objective-c – 两个FBO之间的乒乓渲染在第一帧之后失败.

编辑

也许我没有清楚地描述.实际上,我想使用textureB作为纹理并将其渲染为textureA,然后使用textureA渲染到屏幕,反之亦然.

编辑
我可以看到第一帧,即textureB.经过片段着色器后,它变为黑色.首先,我怀疑片段着色器,我将其更改为仅将黑色恢复为白色,将白色恢复为黑色.它仍然变得全黑.

设置fbo和纹理

glEnable(GL_TEXTURE_2D);
    glGenTextures(1,&textureA);
    glBindTexture(GL_TEXTURE_2D,textureA);
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
    glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S,GL_CLAMP_TO_EDGE);
    glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_WRAP_T,GL_CLAMP_TO_EDGE);
    glTexImage2D(GL_TEXTURE_2D,GL_RGBA,256,GL_UNSIGNED_BYTE,NULL);

    glGenTextures(1,&textureB);
    glBindTexture(GL_TEXTURE_2D,textureB);
    glTexParameteri(GL_TEXTURE_2D,GL_CLAMP_TO_EDGE);

    data=(GLubyte*)malloc(256*256*4*sizeof(GLubyte));
    GLubyte val;
    for (int i = 0; i < 256 * 256 * 4; i+=4) {   
        if (rand()%10 ==1) 
            { val = 0; } 
        else 
            { val = 255; }
        data[i] = data[i+1] = data[i+2] = val;
        data[i+3] = 255;
    }
    glTexImage2D(GL_TEXTURE_2D,data);

    glGenFramebuffers(1,&fboA);
    glBindFramebuffer(GL_FRAMEBUFFER,fboA);
    glFramebufferTexture2D(GL_FRAMEBUFFER,GL_COLOR_ATTACHMENT0,GL_TEXTURE_2D,textureA,0);

    glGenFramebuffers(1,&fboB);
    glBindFramebuffer(GL_FRAMEBUFFER,fboB);
    glFramebufferTexture2D(GL_FRAMEBUFFER,textureB,0);

渲染循环

if ([context API] == kEAGLRenderingAPIOpenGLES2) {


        if(counter%2==0)
        {
            glUseProgram(automateProg);
            glBindFramebuffer(GL_FRAMEBUFFER,fboA);
            glActiveTexture(GL_TEXTURE0);
            glBindTexture(GL_TEXTURE_2D,textureB);
            glUniform1i(AUTOMATE_TEXT,0);
            glUniform1f(DU,1.0/256);
            glUniform1f(DV,1.0/256);
            // Update attribute values.
            glVertexAttribPointer(ATTRIB_VERTEX_2,2,GL_FLOAT,squareVertices);
            glEnableVertexAttribArray(ATTRIB_VERTEX_2);

            glVertexAttribPointer(ATTRIB_TEXCOORD_2,GL_FALSE,texCoord);    
            //glEnableVertexAttribArray(ATTRIB_TEXCOORD_2);
            glDrawArrays(GL_TRIANGLE_STRIP,4);
            if (![self validateProgram:automateProg]) {
                NSLog(@"Failed to validate program: %d",automateProg);
                return;
            }

            glBindFramebuffer(GL_FRAMEBUFFER,0);
            glUseProgram(0);
        }
        else
        {
            glUseProgram(automateProg);            
            glBindFramebuffer(GL_FRAMEBUFFER,fboB);
            glActiveTexture(GL_TEXTURE0);
            glBindTexture(GL_TEXTURE_2D,textureA);
            glUniform1i(AUTOMATE_TEXT,squareVertices);
            glEnableVertexAttribArray(ATTRIB_VERTEX_2);
            glVertexAttribPointer(ATTRIB_TEXCOORD_2,texCoord); 
            //glEnableVertexAttribArray(ATTRIB_TEXCOORD_2);
            glDrawArrays(GL_TRIANGLE_STRIP,0);
            glUseProgram(0);
        }

        [(EAGLView *)self.view setFramebuffer];
        glClearColor(0.5f,0.5f,1.0f);
        glClear(GL_COLOR_BUFFER_BIT);

        if (counter % 2 == 0) {
            glUseProgram(normalProg);
            glActiveTexture(GL_TEXTURE0);
            glBindTexture(GL_TEXTURE_2D,textureB);
            glUniform1i(NORMAL_TEXT,0);
            glVertexAttribPointer(ATTRIB_VERTEX,squareVertices);
            glEnableVertexAttribArray(ATTRIB_VERTEX);
            glVertexAttribPointer(ATTRIB_TEXCOORD,texCoord); 
            glEnableVertexAttribArray(ATTRIB_TEXCOORD);
            glDrawArrays(GL_TRIANGLE_STRIP,4);
            if (![self validateProgram:normalProg]) {
                NSLog(@"Failed to validate program: %d",normalProg);
                return;
            }
            glUseProgram(0);

        } else {
            glUseProgram(normalProg);
            glActiveTexture(GL_TEXTURE0);
            glBindTexture(GL_TEXTURE_2D,textureA);
            glUniform1i(NORMAL_TEXT,normalProg);
                return;
            }
            glUseProgram(0);
        }
        counter++;

[(EAGLView *)self.view presentFramebuffer];

片段着色器

precision mediump float;
varying vec2 v_texCoord;
uniform sampler2D tex; //the input texture
uniform float du; //the width of the cells
uniform float dv; //the height of the cells
    void main() {
        int count = 0;

        vec4 C = texture2D( tex,v_texCoord );
        vec4 E = texture2D( tex,vec2(v_texCoord.x + du,v_texCoord.y) );
        vec4 N = texture2D( tex,vec2(v_texCoord.x,v_texCoord.y + dv) );
        vec4 W = texture2D( tex,vec2(v_texCoord.x - du,v_texCoord.y) );
        vec4 S = texture2D( tex,v_texCoord.y - dv) );
        vec4 NE = texture2D( tex,v_texCoord.y + dv) );
        vec4 NW = texture2D( tex,v_texCoord.y + dv) );
        vec4 SE = texture2D( tex,v_texCoord.y - dv) );
        vec4 SW = texture2D( tex,v_texCoord.y - dv) );

        if (E.r == 1.0) { count++; }
        if (N.r == 1.0) { count++; }
        if (W.r == 1.0) { count++; }
        if (S.r == 1.0) { count++; }
        if (NE.r == 1.0) { count++; }
        if (NW.r == 1.0) { count++; }
        if (SE.r == 1.0) { count++; }
        if (SW.r == 1.0) { count++; }

        if ( (count == 2 || count == 3)) {
            gl_FragColor = vec4(1.0,1.0,1.0); //cell lives...
        } else {
            gl_FragColor = vec4(0.0,0.0,1.0); //cell dies...
        }
    }