title: Binding a zero texture in OpenGL
body: <p>In my program I use 2 textures: t0 and t1. t1 is additional, needed only in some cases:</p>
  
  <pre><code>.....
  glActiveTexture ( GL_TEXTURE1 );
  if ( mDisplayMode == EDM_DEFAULT ){
      glBindTexture( GL_TEXTURE_2D, 0 ); // In this case I don't need t1
  }else{
      glBindTexture( GL_TEXTURE_2D, mglDegreeTexture ); // In this case t1 will overlap t0
  }
  shader-&gt;setUniformValue( "textureId1", 1 );
  </code></pre>
  
  <p>Shader for drawing:</p>
  
  <pre><code>.....
  vec4 c1 = texture( textureId0, uv );
  vec4 c2 = texture( textureId1, gridUV );
  float a = c2.a;
  gl_FragColor = ( 1.0 - a )*c1 + a*c2;
  </code></pre>
  
  <p>It's works fine: second texture overlap first when needed. Assuming that using glBindTexture( .. , 0 ) return zero texture (0,0,0,0), but after updating NVidia drivers to 314.07, my code procude black screen, like glBindTexture( .. , 0 ) return (0,0,0,1) texture.</p>
  
  <p>I perform some test: 
  With shader</p>
  
  <pre><code>....
  vec4 c1 = texture( textureId0, uv );
  vec4 c2 = texture( textureId1, gridUV );
  float a = c2.a;
  if (a == 1){
      gl_FragColor = vec4(1,0,0,0);
      return;
  }
  if ( a == 0){
      gl_FragColor = vec4(0,1,0,0);
      return;
  }
  gl_FragColor = ( 1.0 - a )*c1 + a*c2;
  </code></pre>
  
  <p>I get green screen on old driver (296, 306), and red on a new one. I tested it on 2 computers with Win 7 (GeForce 210) and win XP (GTX 260).</p>
  
  <p>So my question is: It is correct to use glBindTexture with 0 as second parameter, and how I can achieve same result ( 0000 texture ) with a new driver?</p>