[vtkusers] Performance of 2DMapping

[John Biddiscombe]

When you use ImageActor (3D) you are creating a Texture and the hardware does all the work of displaying it.
When you use an ImageMapper, glDrawPixels (or whatever it's called) does all the work, which is often slower. The main reason for using the 2D functions is that the image is never resampled if it can't fit into texture memory (or interpolated etc etc).

JB

RPD : A drag drop front end for vtk 
www.skippingmouse.co.uk

> -----Original Message-----
> From: Hämäläinen Janne [mailto:Janne.Hamalainen at hus.fi]
> Sent: 17 July 2003 15:33
> To: 'vtkusers at vtk.org'
> Subject: [vtkusers] Performance of 2DMapping
> 
> 
> Hi,
> 
> I've used combination of vtkImageMapper and vtkActor2D to 
> present 2D images.
> Recently I tried presenting the same images using 
> vtkImageActor, i.e., in
> effect putting them to 3D. I noticed that all the operations, e.g.,
> windowing and leveling of the gray level and swapping regions 
> between images
> (as with vtkImageStencil) work much faster. In other words, 
> the display
> updating is much smoother. Is my observation correct, and is 
> this in general
> the case (or does it depend, e.g., on the used graphics 
> card)? My first
> hunch would be that the 3D mode uses hardware acceleration 
> and in 2D the
> processing would be done in software. Has anyone idea how things are
> working, and is there any reason to use 2D mapping?
> 
> Thanks, 
> 
> Janne
> 
> 
> 
> --
> Janne Hämäläinen
> Research Assistant
> Helsinki University Central Hospital 
> X-ray Department				
> 
> email   janne.hamalainen at hus.fi
> 
> 
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