I think TransferFunction needs to call _image->dirty() in two places in
response to an assign() of new transfer map values.
Here's an updated file, which seems to work here.
Paul
-------- Original Message --------
Subject: Re: [osg-users] osgVolume ready for testing
Date: Fri, 30 Jan 2009 13:04:08 +0000
From: Robert Osfield <[email protected]>
To: Paul Melis <[email protected]>, OpenSceneGraph Users
<[email protected]>
References:
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<[email protected]>
Hi Paul,
On Fri, Jan 30, 2009 at 12:55 PM, Paul Melis <[email protected]> wrote:
BTW, is there currently support in osgVolume for interactively manipulating
a transfer function?
I haven't tried it yet, but it should work automatically.
osg::TransferFunction1D holds an osg::Image that it should update and
dirty, and this osg::Image is attached to a convention texture which
should in theory just update when the image is updated.
I noticed the call to osgVolume::applyTransferFunction() in the osgvolume
example and that one kind of feels like it does processing on the image
data. Is that correct?
You can apply the transfer function directly to the image, but with
GPU based shaders I've found it best to do all the compute of the
transfer function on the GPU, it's faster and produces high quality
results and... you can update the transfer function dynamically.
Robert.
/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2006 Robert Osfield
*
* This library is open source and may be redistributed and/or modified under
* the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or
* (at your option) any later version. The full license is in LICENSE file
* included with this distribution, and on the openscenegraph.org website.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* OpenSceneGraph Public License for more details.
*/
#include <osg/TransferFunction>
#include <osg/Notify>
#include <osg/io_utils>
using namespace osg;
///////////////////////////////////////////////////////////////////////
//
// TransferFunction base class
//
TransferFunction::TransferFunction()
{
}
TransferFunction::~TransferFunction()
{
}
///////////////////////////////////////////////////////////////////////
//
// TransferFunction1D class
//
TransferFunction1D::TransferFunction1D()
{
_minimum = 0.0;
_maximum = 1.0;
}
void TransferFunction1D::setInputRange(float minimum, float maximum)
{
_minimum = minimum;
_maximum = maximum;
}
void TransferFunction1D::allocate(unsigned int numX)
{
_colors.resize(numX);
_image = new osg::Image;
_image->setImage(numX,1,1,GL_RGBA, GL_RGBA, GL_FLOAT, (unsigned char*)&_colors[0], osg::Image::NO_DELETE);
}
void TransferFunction1D::clear(const osg::Vec4& color)
{
for(Colors::iterator itr = _colors.begin();
itr != _colors.end();
++itr)
{
*itr = color;
}
}
void TransferFunction1D::assign(const ValueMap& vcm, bool updateMinMaxRange)
{
if (vcm.empty()) return;
if (updateMinMaxRange)
{
_minimum = vcm.begin()->first;
_maximum = vcm.rbegin()->first;
}
if (_colors.empty()) allocate(1024);
float multiplier = float(_colors.size()-1)/(_maximum - _minimum);
if (vcm.size()==1)
{
osg::Vec4 color = vcm.begin()->second;
if (_minimum == _maximum)
{
clear(color);
}
else
{
float iPos = (vcm.begin()->first - _minimum)*multiplier;
if (iPos>=0.0f || iPos<float(_colors.size()))
{
float iFloor = floorf(iPos);
unsigned int i = (unsigned int)(iFloor);
_colors[i] = color;
}
}
_image->dirty();
return;
}
ValueMap::const_iterator lower_itr = vcm.begin();
ValueMap::const_iterator upper_itr = lower_itr;
++upper_itr;
for(;
upper_itr != vcm.end();
++upper_itr)
{
float lower_v = lower_itr->first;
const osg::Vec4& lower_c = lower_itr->second;
float upper_v = upper_itr->first;
const osg::Vec4& upper_c = upper_itr->second;
float lower_iPos = (lower_v - _minimum)*multiplier;
float upper_iPos = (upper_v - _minimum)*multiplier;
float start_iPos = ceilf(lower_iPos);
if (start_iPos<0.0f) start_iPos=0.0f;
if (start_iPos>float(_colors.size()-1)) break;
float end_iPos = floorf(upper_iPos);
if (end_iPos<0.0f) continue;
if (end_iPos>float(_colors.size()-1)) end_iPos=_colors.size()-1;
Vec4 delta_c = (upper_c-lower_c)/(upper_iPos-lower_iPos);
unsigned int i=static_cast<unsigned int>(start_iPos);
for(float iPos=start_iPos;
iPos<=end_iPos;
++iPos, ++i)
{
_colors[i] = lower_c + delta_c*(iPos-lower_v);
}
lower_itr = upper_itr;
}
_image->dirty();
}
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