From: Dave Akers (dla@engr.sgi.com)
Date: 04/21/2000 11:33:52
Hi Mark,
Sean's comments on texture distortion were right on the mark -
unfortunately on IMPACT your only option here is to use orthographic
projections to avoid texture distortions for non-viewport aligned 3-D
texture slicing.
To clarify, the available visuals on Octane depend on the number of
rasterization engines (RE's) you have installed. To find out what you've
got, use the "gfxinfo" command. As I mentioned in a previous post, you're
most likely running on an Octane SI with only one RE, which doesn't give
you the best-looking visuals at 1280x1024.. If you want better visuals,
there are options for upgrading (talk to your sales rep.)
As for texture subloading, we've looked into this in the past on IMPACT
and there are severe restrictions on the dimensions of the subload.
Because of these restrictions, you wouldn't want to use texture subloading
on IMPACT to do voxel-editing. Marking each affected brick as
"dirty" and causing a redownload is the best approach in this case. (This
logic is factored into the voxel modification routines included with
version 1.2.)
Dave
On Wed, 19 Apr 2000, Mark Davey wrote:
> Hello.
> I have been working with an Octane over the past couple of months and I
> have a number of problems with respect to the use of this machine with
> Volumizer, although I suspect that none of them are due explicitly to
> Volumizer itself but to the architecture of the machine.
>
> Firstly,
> When using Volumizer to produce a Multi-Planar reformatting of the
> data, where the plane is kept stationary with respect to the data,
> considerable distortion of the texture can be seen as the data is
> rotated. Has anyone else seen this? Is it an Octane problem? This also
> appears to make 'fly-throughs' behave very strangely indeed as the data
> set gently morphs as you pass through the anatomy!
>
> As I have previously mention I was having trouble using glFog at the
> same time as colour lookup tables. As pointed out, this is mentioned in
> the man pages for lookup tables. Does anyone know if the new Octane
> graphics card will have this problem?
>
> I have tried to use
>
> voAppearanceActions::textureSubload(...);
>
> on an Octane only to be told that this command is not supported on the
> Octane... Is this a fundamental problem with the Octane or is it
> Volumizer at fault here?
> This means I cannot do interactive editing of the volume.
>
> Although I have 'solved' the dithering problems encountered when
> displaying textured graphics on the Octane by reducing the screen
> resolution to 1024x768_76 this strikes me as being a poor compromise as
> PC's can do better than this at a small fraction of the cost. Surely a
> standard Octane should be able to display adequate graphics as a
> standard resolution of 1280x1024.
>
> Have I got a sub-standard machine here?
> If not then the pratical uses for Volumizer (and probably any other
> volume-slicing-based volume rendering API) seems limited on the Octane
> (especially
> considering the goemetric distortions)
>
> What would be the platform of choice for Volumizer?
> What is required to get around the above problems? Do I have to use an
> Onyx???
>
> Regards
> Mark....
>
>
> --
> From: Mark Davey
> Dept. of Medical Physics, UCL.
>
> TEL: +44 (0)171 915 1673.
> FAX: +44 (0)171 837 9279.
>
> Institute of Laryngology and Otology,
> 330 Gray's Inn Road,
> London.
> WC1X 8GE.
>
>
>
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