drr-exponential.frag

#version 330
 
/*
 *  Copyright (C) 2010 - 2016 Leonid Kostrykin
 *
 *  Chair of Medical Engineering (mediTEC)
 *  RWTH Aachen University
 *  Pauwelsstr. 20
 *  52074 Aachen
 *  Germany
 * 
 * 
 *  Copyright (C) 2021 - 2025 Leonid Kostrykin
 * 
 */
 
uniform sampler2D integralMap;
uniform float     baseIntensity;
uniform int       renderInverse;
 
in vec2 textureCoordinates;
 
layout( location = 0 ) out vec4 _gl_FragColor;
 
 
// ----------------------------------------------------------------------------------
// Fragment Procedure
// ----------------------------------------------------------------------------------
 
void main()
{
    float integral = texture( integralMap, textureCoordinates ).r;
    float result   = clamp( baseIntensity * exp( -integral ), 0, 1 );
 
    vec3 color = ( 1 - renderInverse ) * vec3( 1, 1, 1 );
 
    _gl_FragColor = vec4( color, 1 - result );
}