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Re: how to keep an image object in the window? [message #50292 is a reply to message #50244]

Tue, 26 September 2006 16:24

Karl Schultz
Messages: 341
Registered: October 1999

Senior Member

On Tue, 26 Sep 2006 12:08:49 -0700, Rick Towler wrote:

> Karl Schultz wrote:
>> "In your case this doesn't matter since
>> you're rendering IDLgrVolume objects which force IDL to use the software
>> renderer anyways."
>>
>> IDLgrVolume uses raycasting to generate an intermediate
>> and private IDLgrImage and then renders the IDLgrImage to the device,
>> using either hardware or software rendering, depending on how the device
>> was set up.
>>
>> Raycasting is very slow, and is a software rendering process, but the
>> result may actally be displayed with hardware rendering. So, putting an
>> IDLgrVolume into a scene doesn't cause an automatic switch to the software
>> renderer.
>>
>
> Thanks for clarifying. Makes sense too. After I posted that I thought
> that I was probably assuming too much.
>
> <sigh>
>
> Do you texture a "billboard" with the output of the raycaster?
>
> -Rick

The raycaster outputs an RGBA image, where the A channel has opacity
information. It also outputs a "depth array". The RGBA image is drawn
like any other image via IDLgrImage, which currently uses a texture-mapped
polygon. The depth information is also written to the depth buffer so
that the volume "depth" is communicated to the device in what would
otherwise be a simple 2D image rendering step. This allows you to, for
example, create an isosurface of the volume and draw it in the same view a
the volume itself. The volume rendering, depending on opacity, is then
able to obscure the isosurface where appropriate. iVolume is a good place
to play with this, since iVolume has an operation that will generate the
isosurface and then display it in the same view.

Karl

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[Message index]

		how to keep an image object in the window? By: yy on Sun, 24 September 2006 10:59
		Re: how to keep an image object in the window? By: Karl Schultz on Tue, 26 September 2006 16:24
		Re: how to keep an image object in the window? By: Rick Towler on Tue, 26 September 2006 12:08
		Re: how to keep an image object in the window? By: Karl Schultz on Tue, 26 September 2006 10:42
		Re: how to keep an image object in the window? By: yy on Tue, 26 September 2006 10:32

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