//=============================================================================
//
// Project:   SharpImage
// Module:    shader-v.frag
// Language:  OpenGL Shading Language (GLSL)
// Author:    Dan Mueller
// Date:      $Date: 2007-07-06 10:57:00 +1000 (Fri, 06 Jul 2007) $
// Revision:  $Revision: 2 $
//
// Copyright (c) Queensland University of Technology (QUT) 2007.
// All rights reserved.
//
// This software is distributed WITHOUT ANY WARRANTY; without even
// the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
// PURPOSE.  See the copyright notices for more information.
//
//=============================================================================

uniform sampler3D sam3Tex0;  // Sampler for transfer function
uniform sampler3D sam3Tex1;  // Sampler for value image
varying vec3 pos3Tex1;       // Current coord of value image

void main()
{
    // Interpolate images
    float value = texture3D( sam3Tex1, pos3Tex1 ).a;

    // Interpolate transfer function
    vec3 pos3Tf = vec3( value, 0.0, 0.0 );
    vec4 val4Tf = texture3D( sam3Tex0, pos3Tf );
    
    // Discard if no contribution
    if (val4Tf.a <= 0.0) discard;

    // Set color
    gl_FragColor = val4Tf;
}