glsl - fragment-shader (blur) -> black screen

Question

I've been trying to get this to work for the last few days and I'm really starting to become desperate. I'd be really grateful for suggestions you might have.

What I've been trying to do:

• render the scene to an FBO
• blur the attached texture using glsl shaders
• render the resulting texture to a screen aligned quad

Issue:

If I enable the fragment-shader (horizontal blur) i do get a blurred image rendered to my quad for the first frame or so, after that it's all black.

My suspicion is that there i something wrong with the way I'm passing the texture to my shader:

    horizontalBlurVertex.enable();

    horizontalBlurFragment.enable();

    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, fboTexture);
    glUniform1i(glGetUniformLocation(horizontalBlurFragment.program, "RTScene"), 0);

EDIT: One more piece of Information: if i remove glUniform1i(glGetUniformLocation(horizontalBlurFragment.program, "RTScene"), 0); i get the exact same result. Which i guess indicates that my shader never gets any texture data whatsoever.

sources:

vertex-shader:

varying vec2 vTexCoord;

void main(void)
{
   gl_FrontColor = gl_Color;
   gl_Position = ftransform();

   vec2 Pos;
   Pos = sign(gl_Vertex.xy);

   gl_Position = vec4(Pos, 0.0, 1.0);

   vTexCoord = Pos * 0.5 + 0.5;
}

fragment-shader:

uniform sampler2D RTScene;
varying vec2 vTexCoord;

const float blurSize = 1.0/800.0;
const float weightSum = 70.0 + 2.0 * (1.0 + 8.0 + 28.0 + 56.0);

void main(void)
{
   vec4 sum = vec4(0.0);

   sum += texture2D(RTScene, vec2(vTexCoord.x - 4.0*blurSize, vTexCoord.y)) * 1.0 / weightSum;
   sum += texture2D(RTScene, vec2(vTexCoord.x - 3.0*blurSize, vTexCoord.y)) * 8.0 / weightSum;
   sum += texture2D(RTScene, vec2(vTexCoord.x - 2.0*blurSize, vTexCoord.y)) * 28.0 / weightSum;
   sum += texture2D(RTScene, vec2(vTexCoord.x - blurSize, vTexCoord.y)) * 56.0 / weightSum;
   sum += texture2D(RTScene, vec2(vTexCoord.x, vTexCoord.y)) * 70.0 / weightSum;
   sum += texture2D(RTScene, vec2(vTexCoord.x + blurSize, vTexCoord.y)) * 56.0 / weightSum;
   sum += texture2D(RTScene, vec2(vTexCoord.x + 2.0*blurSize, vTexCoord.y)) * 28.0 / weightSum;
   sum += texture2D(RTScene, vec2(vTexCoord.x + 3.0*blurSize, vTexCoord.y)) * 8.0 / weightSum;
   sum += texture2D(RTScene, vec2(vTexCoord.x + 4.0*blurSize, vTexCoord.y)) * 1.0 / weightSum;

   gl_FragColor = sum;
}

render to fbo:

//handels
    GLuint fbo, fboTexture, fboDepthbuffer;

    // generate namespace for the frame buffer, colorbuffer and depthbuffer
    glGenFramebuffersEXT(1, &fbo);
    glGenTextures(1, &fboTexture);
    glGenRenderbuffersEXT(1, &fboDepthbuffer);

    //switch to our fbo so we can bind stuff to it
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo);

    //create the colorbuffer texture and attach it to the frame buffer
    glGenTextures(1, &fboTexture);
    glBindTexture(GL_TEXTURE_2D, fboTexture);
    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_MAG_FILTER, GL_LINEAR);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
    glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT,GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, fboTexture, 0);

    // create a render buffer as our depthbuffer and attach it
    glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, fboDepthbuffer);
    glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_DEPTH_COMPONENT24, width, height);
    glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT, GL_RENDERBUFFER_EXT, fboDepthbuffer);

    // Go back to regular frame buffer rendering
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);

    glBindTexture(GL_TEXTURE_2D, 0);
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo);
        glPushAttrib(GL_VIEWPORT_BIT);
            glViewport(0, 0, width, height);
            glPushMatrix();
                glBegin(GL_QUADS);
                    glNormal3f(0.0, 0.0, 1.0);

                    glColor3f(1.0f, 1.0f, 0.0f);
                    glVertex3f(-0.1, 0.1, -1.0);

                    glColor3f(1.0f, 0.0f, 0.0f);
                    glVertex3f(0.1, 0.1, -1.0);

                    glColor3f(0.0f, 1.0f, 0.0f);
                    glVertex3f(0.1, -0.1, -1.0);

                    glColor3f(0.0f, 0.0f, 1.0f);
                    glVertex3f(-0.1, -0.1, -1.0);
                glEnd();
            glPopMatrix();
        glPopAttrib();
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);

(not posting my ShaderLoader source here since using simpler shaders (switching colors and whatnot) works perfectly fine)

If you think the error lies somewhere else I'll be happy to post some additional code.

Answer 1

Problem solved!

Turns out I foolishly created my fbo every frame... works perfectly fine now.