在GLSL中访问多个FBO纹理以创建另一个纹理

Question

我创建了4个纹理并将它们附加到FBO，名为fbo_texture0 - fbo_texture3。所有这些都已成功创建，如以下屏幕截图所示：

图片1

现在，我想创建使用GLSL从先前纹理（fbo_texture0 - fbo_texture3）获得的第5个纹理。现在，我只想将第一个纹理复制到第五个纹理中。不幸的是，这就是我得到的：

image 2

问题是：

1. 如何在GLSL中访问这些fbo纹理？
2. 我如何创建第5个纹理？ （或从第一个纹理复制到第五个纹理？）

这是程序的完整代码（如果需要）：

    #include <windows.h>
#include <GL/glew.h> // Include the GLEW header file
#include <GL/glut.h> // Include the GLUT header file
#include <iostream> // Allow us to print to the console

using namespace std;

bool* keyStates = new bool[256]; // Create an array of boolean values of length 256 (0-255)

unsigned int fbo; // The frame buffer object
unsigned int fbo_depth; // The depth buffer for the frame buffer object
unsigned int fbo_texture0; // The texture object to write our frame buffer object to
unsigned int fbo_texture1;
unsigned int fbo_texture2;
unsigned int fbo_texture3;
unsigned int fbo_texture4;
GLhandleARB shaderProgram;
GLhandleARB vertexShader;
GLhandleARB fragmentShader;

int window_width = 500; // The width of our window
int window_height = 500; // The height of our window

void initFrameBufferDepthBuffer(void) {
    glGenRenderbuffers(1, &fbo_depth); // Generate one render buffer and store the ID in fbo_depth
    glBindRenderbuffer(GL_RENDERBUFFER, fbo_depth); // Bind the fbo_depth render buffer
    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT, window_width, window_height); // Set the render buffer storage to be a depth component, with a width and height of the window
    glBindRenderbuffer(GL_RENDERBUFFER, 0); // Unbind the render buffer
}

void initFrameBufferTextures(void) {
    glGenTextures(1, &fbo_texture0); // Generate one ture
    glBindTexture(GL_TEXTURE_2D, fbo_texture0); // Bind the ture fbo_texture
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, window_width, window_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL); // Create a standard ture with the width and height of our window
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glBindTexture(GL_TEXTURE_2D, 0);


    glGenTextures(1, &fbo_texture1); // Generate one ture
    glBindTexture(GL_TEXTURE_2D, fbo_texture1); // Bind the ture fbo_texture
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, window_width, window_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL); // Create a standard ture with the width and height of our window
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glBindTexture(GL_TEXTURE_2D, 0);

    glGenTextures(1, &fbo_texture2); // Generate one ture
    glBindTexture(GL_TEXTURE_2D, fbo_texture2); // Bind the ture fbo_texture
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, window_width, window_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL); // Create a standard ture with the width and height of our window
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glBindTexture(GL_TEXTURE_2D, 0);


    glGenTextures(1, &fbo_texture3); // Generate one ture
    glBindTexture(GL_TEXTURE_2D, fbo_texture3); // Bind the ture fbo_texture
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, window_width, window_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL); // Create a standard ture with the width and height of our window
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glBindTexture(GL_TEXTURE_2D, 0);

    glGenTextures(1, &fbo_texture4); // Generate one ture
    glBindTexture(GL_TEXTURE_2D, fbo_texture4); // Bind the ture fbo_texture
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, window_width, window_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL); // Create a standard ture with the width and height of our window
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glBindTexture(GL_TEXTURE_2D, 0);
}

void printInfoLog(GLhandleARB obj)
{
    int infologLength = 0;
    int charsWritten  = 0;
    char* infoLog;

    glGetObjectParameterivARB(obj, GL_OBJECT_INFO_LOG_LENGTH_ARB, &infologLength);
    if (infologLength > 0)
    {
        infoLog = (char*)malloc(infologLength);
        glGetInfoLogARB(obj, infologLength, &charsWritten, infoLog);
        printf("%s\n",infoLog);
        free(infoLog);
    }
}

void initFrameBuffer(void) {
    initFrameBufferDepthBuffer(); // Initialize our frame buffer depth buffer
    initFrameBufferTextures(); // Initialize our frame buffer ture
    glGenFramebuffers(1, &fbo); // Generate one frame buffer and store the ID in fbo
    glBindFramebuffer(GL_FRAMEBUFFER, fbo); // Bind our frame buffer
        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, fbo_texture0, 0);// Attach the ture fbo_texturen to the color buffer in our frame buffer
        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT1, GL_TEXTURE_2D, fbo_texture1, 0);
        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT2, GL_TEXTURE_2D, fbo_texture2, 0); 
        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT3, GL_TEXTURE_2D, fbo_texture3, 0);
        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT4, GL_TEXTURE_2D, fbo_texture4, 0);
        glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, fbo_depth); // Attach the depth buffer fbo_depth to our frame buffer
        GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER); // Check that status of our generated frame buffer
        if (status != GL_FRAMEBUFFER_COMPLETE) // If the frame buffer does not report back as complete
        {
            cout << "Couldn't create frame buffer" << endl; // Output an error to the console
            exit(0); // Exit the application
        }
    glBindFramebuffer(GL_FRAMEBUFFER, 0); // Unbind our frame buffer
}

void init(void) {
    //glEnable(GL_TEXTURE_2D); // Enable turing so we can bind our frame buffer ture
    glEnable(GL_DEPTH_TEST); // Enable depth testing
    initFrameBuffer(); // Create our frame buffer object
}

void keyOperations (void) {
    if (keyStates['a']) { // If the a key has been pressed
        // Perform 'a' key operations
    }
}

void renderTextures(void) {
    glBindFramebuffer(GL_FRAMEBUFFER, fbo); // Bind our frame buffer for rendering
    glPushAttrib(GL_VIEWPORT_BIT | GL_ENABLE_BIT); // Push our glEnable and glViewport states
    glViewport(0, 0, window_width, window_height); // Set the size of the frame buffer view port

    glDrawBuffer(GL_COLOR_ATTACHMENT0);
        glClearColor(0.0f, 0.0f, 0.0f, 1.0f); // Set the clear colour
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);// Clear the depth and colour buffers
        glLoadIdentity();// Reset the modelview matrix
        glTranslatef(0.0f, 0.0f, -5.0f);
       //Add ambient light
        GLfloat ambientColor[] = {0.2f, 0.2f, 0.2f, 1.0f}; //Color(0.2, 0.2, 0.2)
        glLightModelfv(GL_LIGHT_MODEL_AMBIENT, ambientColor);

        //Add positioned light
        GLfloat lightColor0[] = {0.5f, 0.5f, 0.5f, 1.0f}; //Color (0.5, 0.5, 0.5)
        GLfloat lightPos0[] = {4.0f, 0.0f, 8.0f, 1.0f}; //Positioned at (4, 0, 8)
        glLightfv(GL_LIGHT0, GL_DIFFUSE, lightColor0);
        glLightfv(GL_LIGHT0, GL_POSITION, lightPos0);
        //Add directed light
        GLfloat lightColor1[] = {0.5f, 0.2f, 0.2f, 1.0f}; //Color (0.5, 0.2, 0.2)
        //Coming from the direction (-1, 0.5, 0.5)
        GLfloat lightPos1[] = {-1.0f, 0.5f, 0.5f, 0.0f};
        glLightfv(GL_LIGHT1, GL_DIFFUSE, lightColor1);
        glLightfv(GL_LIGHT1, GL_POSITION, lightPos1);
        glEnable(GL_LIGHTING);
        glEnable(GL_LIGHT0);
        glEnable(GL_LIGHT1);
        glEnable(GL_DEPTH_TEST);

        glutSolidTeapot(2.0);
        glColor3f(0.1,0.2,0.7);

    glDrawBuffer(GL_COLOR_ATTACHMENT1);
        glClearColor(0.5f, 0.5f, 0.0f, 1.0f); // Set the clear colour
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);// Clear the depth and colour buffers
        glLoadIdentity();// Reset the modelview matrix
        glTranslatef(0.0f, 0.0f, -5.0f);
        glutSolidTorus(0.80, 1.6, 50, 100);
        glColorMaterial ( GL_FRONT_AND_BACK, GL_EMISSION ) ;
        glEnable ( GL_COLOR_MATERIAL ) ;

    glDrawBuffer(GL_COLOR_ATTACHMENT2);
        glClearColor(0.5f, 0.0f, 0.0f, 1.0f); // Set the clear colour
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);// Clear the depth and colour buffers
        glLoadIdentity();// Reset the modelview matrix
        glTranslatef(0.0f, 0.0f, -2.0f);
        glutSolidTetrahedron();
        glColorMaterial ( GL_FRONT_AND_BACK, GL_EMISSION ) ;
        glEnable ( GL_COLOR_MATERIAL ) ;

    glDrawBuffer(GL_COLOR_ATTACHMENT3);
        glClearColor(0.5f, 0.0f, 0.3f, 1.0f); // Set the clear colour
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);// Clear the depth and colour buffers
        glLoadIdentity();// Reset the modelview matrix
        glTranslatef(0.0f, 0.0f, -2.0f);
        glutSolidOctahedron();
        glColorMaterial ( GL_FRONT_AND_BACK, GL_EMISSION ) ;
        glEnable ( GL_COLOR_MATERIAL ) ;

    glBindFramebuffer(GL_FRAMEBUFFER, 0); // Unbind our ture

    glActiveTexture(GL_TEXTURE0);
    //glEnable(GL_TEXTURE_2D);
    glBindTexture(GL_TEXTURE_2D, fbo_texture0);
    glUniform1i(glGetUniformLocation(shaderProgram, "tex0"), 0);

    glActiveTexture(GL_TEXTURE1);
    //glEnable(GL_TEXTURE_2D);
    glBindTexture(GL_TEXTURE_2D, fbo_texture1);
    glUniform1i(glGetUniformLocation(shaderProgram, "tex1"), 1);

    glActiveTexture(GL_TEXTURE2);
    //glEnable(GL_TEXTURE_2D);
    glBindTexture(GL_TEXTURE_2D, fbo_texture2);
    glUniform1i(glGetUniformLocation(shaderProgram, "tex2"), 2);

    glActiveTexture(GL_TEXTURE3);
    //glEnable(GL_TEXTURE_2D);
    glBindTexture(GL_TEXTURE_2D, fbo_texture3);
    glUniform1i(glGetUniformLocation(shaderProgram, "tex3"), 3);

glPopAttrib(); // Restore our glEnable and glViewport states
glutSwapBuffers();
}

static char* textFileRead(const char *fileName) {
    char* text;

    if (fileName != NULL) {
        FILE *file = fopen(fileName, "rt");

        if (file != NULL) {
            fseek(file, 0, SEEK_END);
            int count = ftell(file);
            rewind(file);

            if (count > 0) {
                text = (char*)malloc(sizeof(char) * (count + 1));
                count = fread(text, sizeof(char), count, file);
                text[count] = '\0';
            }
            fclose(file);
        }
    }
    return text;
}

void initShader(){
    char* vsSource = textFileRead("./shader/multitexture.vs");
    char* fsSource = textFileRead("./shader/multitexture.fs");

    printf("%s\n",fsSource);

    vertexShader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertexShader, 1, (const GLchar **)(&vsSource), NULL);
    glCompileShader(vertexShader);
    printInfoLog(vertexShader);

    fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragmentShader, 1, (const GLchar **)(&fsSource), NULL);
    glCompileShader(fragmentShader);
    printInfoLog(fragmentShader);

    delete [] vsSource;
    delete [] fsSource;

    shaderProgram = glCreateProgram();

    glAttachShader(shaderProgram, vertexShader);
    glAttachShader(shaderProgram, fragmentShader);
    glLinkProgram(shaderProgram);
}



void display (void) {
    keyOperations(); // Perform any key presses
            glUseProgram(0);
    renderTextures(); // Render our teapot scene into our frame buffer
            GLsync s = glFenceSync(GL_SYNC_GPU_COMMANDS_COMPLETE, 0);
            glUseProgram(shaderProgram);
    glClearColor(0.0f, 1.0f, 0.0f, 1.0f); // Clear the background of our window to red
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); //Clear the colour buffer (more buffers later on)
    glLoadIdentity(); // Load the Identity Matrix to reset our drawing locations
    glTranslatef(-4.7f, 1.0f, -4.0f);

    glWaitSync(s, 0, GL_TIMEOUT_IGNORED); 
        glDeleteSync(s);
    glBindTexture(GL_TEXTURE_2D, fbo_texture0); // Bind our frame buffer ture
    glBegin(GL_QUADS);
        glColor4f(1, 1, 1, 1);
        glTexCoord2f(0.0f, 0.0f);
        glVertex3f(-1.0f, -1.0f, 0.0f); // The bottom left corner
        glTexCoord2f(0.0f, 1.0f);
        glVertex3f(-1.0f, 1.0f, 0.0f); // The top left corner
        glTexCoord2f(1.0f, 1.0f);
        glVertex3f(1.0f, 1.0f, 0.0f); // The top right corner
        glTexCoord2f(1.0f, 0.0f);
        glVertex3f(1.0f, -1.0f, 0.0f); // The bottom right corner
    glEnd();
    glBindTexture(GL_TEXTURE_2D, 0); // Unbind any tures

    glLoadIdentity();
    glTranslatef(-2.5f, 1.0f, -4.0f);

    glBindTexture(GL_TEXTURE_2D, fbo_texture1); // Bind our frame buffer ture
        glBegin(GL_QUADS);
            glColor4f(1, 1, 1, 1);
            glTexCoord2f(0.0f, 0.0f);
            glVertex3f(-1.0f, -1.0f, 0.0f); // The bottom left corner
            glTexCoord2f(0.0f, 1.0f);
            glVertex3f(-1.0f, 1.0f, 0.0f); // The top left corner
            glTexCoord2f(1.0f, 1.0f);
            glVertex3f(1.0f, 1.0f, 0.0f); // The top right corner
            glTexCoord2f(1.0f, 0.0f);
            glVertex3f(1.0f, -1.0f, 0.0f); // The bottom right corner
        glEnd();
    glBindTexture(GL_TEXTURE_2D, 0); // Unbind any tures

    glLoadIdentity();
    glTranslatef(-0.3f, 1.0f, -4.0f);

    glBindTexture(GL_TEXTURE_2D, fbo_texture2); // Bind our frame buffer ture
    glBegin(GL_QUADS);
        glColor4f(1, 1, 1, 1);
        glTexCoord2f(0.0f, 0.0f);
        glVertex3f(-1.0f, -1.0f, 0.0f); // The bottom left corner
        glTexCoord2f(0.0f, 1.0f);
        glVertex3f(-1.0f, 1.0f, 0.0f); // The top left corner
        glTexCoord2f(1.0f, 1.0f);
        glVertex3f(1.0f, 1.0f, 0.0f); // The top right corner
        glTexCoord2f(1.0f, 0.0f);
        glVertex3f(1.0f, -1.0f, 0.0f); // The bottom right corner
    glEnd();
    glBindTexture(GL_TEXTURE_2D, 0); // Unbind any tures

    glLoadIdentity();
    glTranslatef(1.9f, 1.0f, -4.0f);

    glBindTexture(GL_TEXTURE_2D, fbo_texture3); // Bind our frame buffer ture
    glBegin(GL_QUADS);
        glColor4f(1, 1, 1, 1);
        glTexCoord2f(0.0f, 0.0f);
        glVertex3f(-1.0f, -1.0f, 0.0f); // The bottom left corner
        glTexCoord2f(0.0f, 1.0f);
        glVertex3f(-1.0f, 1.0f, 0.0f); // The top left corner
        glTexCoord2f(1.0f, 1.0f);
        glVertex3f(1.0f, 1.0f, 0.0f); // The top right corner
        glTexCoord2f(1.0f, 0.0f);
        glVertex3f(1.0f, -1.0f, 0.0f); // The bottom right corner
    glEnd();
    glBindTexture(GL_TEXTURE_2D, 0); // Unbind any tures

    glLoadIdentity();
    glTranslatef(4.1f, 1.0f, -4.0f);

    glBindTexture(GL_TEXTURE_2D, fbo_texture4); // Bind our frame buffer ture
    glBegin(GL_QUADS);
        glColor4f(1, 1, 1, 1);
        glTexCoord2f(0.0f, 0.0f);
        glVertex3f(-1.0f, -1.0f, 0.0f); // The bottom left corner
        glTexCoord2f(0.0f, 1.0f);
        glVertex3f(-1.0f, 1.0f, 0.0f); // The top left corner
        glTexCoord2f(1.0f, 1.0f);
        glVertex3f(1.0f, 1.0f, 0.0f); // The top right corner
        glTexCoord2f(1.0f, 0.0f);
        glVertex3f(1.0f, -1.0f, 0.0f); // The bottom right corner
    glEnd();
    glBindTexture(GL_TEXTURE_2D, 0); // Unbind any tures

    glutSwapBuffers();
}

void reshape (int width, int height) {
    glViewport(0, 0, (GLsizei)width, (GLsizei)height); // Set our viewport to the size of our window
    glMatrixMode(GL_PROJECTION); // Switch to the projection matrix so that we can manipulate how our scene is viewed
    glLoadIdentity(); // Reset the projection matrix to the identity matrix so that we don't get any artifacts (cleaning up)
    gluPerspective(60, (GLfloat)width / (GLfloat)height, 1.0, 100.0); // Set the Field of view angle (in degrees), the aspect ratio of our window, and the new and far planes
    glMatrixMode(GL_MODELVIEW); // Switch back to the model view matrix, so that we can start drawing shapes correctly
}

void keyPressed (unsigned char key, int x, int y) {
    keyStates[key] = true; // Set the state of the current key to pressed
}

void keyUp (unsigned char key, int x, int y) {
    keyStates[key] = false; // Set the state of the current key to not pressed
}

int main (int argc, char **argv) {
    glutInit(&argc, argv); // Initialize GLUT
    glutInitDisplayMode (GLUT_DOUBLE | GLUT_DEPTH | GLUT_RGBA); // Set up a basic display buffer (only single buffered for now)
    glutInitWindowSize (1280, 500); // Set the width and height of the window
    glutInitWindowPosition (100, 100); // Set the position of the window
    glutCreateWindow ("OpenGL FBO"); // Set the title for the window

    if (GLEW_OK != glewInit()) {
        std::cout << "Couldn't initialize GLEW" << std::endl;
        exit(0);
    }
    initShader();
    init();

    glutDisplayFunc(display); // Tell GLUT to use the method "display" for rendering
    glutIdleFunc(display); // Tell GLUT to use the method "display" for rendering
    glutReshapeFunc(reshape); // Tell GLUT to use the method "reshape" for reshaping
    glutKeyboardFunc(keyPressed); // Tell GLUT to use the method "keyPressed" for key presses
    glutKeyboardUpFunc(keyUp); // Tell GLUT to use the method "keyUp" for key up events
    glutMainLoop(); // Enter GLUT's main loop
}

这是顶点着色器：

void main(void) 
{ 
    gl_TexCoord[0] = gl_MultiTexCoord0;
    gl_Position = ftransform();
}

这是片段着色器：

uniform sampler2D tex0;
uniform sampler2D tex1;
uniform sampler2D tex2;
uniform sampler2D tex3;

void main(void) 
{ 
    gl_FragColor = texture2D(tex0, gl_TexCoord[0].st);
}

编辑＃1

根据@Damon的建议修改代码（代码也已经编辑过），这里是结果的截图：

image 3

现在，我真的不知道问题究竟是什么。我试图更改片段着色器以访问另一个纹理，例如gl_FragColor = texture2D(tex2, gl_TexCoord[0].st);但我仍然得到与上面相同的显示。所以我认为这绝对不是模型视图/投影问题。

编辑＃2

问题仍然不明朗。但是，我试图在程序中只给出一个glActiveTexture(GL_TEXTUREn);命令，并注释掉其他glActiveTexture命令（没有着色器修改），并得到以下结果：

image 4 仅激活了glActiveTexture(GL_TEXTURE0);。

image 5 仅激活glActiveTexture(GL_TEXTURE1);。

image 6 仅激活glActiveTexture(GL_TEXTURE2);。

image 7 仅激活glActiveTexture(GL_TEXTURE3);。

当激活至少2 glActiveTexture(GL_TEXTUREn);时，我得到的结果与 image 5 相同。这让我想知道问题究竟是什么。

Answer 1

initShader编译并链接着色器。您似乎也以一种正常的方式将纹理绑定到renderTextures中的纹理单元（解除FBO绑定后，这对于同步非常重要）。到目前为止一直很好，但我在代码中的任何地方都找不到glUseProgram。这意味着渲染会回落到固定函数，当时没有任何纹理绑定。

片段着色器只能从tex0读取，所以当然你不会期望看到tex1-tex3（但我想这只是最小的工作示例代码）。

除此之外，通过在5分钟内阅读代码，我可以看到它看起来不错。

（作为旁注：init调用glEnable(GL_TEXTURE_2D)，这并非严格错误，但只要您使用着色器就无用，请参阅this。）