[vtkusers] Newbie question about VTK speed

[Hughes, Mike]

I've just started using VTK to do image processing.  I wrote the program
below (Vol-r5) to test the frame rate for writing different images to the
screen of my computer (Dual dual-core Xeons with and VCQFX1500-PCIE-PB Nvidia
1500 video adapter running Ubuntu linux with working OpenGL drivers
installed).

When I run the program I get the following output:
	$ ./Vol-r5
	dt= 2.57 for: 180 frames
Where dt is the execution time to compute and display 180 frames.

This seems to be astoundingly slow for a machine with working OpenGL drivers
installed.  I've explored the VTK class hierarchy and it seems that if OpenGL
is available it should be automatically used.  I hope that I'm mistaken on
this.

Is there a way to display frames at a higher rate?  I would ultmately like to
display 512x512 images (which takes about 9 sec with the program below).

Vol-r5.cpp listing....

#include "vtkImageWriter.h"
#include "vtkImageReader.h"
#include "vtkPointData.h"
#include "vtkRenderer.h"

//#include "vtkRenderWindow.h"
//#include <vtkXOpenGLRenderWindow.h>

#include "vtkImageViewer.h"
#include "vtkRenderWindowInteractor.h"
#include "vtkStructuredPoints.h"
#include "vtkFloatArray.h"
#include "vtkContourFilter.h"
#include "vtkPolyDataMapper.h"
#include "vtkActor.h"
#include "vtkImageCast.h"

#include <time.h>

const float Pi=3.14159;
const int NumberOfFrames=180;

int main ()
{

	float sp, z, y, x, s, dx,dy,scale;
	int i, j, k, ii, kOffset, jOffset, offset,h;
	int xSize=255;
	int ySize=255;
	int zSize=0;
	clock_t start, stop;
	dx=1.0/((double)xSize);
	dy=1.0/((double)ySize);

	vtkImageData *image = vtkImageData::New();
	image->SetDimensions(xSize+1,ySize+1,zSize+1);
	image->SetScalarTypeToFloat();
	image->AllocateScalars();

	float *ptr = static_cast<float*>(image->GetScalarPointer());
	float *startptr;
	startptr = ptr;

	vtkImageViewer *viewer = vtkImageViewer::New();
	viewer->SetInput(image);
	viewer->SetColorWindow(20.0);
	viewer->SetColorLevel(0.0);
	start=clock();
	for(scale=1.0,k=0;k<NumberOfFrames;k++,scale+=0.1)
	{
		ptr=startptr;
		for(x=0.0,i=0;i<xSize+1;i++,x+=dx)
			for(y=0.0,j=0;j<ySize+1;j++,y+=dy)
				*ptr++ = scale*sin(8.0*Pi*x)*sin(8.0*Pi*y);
		viewer->Render();
	}
	stop=clock();
	cout << " dt= " << ((double)(stop-start))/((double)CLOCKS_PER_SEC) <<
" for: " << NumberOfFrames << " frames" << endl;

	viewer->Delete();
	image->Delete();
	// Clean up
	return 1;
}