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//=========================================================================
//
// Program: Visualization Toolkit
// Module: vtkLineIntegralConvolution2D_LIC0.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.
//
//=========================================================================
/**
This shader initializes the convolution for the LIC computation.
*/
// The following line handles system declarations such as
// default precisions, or defining precisions to null
//VTK::System::Dec
// the output of this shader
//VTK::Output::Dec
uniform sampler2D texMaskVectors;
uniform sampler2D texNoise;
uniform sampler2D texLIC;
uniform int uStepNo; // in step 0 initialize lic and seeds, else just seeds
uniform int uPassNo; // in pass 1 hpf of pass 0 is convolved.
uniform float uMaskThreshold; // if |V| < uMaskThreshold render transparent
uniform vec2 uNoiseBoundsPt1; // tc of upper right pt of noise texture
varying vec2 tcoordVC;
// convert from vector coordinate space to noise coordinate space.
// the noise texture is tiled across the *whole* domain
vec2 VectorTCToNoiseTC(vec2 vectc)
{
return vectc/uNoiseBoundsPt1;
}
// get the texture coordidnate to lookup noise value. this
// depends on the pass number.
vec2 getNoiseTC(vec2 vectc)
{
// in pass 1 : convert from vector tc to noise tc
// in pass 2 : use vector tc
if (uPassNo == 0)
{
return VectorTCToNoiseTC(vectc);
}
else
{
return vectc;
}
}
// look up noise value at the given location. The location
// is supplied in vector texture coordinates, hence the
// need to convert to noise texture coordinates.
float getNoise(vec2 vectc)
{
return texture2D(texNoise, getNoiseTC(vectc)).r;
}
void main(void)
{
vec2 vectc = tcoordVC.st;
// lic => (convolution, mask, 0, step count)
if (uStepNo == 0)
{
float maskCriteria = length(texture2D(texMaskVectors, vectc).xyz);
float maskFlag;
if (maskCriteria <= uMaskThreshold)
{
maskFlag = 1.0;
}
else
{
maskFlag = 0.0;
}
float noise = getNoise(vectc);
gl_FragData[0] = vec4(noise, maskFlag, 0.0, 1.0);
}
else
{
gl_FragData[0] = texture2D(texLIC, vectc);
}
// initial seed
gl_FragData[1] = vec4(vectc, 0.0, 1.0);
}
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