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/*=========================================================================
Program: Visualization Toolkit
Module: vtkGPUVolumeRayCastMapper_CompositeFS.glsl
Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
All rights reserved.
See Copyright.txt or http://www.kitware.com/Copyright.htm for details.
This software is distributed WITHOUT ANY WARRANTY; without even
the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
PURPOSE. See the above copyright notice for more information.
=========================================================================*/
// Fragment program part with ray cast and composite method.
#version 110
uniform sampler3D dataSetTexture;
uniform sampler1D opacityTexture;
uniform vec3 lowBounds;
uniform vec3 highBounds;
// Entry position (global scope)
vec3 pos;
// Incremental vector in texture space (global scope)
vec3 rayDir;
float tMax;
// from cropping vs no cropping
vec4 initialColor();
// from 1 vs 4 component shader.
float scalarFromValue(vec4 value);
vec4 colorFromValue(vec4 value);
// from noshade vs shade.
void initShade();
vec4 shade(vec4 value);
void trace(void)
{
vec4 destColor=initialColor();
float remainOpacity=1.0-destColor.a;
bool inside=true;
vec4 color;
vec4 opacity;
initShade();
float t=0.0;
// We NEED two nested while loops. It is trick to work around hardware
// limitation about the maximum number of loops.
while(inside)
{
while(inside)
{
vec4 value=texture3D(dataSetTexture,pos);
float scalar=scalarFromValue(value);
// opacity is the sampled texture value in the 1D opacity texture at
// scalarValue
opacity=texture1D(opacityTexture,scalar);
if(opacity.a>0.0)
{
color=shade(value);
color=color*opacity.a;
destColor=destColor+color*remainOpacity;
remainOpacity=remainOpacity*(1.0-opacity.a);
}
pos=pos+rayDir;
t+=1.0;
inside=t<tMax && all(greaterThanEqual(pos,lowBounds))
&& all(lessThanEqual(pos,highBounds))
&& (remainOpacity>=0.0039); // 1/255=0.0039
}
}
gl_FragColor = destColor;
gl_FragColor.a = 1.0-remainOpacity;
}
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