GLSL / OpenGL FBO不会解除绑定

Question

最近，我一直在尝试学习现代OpenGL / GLSL，这使我进入了FBO的主题，并且遇到了一个神秘的问题。

在程序中，我初始化了一个FBO，然后将其解除绑定。 到目前为止一切正常。 然后，我绑定FBO，并对其渲染场景。 现在，当我运行该程序时，我得到一个空白屏幕，但这很正常-我没有渲染输出。 但是，当我尝试执行此操作或尝试渲染所有内容时，仍然会出现黑屏。 只有在主循环中不绑定FBO时，我才能使它起作用。 我有使用LWJGL在Java中工作的FBO，这是我第二次尝试使用SDL在C ++中渲染FBO，并且两次都遇到相同的错误。

不是什么：

• 纹理-使用FBO后我已经尝试绘制其他纹理
• 着色器-我已经在此尝试了其他着色器
• 我使用的包装器类-已经证明它们在使用其他系统时都可以工作。

另外，glChackFramebufferStatus（GL_FRAMEBUFFER）返回GL_FRAMEBUFFER_COMPLETE，而glGetError（）返回0。另外，我知道我还没有做过一些有意义的事情（例如，深度缓冲区），不会影响此错误。 我将在后面填写。

这是代码：Main.cpp：

#include <iostream>
#include "GLee.h"
#define GLM_FORCE_RADIANS
#include "matrices.h" //Replaces built-in matrices, functions behave the same as legacy OGL
#include "functions.h" //Camera, works very well
#include <SDL/SDL.h>
#include <SDL/SDL_image.h>


#include <SDL/SDL_opengl.h>
#include <SDL/SDL_mouse.h>

#include <math.h>
#include <SDL/SDL_opengl.h>
#include <vector>
#include <string>
#include <algorithm>
#include <fstream>
#include <cstdio>
#include <cstdlib>




#include <GL/gl.h>
#include <GL/glu.h>


//#include <SDL/SDL_video.h>

using namespace std;

unsigned int grass, crate, FBOTex;
int ground, monkey;
bool mousein = true;
matrices pipeline;
int frame;

#include <GL/gl.h>
#include <GL/glu.h>
#include "TexLoader.h" //Loads textures - I've never had issues with this header
#include "ModelLoader.h" //Loads models (OBJ), again, works like a treat
#include "shader.h" //Includes the shader class, which has been proven to work
#include "Material.h" //Used in lighting calculations

texProperties linear = texProperties(GL_LINEAR, GL_LINEAR_MIPMAP_LINEAR, GL_REPEAT, 16);
texProperties pixellated = texProperties(GL_NEAREST, GL_LINEAR_MIPMAP_LINEAR, GL_REPEAT, 16); //Properties for textures loaded by the texture loader.

shader* mainShader;
shader* postProcess; //The FBO shader
material simpleMaterial = material(0.2, 0.2, 0.2, 0.6, 0.6, 0.6, 0.1,0.1,0.1, 1000),
littleShine = material(0.2, 0.2, 0.2, 0.6, 0.6, 0.6, 0.1,0.1,0.1, 5),
monkeyMtl = material(0.2, 0.2, 0.2, 0.6, 0.6, 0.6, 0.3,0.3,0.3, 50);
//monkeyMtl = material(0.2, 0.2, 0.2, 0.6, 0.6, 0.6, 1,1,1, 5);

SDL_Surface* loadTextureData(const char* fileName){ //For creating icons
    SDL_Surface* tex;
    if((tex = IMG_Load(fileName))){
        cout<<"Texture Found! Tex: "<<fileName<<endl;
    }
    return tex;
}

unsigned int createTexture(int w, int h, bool isDepth){ //Create texture for FBO
    unsigned int textureID;
    glGenTextures(1, &textureID);
    glBindTexture(GL_TEXTURE_2D, textureID);
    glTexImage2D(GL_TEXTURE_2D, 0, isDepth?GL_DEPTH_COMPONENT:GL_RGBA8, w, h, 0, isDepth?GL_DEPTH_COMPONENT:GL_RGBA, GL_FLOAT, NULL);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    int i;
    i = glGetError();
    if(i != 0){
        cout<<"Texture creation error! Error code: "<<i<<endl;
    }
    glBindTexture(GL_TEXTURE_2D, 0);
    return textureID;
}

unsigned int fbo; //The FBO ID
unsigned int renderTexture; //The ID of the output texture for the FBO 

void init(){
    //glEnable(GL_CULL_FACE);
    //glCullFace(GL_BACK);
    const unsigned char* text = glGetString(GL_VERSION); //OpenGL 4
    cout<<"GL version: "<<text<<endl;
    SDL_WM_GrabInput(SDL_GRAB_ON);
    glEnable(GL_MULTISAMPLE);
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_TEXTURE_2D);
    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    SDL_GL_SetAttribute(SDL_GL_MULTISAMPLEBUFFERS, 1);
    SDL_GL_SetAttribute(SDL_GL_MULTISAMPLESAMPLES, 8);
    SDL_WM_SetCaption("OGL!", "OGL!!");
    //SDL_WM_IconifyWindow();
    SDL_Surface* icon = loadTextureData("Logo.png");
    SDL_WM_SetIcon(icon, NULL);
    glClearColor(0.0, 0.0, 0.0, 1);
    pipeline.matrixMode(PROJECTION_MATRIX);
    pipeline.loadIdentity();

    pipeline.perspective(45, 1280.0/720.0, 0.1, 5000.0); //Similar to legacy OGL
    pipeline.matrixMode(MODEL_MATRIX);

    SDL_FreeSurface(icon);

    mainShader = new shader("vertex.vert", "fragment.frag"); //These shader files         load+compile fine
    postProcess = new shader("PostProcess.vert", "PostProcess.frag");
    grass = getTexture("Textures/Grass.png", linear);
    crate = getTexture("Textures/Crate.png", linear);
    ground = loadModel("Models/Plane.obj");
    monkey = loadModel("Models/Monkey.obj");
    float amb[3]  {0.2, 0.2, 0.2};
    float diff[3]  {0.6, 0.6, 0.6};
    float spec[3]  {1, 1, 1};

    //////////FBO Creation///////////
    glGenFramebuffers(1, &fbo);
    glBindFramebuffer(GL_FRAMEBUFFER, fbo);//This bind function works
    renderTexture = createTexture(1920, 1080, false);
    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, renderTexture, 0);

    int i = glCheckFramebufferStatus(GL_FRAMEBUFFER);
    if(i != GL_FRAMEBUFFER_COMPLETE){//I get no errors here...
        cout<<"FBO is not complete!"<<endl;
    }
    cout<<"glGetError() = "<<glGetError()<<endl; //Prints 0
    glBindFramebuffer(GL_FRAMEBUFFER, 0); //This unbind works perfectly
}

void display(){ //The drawing part of the main loop
    cout<<"FBO Number: "<<fbo<<endl; //Returns 1, as it should
    glBindFramebuffer(GL_FRAMEBUFFER, fbo); 
    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
    mainShader->bindShader();
    mainShader->setUniformFloat3("lspecular", 1,1,1); //Lighting stuff...
    mainShader->setUniformFloat3("lambient", 0.2,0.2,0.2);
    mainShader->setUniformFloat3("ldiffuse", 0.6,0.6,0.6);

    mainShader->setUniformFloat3("lightPos", 0,500,0);
    mainShader->setUniformSampler("texture", 0);
    mainShader->setUniformFloat("constantAttenuation", 0.0);
    mainShader->setUniformFloat("linearAttenuation", 0.0);
    mainShader->setUniformFloat("quadraticAttenuation", 0.000002);
    littleShine.addToShader(*mainShader); //Sets material for lighting
    pipeline.matrixMode(PROJECTION_MATRIX);
    pipeline.loadIdentity();
    pipeline.perspective(45, 1280.0/720.0, 0.1, 5000.0); //3D projection
    pipeline.matrixMode(VIEW_MATRIX);
    pipeline.loadIdentity();
    control(0.2, 0.2, mousein, pipeline); //Controls camera
    updateCamera(pipeline); //Updates matrices
    pipeline.updateMatrices(mainShader->getHandle()); //Updates shader matrices
    glBindTexture(GL_TEXTURE_2D, grass);
    pipeline.matrixMode(MODEL_MATRIX);
    //pipeline.loadIdentity();

    glCallList(ground);

    pipeline.translate(0, 1, -5);
    pipeline.rotatef(frame, 0, 1, 0);
    pipeline.updateMatrices(mainShader->getHandle());
    monkeyMtl.addToShader(*mainShader);
    glBindTexture(GL_TEXTURE_2D, crate);
    glCallList(monkey);

    glBindFramebuffer(GL_FRAMEBUFFER, 0); ///////DOESN'T UNBIND!! Still get black screen
    //glClear(GL_COLOR_BUFFER_BIT);
    pipeline.matrixMode(MODEL_MATRIX);
    pipeline.loadIdentity();
    pipeline.matrixMode(VIEW_MATRIX);
    pipeline.loadIdentity();
    //pipeline.translate(0, 0, -5);
    pipeline.matrixMode(PROJECTION_MATRIX);
    pipeline.loadIdentity();
    pipeline.ortho(1920, 0, 0, 1080, 1, -1);//Clear matrices, set orthographic view
    //mainShader->unbindShader();
    postProcess->bindShader(); //Binds the post-processing shader
    postProcess->setUniformSampler("texture", 0); //Texture sampler
    pipeline.updateMatrices(postProcess->getHandle());
    glBindTexture(GL_TEXTURE_2D, renderTexture); //Bind the FBO's output as a texture
    glBindFramebuffer(GL_FRAMEBUFFER, 0); //Tried a second time to unbind FBO, to no avail...
    glBegin(GL_QUADS);

    glColor3f(1.0, 1.0, 1.0); //Makes no difference
        glTexCoord2f(0,0);      /////Draw FBO texture to screen, fails
        glVertex2f(0,0);                               
        glTexCoord2f(1,0);
        glVertex2f(1920,0);
        glTexCoord2f(1,1);
        glVertex2f(1920,1080);
        glTexCoord2f(0,1);
        glVertex2f(0,1080);
    glEnd();

}
void update(){
    frame++;
}

int main(int args, char* argv[]){
    SDL_Init(SDL_INIT_EVERYTHING);
    IMG_Init(IMG_INIT_PNG);
    SDL_Delay(150);
    SDL_GL_SetAttribute(SDL_GL_MULTISAMPLEBUFFERS, 1);
    SDL_GL_SetAttribute(SDL_GL_MULTISAMPLESAMPLES, 8);
    SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
    SDL_Surface* screen = SDL_SetVideoMode(1920, 1080, 32, SDL_SWSURFACE|SDL_OPENGL|SDL_FULLSCREEN);

    bool running = true;
    Uint32 start;
    SDL_Event event;
    init();
    while(running){
        start = SDL_GetTicks();
        while(SDL_PollEvent(&event)){
            switch(event.type){
            case SDL_QUIT:
                running = false;
            break;
            case SDL_KEYDOWN:
            switch(event.key.keysym.sym){
            default:
                break;
                case SDLK_ESCAPE:
                    running = false;
                break;
                case SDLK_p:
                    mousein = false;
                    SDL_ShowCursor(SDL_ENABLE);
                    SDL_WM_GrabInput(SDL_GRAB_OFF);
                    break;
            }
                break;
            case SDL_KEYUP:

                break;
            case SDL_MOUSEBUTTONDOWN:
                mousein = true;
                SDL_ShowCursor(SDL_DISABLE);
                SDL_WM_GrabInput(SDL_GRAB_ON);
                break;
            }
        }
        update();
        display();
        SDL_GL_SwapBuffers();
        if(1000/60 > (SDL_GetTicks() - start)){
            SDL_Delay(1000/60 - (SDL_GetTicks() - start));
        }
    }
    delete mainShader;
    SDL_Quit();
    //cout << "Hello world!" << endl;
    return 0;
}

PostProcess.vert：

#version 130
varying vec2 texCoord;
varying vec3 position;
varying vec3 normal;
//Matrices, passed in to shader
uniform mat4 modelMatrix;
uniform mat4 viewMatrix;
uniform mat4 projectionMatrix;
uniform mat4 modelViewMatrix;
uniform mat4 modelViewProjectionMatrix;
uniform mat3 normalMatrix;


void main(){
    gl_Position = modelViewProjectionMatrix * gl_Vertex;
    normal = normalMatrix * gl_Normal;
    texCoord = gl_MultiTexCoord0.st;
    position = vec3(modelViewMatrix * gl_Vertex);
}

PostProcess.frag：

#version 130
uniform sampler2D texture;
varying vec2 texCoord;
varying vec3 position;
varying vec3 normal;

void main(){
    gl_FragColor = texture(texture, texCoord); //Draw the textur, also tried texture2D...
    //gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0); //I've tried drawing white to the screen - it failed
}

我真的不知道这里发生了什么。 我猜这很简单，但是我怎么错过了两次呢？

Answer 1

我已经解决了！

由于某种原因，material.cpp文件将所有内容弄乱了。 由于某些原因，当我使用material.addToShader（shader）函数时，它不会渲染，但是当我自己添加制服或将参数更改为指向着色器的指针时，它似乎工作得很好。 此问题引起了1281错误。 我为什么不知道为什么会这样，但至少现在已经解决了！

Answer 2

绑定窗口帧缓冲区时，不要调用glClear。 尝试：

glBindFramebuffer(GL_FRAMEBUFFER, 0);

glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);