Visualization for isosurface

You modify the program of "Creating structured volume data".

 

1.　Make a working directory

First please create a working directory (e.g., IsoSurface) and move in this directory.

# mkdir  IsoSurface

# cd IsoSurface

 

2.　Programming

You copy from "Creating structured volume data":

# cp ../CreateField/main.cpp  .

and delete under the "file export".

For example:

#include <kvs/Vector3>

#include <kvs/StructuredVolumeObject>

#include <kvs/StructuredVolumeExporter>

#include <kvs/AVSField>

inline float func( float x, float y, float z) {

    return ( 3.0 - x*x - y*y - 4.0*z*z );

}

 

int main( int argc, char** argv )

{

    // resolution of voxel grid

    kvs::UInt32 gridNum = 64;

    const kvs::Vector3ui resol(gridNum, gridNum, gridNum);

    

    kvs::ValueArray<float> data( gridNum * gridNum * gridNum );

 

    float* pdata = data.pointer<float>();

 

    float min = -2.0, max = 2.0;

    float dt = (float)(max - min)/(float)(gridNum-1);

 

    kvs::UInt64 index = 0;

    for(int i=0; i< 64; i++) {

        for(int j = 0; j<64; j++) {

            for(int k=0; k<64; k++) {

                float x = (float)min + (float)k*dt;

                float y = (float)min + (float)j*dt;

                float z = (float)min + (float)i*dt;

                // Ealuate function

                pdata[ index++ ] = func(x, y, z) ;

            }

        }

    }

 

    // Create the instance

    kvs::StructuredVolumeObject *volume = new kvs::StructuredVolumeObject ( );

    // Store the data

    volume->setGridType( kvs::StructuredVolumeObject::Uniform );

    volume->setResolution( resol );

    volume->setVeclen( veclen );

    volume->setValues( data );

 

3.　Maxmum and Minimun value of field data

You can check whether the kvs::StructuredVolumeObject has the minimum and maximum values of a field data or not by using the member function:

If the object does not have the minimum and maximum values, you calculate these value by using the member function:

 

// Calculate min/max values

if ( !volume->hasMinMaxValues() )

    volume->updateMinMaxValues(); 

 

4.　Input isovalue from Standard input

In this program, you input the isovalue from standard input and check whether the input value is in the data range.

// Input isovalue

double input_iso, iso;

double value_min = (double)volume->minValue( )       // mimimun

double value_max = (double>)volume->maxValue( );       // maxmum

 

std::cout << "Input Isolevel [ " << value_min << " - " << value_max << "] : ";

 

// from standart input

std::cin >> input_iso;

 

if    ( input_iso < value_min ) iso = value_min;

else if( input_iso > value_max ) iso = value_max;

else    iso = input_iso;

 

5.　Create the Isosurface

In KVS, there is kvs::Isosurface class that creates the isosurface by using Marching cubes method and transfers to the type of kvs::PolygonObject.

The constructor of kvs::Isosurface has following input parameters:

And then, you check whether the polygon object can be created or not and remove unnecessary volume data.

For example,

kvs::PolygonObject* object =

        new kvs::Isosurface( volume,

               iso,

               kvs::PolygonObject::VertexNormal );    

 

// Check: create the polygon data

if ( !object )

{

    kvsMessageError( "Cannot create a polygon object." );

    delete volume;

    return( false );

}

// remove volume data

delete volume;

 

6.　Drawing

For visualization, we should instantiate classes kvs::glut::Application and kvs::glut::Screen and resiter the viusalized objects to the screen．

// Create and set Screen class

kvs::glut::Screen screen( &app );

screen.registerObject( object );

screen.setGeometry( 0, 0, 512, 512 );

screen.setTitle( "Isosurface");

screen.show();

// Event loop

return( app.run() );

 

7.　Header file

You have to include the header file for following class:

Therefore, you include :

#include <kvs/PolygonObject>

#include <kvs/Isosurface>

#include <kvs/glut/Application>

#include <kvs/glut/Screen>

 

8.　Sample program

Sample program: Isosurface.tgz

 

9.　Compile and execute

Let's try to compile and execute above program.

When compiling a KVS program, it is easy to use the automatic Makefile-generation tool kvsmake supplied by KVS.

# kvsmake -G　　　　　　　　　　<-- Create Makefile

# kvsmake　　　　　　　　　　　　<-- Compile

And then, this program requires the isovalue, you input the isovale.

Following example inputs the isovallue = 0.0.

# ./Isosurface　　　　　　　　　　　　　　

Input Isolevel [ -21 　-　2.99395] :　0.0

 

You can show the isosurface same as kvsview.

Isosurface

　

Last Updated at Nov. 1, 2015　

 

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