#ifdef GL_ES

precision mediump float;

#endif

uniform mat3 worldToOutput;

uniform vec4 outputRect;

varying vec4 inputRect[1];

varying mat3 worldToInput[1];

uniform float radius;

float det(mat3 m) { return m[0][0] * m[1][1] - m[0][1] * m[1][0]; }

void main( void )

{

  float rad  = radius * sqrt(abs(det(worldToOutput)));

  worldToInput[0] = worldToOutput;                    // Let the input and output references

                                                      // be the same

  inputRect[0] = vec4(

    outputRect.x - rad,

    outputRect.y - rad,

    outputRect.z + rad,

    outputRect.w + rad);

  gl_Position = vec4(0.0);                            // Does not link without

}