Odd blending result (semi-transparent 2d quad over 3D scene)

Question

I'm working on a GUI library for my game, and I'm having problems with my blending.

I have a 3D scene, which I render with glDrawArrays. In the fragment shader the alpha color is hardcoded 1.0f (gl_FragColor).

When I render a 2D quad on my screen with 1.0f in the alpha channel, my quad is semi-transparent, while it should be completely opaque.

I render the quad with the basic glBegin(GL_QUADS) and glColor4f(0.0f, 0.0f, 1.0f, 1.0f).

I enabled blending with the function:

glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

What am I doing wrong? Why is my quad semi-transparent?

Screenshot:

Fragment shader:

#version 130
varying vec2 texture_coordinate;
uniform sampler2D texture;

void main()
{
    vec3 textureColor = texture2D(texture, texture_coordinate).rgb;
    gl_FragColor = vec4(textureColor, 1.0f);
}

Quad render code:

glBegin(GL_QUADS);
        glColor4f(0.0f, 0.0f, 0.7f, 1.0f);
        glVertex2f(position.x, position.y + size.y);
        glVertex2f(position.x + size.x, position.y + size.y);
        glVertex2f(position.x + size.x, position.y);
        glVertex2f(position.x, position.y);
    glEnd();

Thanks in advance.

Answer 1

After a long debugging session with Basaa, we discovered that the problem was that texturing was still enabled. We just had to add:

glDisable(GL_TEXTURE_2D)