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/*=========================================================================
Program: Visualization Toolkit
Module: vtkSphericalDirectionEncoder.cxx
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.
=========================================================================*/
#include "vtkSphericalDirectionEncoder.h"
#include "vtkObjectFactory.h"
#include "vtkMath.h"
#include "vtkTransform.h"
vtkStandardNewMacro(vtkSphericalDirectionEncoder);
float vtkSphericalDirectionEncoder::DecodedGradientTable[65536 * 3];
int vtkSphericalDirectionEncoder::DecodedGradientTableInitialized = 0;
// Construct the object. Initialize the index table which will be
// used to map the normal into a patch on the recursively subdivided
// sphere.
vtkSphericalDirectionEncoder::vtkSphericalDirectionEncoder()
{
this->InitializeDecodedGradientTable();
}
// Destruct a vtkSphericalDirectionEncoder - free up any memory used
vtkSphericalDirectionEncoder::~vtkSphericalDirectionEncoder()
{
}
// Encode n into a 2 byte value. The first byte will be theta - the
// rotation angle around the z axis. The second (high order) byte is
// phi - the elevation of the vector. 256 values are used for theta,
// but only 255 values for phi, leaving room for a "zero normal" code
int vtkSphericalDirectionEncoder::GetEncodedDirection( float n[3] )
{
if ( n[0] == 0.0 && n[1] == 0.0 && n[2] == 0.0 )
{
return ( 255 * 256 );
}
float theta, phi;
// Need to handle this separately since some atan2 implementations
// don't handle a zero denominator
if ( n[0] == 0 )
{
theta = ( n[1] > 0 ) ? 90.0 : 270.0 ;
}
else
{
theta = vtkMath::DegreesFromRadians( atan2( n[1], n[0] ) );
theta = ( theta < 0.0 ) ? ( theta + 360.0 ) : theta;
theta = ( theta >= 360.0 ) ? ( theta - 360.0 ) : theta;
}
phi = vtkMath::DegreesFromRadians( asin( n[2] ) );
phi = phi > 90.5 ? ( phi-360 ) : phi;
int lowByte, highByte;
lowByte = static_cast<int>( theta * 255.0 / 359.0 + 0.5 );
highByte = static_cast<int>( ( phi + 90.0 ) * 254.0 / 180.0 + 0.5 );
lowByte = lowByte < 0 ? 0 : lowByte;
lowByte = lowByte > 255 ? 255 : lowByte;
highByte = highByte < 0 ? 0 : highByte;
highByte = highByte > 254 ? 254 : highByte;
return ( lowByte + highByte * 256 );
}
float *vtkSphericalDirectionEncoder::GetDecodedGradient( int value )
{
return &(vtkSphericalDirectionEncoder::DecodedGradientTable[value*3]);
}
// This is the table that maps the encoded gradient back into
// a float triple.
void vtkSphericalDirectionEncoder::InitializeDecodedGradientTable()
{
if ( vtkSphericalDirectionEncoder::DecodedGradientTableInitialized )
{
return;
}
float theta, phi;
int i, j;
vtkTransform *transformPhi = vtkTransform::New();
vtkTransform *transformTheta = vtkTransform::New();
float v1[3] = {1,0,0};
float v2[3], v3[3];
float *ptr = vtkSphericalDirectionEncoder::DecodedGradientTable;
for ( j = 0; j < 256; j++ )
{
phi = -89.5 + j * ( 179.0 / 254.0 );
transformPhi->Identity();
transformPhi->RotateY( -phi );
transformPhi->TransformPoint( v1, v2 );
for ( i = 0; i < 256; i++ )
{
if ( j < 255 )
{
theta = i * (359.0 / 255.0);
transformTheta->Identity();
transformTheta->RotateZ( theta );
transformTheta->TransformPoint( v2, v3 );
}
else
{
v3[0] = 0.0;
v3[1] = 0.0;
v3[2] = 0.0;
}
*(ptr++) = v3[0];
*(ptr++) = v3[1];
*(ptr++) = v3[2];
}
}
transformPhi->Delete();
transformTheta->Delete();
vtkSphericalDirectionEncoder::DecodedGradientTableInitialized = 1;
}
// Print the vtkSphericalDirectionEncoder
void vtkSphericalDirectionEncoder::PrintSelf(ostream& os, vtkIndent indent)
{
this->Superclass::PrintSelf(os,indent);
os << indent << "Number of encoded directions: " <<
this->GetNumberOfEncodedDirections() << endl;
}
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