vtkPolyData 示例代碼

 

本文主要介紹使用使用一系列的點生成各種 PolyData 的過程。

我們首先生成螺旋曲線， 這個比較簡單。 使用一些簡單的數據知識就可以辦到：

/********************************************
 * 描述：
 *    構建形成線條的所有點集。
 * 參數列表：
 *  count - 線條所在坐標三個維度的分辨率。
 * 返回值：
 *    線條的點集。
 *******************************************/
std::vector < vtkPoint >  BuildPoints ( int count )
{
    std::vector < vtkPoint > points;

    for ( int y = 0; y < count; y++ )
    {        
        vtkPoint point;
        point.x = radians * cos ( y / vtkMath::Pi() );
        point.y = y;
        point.z = radians * sin ( y / vtkMath::Pi() );
        point.radians = 3; 
        points.push_back ( point );        
    }

    return points;
}

 

有了點之后，我們把這些點連接成線。

/********************************************
 * 描述：將點連成線
 * 參數列表：
 *    points - 點集.
 * 返回值：
 *    用 vtkPolyData 表示的線條。
 *******************************************/
vtkPolyData * BuildLines ( std::vector < vtkPoint > & points )
{
    vtkNew <vtkPoints> polydataPoints;
    vtkNew < vtkCellArray > cells;

    int count = points.size();
    for ( int i=0; i<count; i++ )
    {
        polydataPoints->InsertNextPoint ( points[i].x, points[i].y, points[i].z );
    }

    for ( int i=0; i<count-1; i++ )
    {
        vtkIdType pts[2] = { i, i+1 };
        cells->InsertNextCell ( 2, pts );
    }

    vtkPolyData * polyData = vtkPolyData::New ();
    polyData->SetPoints ( polydataPoints );
    polyData->SetLines ( cells );

    return polyData;
}

然后我們就可以把這個線顯示出來：如圖

 

 

 之后我們繼續以每個點為圓心作圓。

vtkPolyData * BuildCircles ( std::vector < vtkPoint > & points, int resolution )
{
    std::vector < vtkPoint > circlePoints = BuildCirclePoints ( points, resolution );
    
    vtkNew < vtkAppendPolyData > append;
    int count = circlePoints.size();
    
    for ( int i=0; i<count; i+=resolution )
    {
        vtkNew < vtkPoints > vPoints;
        vtkNew < vtkCellArray > cells;
        
        for ( int j=0; j<resolution; j++ )
        {
            int idx = i+j;
            vPoints->InsertNextPoint ( circlePoints[idx].x, circlePoints[idx].y, circlePoints[idx].z );
        }

        for ( int j=0; j<resolution; j++ )
        {
            int n = j+1;
            if ( n >= resolution )
                n = 0;

            vtkIdType pts[2] = {j, n};
            cells->InsertNextCell ( 2, pts );
        }

        vtkNew < vtkPolyData > polyData;
        polyData->SetPoints ( vPoints );
        polyData->SetLines ( cells );
        append->AddInputData ( polyData );
    }

    //
    append->Update ();
    vtkPolyData * retPolyData = append->GetOutput ();
    retPolyData->Register ( NULL );

    //
    return retPolyData;
}

將它返回的 retPolyData 顯示出來就是下面的樣子。

 

 

 

 最后，我們只需連接上下兩個圓的點，形成面片，就可以生成三維表面了。

/********************************************
* 描述： 構建表面。
*    參數列表：
*        points - 點集，每一個點都是一個圓的圓心。
*        resolution - 圓是由一系列的線段構成， resolution 指定線段數量。
* 返回值：
*    返回所有圓構成的表面.
*******************************************/
vtkPolyData * BuildSurface ( std::vector < vtkPoint > & points, int resolution )
{
    std::vector < vtkPoint > circlePoints = BuildCirclePoints ( points, resolution );

    vtkNew < vtkAppendPolyData > append;
    int count = circlePoints.size() - resolution;

    for ( int i=0; i<count; i+=resolution )
    {
        for ( int j=0; j<resolution; j++ )
        {
            vtkNew < vtkPoints > vPoints;
            vtkNew < vtkCellArray > cells;

            bool bflag = j == ( resolution-1 );

            int idx = j+i;
            int lt = idx;
            int rt = idx + 1;
            int rd = rt + resolution;
            int ld = lt + resolution;

            if ( bflag ) 
            {
                rt = i;
                rd = i + resolution;
            }


            vPoints->InsertNextPoint ( circlePoints[lt].x, circlePoints[lt].y, circlePoints[lt].z );
            vPoints->InsertNextPoint ( circlePoints[rt].x, circlePoints[rt].y, circlePoints[rt].z );
            vPoints->InsertNextPoint ( circlePoints[rd].x, circlePoints[rd].y, circlePoints[rd].z);
            vPoints->InsertNextPoint ( circlePoints[ld].x, circlePoints[ld].y, circlePoints[ld].z);

            //
            vtkNew < vtkQuad > quad;
            for ( int c=0; c<4; c++ )
            {
                quad->GetPointIds()->SetId ( c, c );            
            }
            cells->InsertNextCell ( quad );

            //
            vtkNew < vtkPolyData > polyData;
            polyData->SetPoints ( vPoints );
            polyData->SetPolys ( cells );
            append->AddInputData ( polyData );
        }        
    }

    //
    append->Update ();
    vtkPolyData * retPolyData = append->GetOutput ();
    retPolyData->Register ( NULL );

    //
    return retPolyData;
}

把這里返回的 PolyData 顯示出來就是下面的樣子：