[vtkusers] VTK 5.6.0 vtkGPUVolumeRayCastMapper very slow?

[Elvis Chen]

greetings,

I've just compiled VTK 5.6.0 and was testing vtkGPUVolumeRayCastMapper using
the GPURenderDemo.cxx.  Using a CT volume available to me (512x512x481,
short), I found the rendering to be VERY slow:  it is non-interactive at
all.  If I use a mouse to change the camera position, I basically have to
wait about 5-8 seconds for the rendering to complete.

I'm using:

Windows-7, 64bit
Intel i7-860 (4 core at 2.80GHz)
4GB RAM
Nvidia GTX260 with 196.21 driver, 896MB of video RAM
Visual Studio Express 2008

VTK 5.6.0 was compiled with all the standard options, except with python
binding (ON).

My questions are:

1) is there a way to display the frame rate to quantify the rendering speed?
2) the CT volume is about 240MB, which should fit inside the video RAM.  Has
anyone else notice the slow speed?  Should I expect
vtkGPUVolumeRayCastmapper to be faster (or slower) than
vtkFixedPointVolumeRayCastMapper?


Once I know how to do 1) I'll write a small program to test the speed
difference between
vtkGPUVolumeRayCastMapper/vtkFixedPointVolumeRaycastMapper.

any insight is very much appreciated,

Elvis
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