrix)); glUniform4fv(gpuProgram.GetLocation("U_AmbientLightColor"), 1, ambientLightColor); glUniform4fv(gpuProgram.GetLocation("U_AmbientMaterial"), 1, ambientMaterial); glUniform4fv(gpuProgram.GetLocation("U_DiffuseLightColor"), 1, diffuseLightColor); glUniform4fv(gpuProgram.GetLocation("U_DiffuseMaterial"), 1, diffuseMaterial); glUniform4fv(gpuProgram.GetLocation("U_SpecularLightColor"), 1, specularLightColor); glUniform4fv(gpuProgram.GetLocation("U_SpecularMaterial"), 1, specularMaterial); glUniform3fv(gpuProgram.GetLocation("U_EyePos"), 1, eyePos); glUniform4fv(gpuProgram.GetLocation("U_LightDirection"), 1, spotLightDirection); glUniform1f(gpuProgram.GetLocation("U_DiffuseIntensity"), diffuseIntensity); //设置方向光光源的位置 lightPos[0] = 0.0f; lightPos[1] = 1.5f; lightPos[2] = 0.0f; lightPos[3] = 0.0f; //漫反射光照强度 diffuseIntensity = 1.0f; //聚光灯中心线和入射光线最大夹角 spotLightCutoff = 0.0f; //设置shader中变量的值 glUniform4fv(gpuProgram.GetLocation("U_LightPos"), 1, lightPos); glUniform1f(gpuProgram.GetLocation("U_DiffuseIntensity"), diffuseIntensity); glUniform1f(gpuProgram.GetLocation("U_Cutoff"), spotLightCutoff); glUniformMatrix4fv(gpuProgram.GetLocation("M"), 1, GL_FALSE, glm::value_ptr(model1)); glUniformMatrix4fv(gpuProgram.GetLocation("NM"), 1, GL_FALSE, glm::value_ptr(normalMatrix1)); //绘制被方向光照射的立方体 cube.Bind(gpuProgram.GetLocation("pos"), gpuProgram.GetLocation("texcoord"), gpuProgram.GetLocation("normal")); cube.Draw(); //设置点光源的位置 lightPos[0] = 0.0f; lightPos[1] = 3.0f; lightPos[2] = -6.0f; lightPos[3] = 1.0f; diffuseIntensity = 3.0f; //设置shader中变量的值 glUniform4fv(gpuProgram.GetLocation("U_LightPos"), 1, lightPos); glUniform1f(gpuProgram.GetLocation("U_DiffuseIntensity"), diffuseIntensity); glUniformMatrix4fv(gpuProgram.GetLocation("M"), 1, GL_FALSE, glm::value_ptr(model2)); glUniformMatrix4fv(gpuProgram.GetLocation("NM"), 1, GL_FALSE, glm::value_ptr(normalMatrix2)); //绘制被点光源照射的立方体 cube.Bind(gpuProgram.GetLocation("pos"), gpuProgram.GetLocation("texcoord"), gpuProgram.GetLocation("normal")); cube.Draw(); //设置聚光灯的位置 lightPos[0] = 2.0f; lightPos[1] = 3.0f; lightPos[2] = -6.0f; lightPos[3] = 1.0f; diffuseIntensity = 4.0f; spotLightCutoff = 15.0f; //degree glUniform4fv(gpuProgram.GetLocation("U_LightPos"), 1, lightPos); glUniform1f(gpuProgram.GetLocation("U_DiffuseIntensity"), diffuseIntensity); glUniform1f(gpuProgram.GetLocation("U_Cutoff"), spotLightCutoff); glUniformMatrix4fv(gpuProgram.GetLocation("M"), 1, GL_FALSE, glm::value_ptr(model3)); glUniformMatrix4fv(gpuProgram.GetLocation("NM"), 1, GL_FALSE, glm::value_ptr(normalMatrix3)); //绘制被聚光灯照射的立方体 cube.Bind(gpuProgram.GetLocation("pos"), gpuProgram.GetLocation("texcoord"), gpuProgram.GetLocation("normal")); cube.Draw(); glUseProgram(0); glFlush(); fbo.Unbind(); glClearColor(0.1f, 0.4f, 0.7f, 1.0f); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); //这步很重要 glUseProgram(fsqProgram.mProgram); glActiveTexture(GL_TEXTURE0); //将fbo中的内容作为纹理 glBindTexture(GL_TEXTURE_2D,fbo.GetBuffer("color")); glUniform1i(fsqProgram.GetLocation("U_MainTexture"), 0); if (isFullScreen){ //分屏渲染 fsq.DrawToLeftTop(fsqProgram.GetLocation("pos"), fsqProgram.GetLocation("texcoord")); fsq.DrawToLeftBottom(fsqProgram.GetLocation("pos"), fsqProgram.GetLocation("texcoord")); fsq.DrawToRightTop(fsqProgram.GetLocation("pos"), fsqProgram.GetLocation("texcoord")); fsq.DrawToRightBottom(fsqProgram.GetLocation("pos"), fsqProgram.GetLocation("texcoord")); } else //绘制一个充满屏幕的四边形 { fsq.Draw(fsqProgram.GetLocation("pos"), fsqProgram.GetLocation("texcoord")); } glUseProgram(0); glFlush(); SwapBuffers(dc); } return 0; }

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