Border of Alpha-Blended Textures get black

[thestr4ng3r]

I am rendering a scene to a texture using an fbo and then I render this texture to another one using a gaussian blur shader. But after that, the borders of all faces that are alpha blended get black. Here are some screenshots:
Before...:
http://i.stack.imgur.com/fgjxQ.jpg
..and after going through the blur (blur size is set to 0 in this case)
http://i.stack.imgur.com/tq94C.jpg

This is where the textures are created:

glGenTextures(1, &render.color_tex);
glBindTexture(GL_TEXTURE_2D, render.color_tex);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_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);
glTexParameteri(GL_TEXTURE_2D, GL_GENERATE_MIPMAP, GL_TRUE);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, display_width * render.aa_level, display_height * render.aa_level, 0, GL_RGBA, GL_UNSIGNED_BYTE, 0);
glBindTexture(GL_TEXTURE_2D, 0);
 
glGenTextures(1, &render.color_tex_temp);
glBindTexture(GL_TEXTURE_2D, render.color_tex_temp);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_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);
glTexParameteri(GL_TEXTURE_2D, GL_GENERATE_MIPMAP, GL_TRUE);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, display_width * render.aa_level, display_height * render.aa_level, 0, GL_RGBA, GL_UNSIGNED_BYTE, 0);
glBindTexture(GL_TEXTURE_2D, 0);
 
glGenTextures(1, &render.color_tex_blurred);
glBindTexture(GL_TEXTURE_2D, render.color_tex_blurred);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_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);
glTexParameteri(GL_TEXTURE_2D, GL_GENERATE_MIPMAP, GL_TRUE);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, display_width * render.aa_level, display_height * render.aa_level, 0, GL_RGBA, GL_UNSIGNED_BYTE, 0);
glBindTexture(GL_TEXTURE_2D, 0);

The function that blurs the rendered texture:

void CGame::BlurTexture(GLuint in, GLuint temp, GLuint out, int width, int height, float size)
{
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, blur.fbo);
    glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, temp, 0);
 
    glDisable(GL_LIGHTING);
    glDisable(GL_DEPTH_TEST);
    glViewport(0, 0, width, height);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0.0, 0.0, 1.0, 1.0, -1.0, 1.0);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
 
    blur_shader.BindShader();
    blur_shader.SetBlur(size, BLUR_VERTICAL);
    blur_shader.SetTexture(in, display_width, display_height);
 
    glColor4f(1.0, 1.0, 1.0, 1.0);
    glBegin(GL_QUADS);
        blur_shader.SetTexCoord(Vec(0.0, 1.0));
        glVertex2f(-1.0, 1.0);
 
        blur_shader.SetTexCoord(Vec(0.0, 0.0));
        glVertex2f(-1.0, -1.0);
 
        blur_shader.SetTexCoord(Vec(1.0, 0.0));
        glVertex2f(1.0, -1.0);
 
        blur_shader.SetTexCoord(Vec(1.0, 1.0));
        glVertex2f(1.0, 1.0);
    glEnd();
 
    UseNoShader();
 
    glFlush();
 
    glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, out, 0);
 
    glDisable(GL_LIGHTING);
    glDisable(GL_DEPTH_TEST);
    glViewport(0, 0, width, height);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0.0, 0.0, 1.0, 1.0, -1.0, 1.0);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
 
    blur_shader.BindShader();
    blur_shader.SetBlur(size, BLUR_HORIZONTAL);
    blur_shader.SetTexture(temp, display_width, display_height);
 
    glColor4f(1.0, 1.0, 1.0, 1.0);
    glBegin(GL_QUADS);
        blur_shader.SetTexCoord(Vec(0.0, 1.0));
        glVertex2f(-1.0, 1.0);
 
        blur_shader.SetTexCoord(Vec(0.0, 0.0));
        glVertex2f(-1.0, -1.0);
 
        blur_shader.SetTexCoord(Vec(1.0, 0.0));
        glVertex2f(1.0, -1.0);
 
        blur_shader.SetTexCoord(Vec(1.0, 1.0));
        glVertex2f(1.0, 1.0);
    glEnd();
 
    UseNoShader();
 
    glFlush();
 
    glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, 0, 0);
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
 
    glActiveTextureARB(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, out);
    glGenerateMipmapEXT(GL_TEXTURE_2D);
    glBindTexture(GL_TEXTURE_2D, 0);
}

And finally how the function is called:

BlurTexture(render.color_tex, render.color_tex_temp, render.color_tex_blurred,
            display_width * render.aa_level, display_height * render.aa_level, 0.0

By the way, it is NOT the fault of the shader. I used the fixed functionality and the issue was still present