Shader effect displayed as 1/4 of screen

[kuzulis]

Hi all.

I want to implement a (Dizzy) shader effect, taken from the 'AMD RenderMonkey' utility.
A source code of that shaders are:

== vertex ==

varying vec2 vTexCoord;
void main(void)
{
   // Clean up inaccuracies
   vec2 Position;
   Position.xy = sign(gl_Vertex.xy);
   gl_Position = vec4(Position.xy, 0.0, 1.0);
   vTexCoord = Position.xy;
}

== fragment ==

// Basic idea:
// Rings = sin(radius)
// Spiral = slow offset according to angle, so sin(angle + radius)
// Add time for animation
uniform float exponent;
uniform float speed;
uniform float rings;
uniform float time_0_X;
varying vec2 vTexCoord;

void main(void)
{
   float ang = atan( vTexCoord.y / vTexCoord.x );
   float rad = pow( dot( vTexCoord, vTexCoord ), exponent );
   vec4 value =  vec4( sin( ang + rings * rad + speed * time_0_X ) );
   value = vec4( 0.5, 0.5, 0.5, 0.5 ) * ( vec4( 1.0, 1.0, 1.0, 1.0 ) + value );
   if( vTexCoord.x < 0.0 ) 
   {   
      value = 1.0 - value;
   }
   gl_FragColor = value;
}

I have modified this code to the my QML application with a shader effect item:

ShaderEffect {
        ...
        ...
        blending: false

        vertexShader: "
            uniform highp mat4 qt_Matrix;
            attribute highp vec4 qt_Vertex;
            attribute highp vec2 qt_MultiTexCoord0;
            varying highp vec2 qt_TexCoord0;
            void main() {
                qt_TexCoord0 = qt_MultiTexCoord0;
                gl_Position = qt_Matrix * qt_Vertex;
            }"

        fragmentShader: "
            // Basic idea:
            // Rings = sin(radius)
            // Spiral = slow offset according to angle, so sin(angle + radius)
            // Add time for animation

            uniform float exponent;
            uniform float speed;
            uniform float rings;
            uniform float time_0_X;
            uniform highp mat4 qt_Matrix;
            varying vec2 qt_TexCoord0;

            void main(void)
            {
               float ang = atan( qt_TexCoord0.y / qt_TexCoord0.x );
               float rad = pow( dot( qt_TexCoord0, qt_TexCoord0 ), exponent );
               vec4 value =  vec4( sin( ang + rings * rad + speed * time_0_X ) );
               value = vec4( 0.5, 0.5, 0.5, 0.5 ) * ( vec4( 1.0, 1.0, 1.0, 1.0 ) + value );
               if( qt_TexCoord0.x < 0.0 )
               {
                  value = 1.0 - value;
               }
               gl_FragColor = value;
            }
        "
        ...
        ...
}

But, in my case, the QML's effect show an 1/4 of original dizzy. I suspect that a reason can be in a different coordinates mesh in qt (where are 0.0 ... 1.0) and in OpenGL (where are -1.0 ... 1.0). But I'm not an expert, and I don't know how to fix my shaders according to original dizzy example.

Could someone help me?

Original

My

[kuzulis]

Ahh... need just to add an offset (-0.5, -0.5) to the vertex shader:

qt_TexCoord0 = qt_MultiTexCoord0 + vec2(-0.5, -0.5);