Re: [GtkGLExt] Is it possible to use overlays with gtkglextmm?

[Jose Commins <axora axora net>]

   It would depend on how your data is ordered.  Consider a 1000x1000 
(8-bit) texture, that can hold 1,000,000 points.  That's 1Megabyte.   
Ok, x1000 for that for a 3D texture volume and that's 1Gb of texture 
data for 1 billion points :P

   Depending on your data is formatted and such these kinds of figures 
are way more than you need, however, it's set as an example.  A modern 
card, or even a pair or more for parallel computing (see nVidia) can 
handle quite a lot - if you want to see a test of volumetric rendering 
you can download and profile much sample code out there!

   I have to add one thing, as I read this in your last post:

> of the requirements is to have the facility to view large files in full
> detail. Applying transformations globally and moving the points away
> from the origin also cannot work because OpenGL uses single precision
> floating point, which cannot handle the need for having coordinates that
> can express, with precision, values such as 20000.345, so I currently
> place the points around the origin, their coordinates subtracted by
> offsets that change each time. Also, I have been using GTK because the

   No need to use floating point by the way, and you can get round 
single-precision quite easily by multiplying your values by, say, 1000 
before storing them in your vertex array.  There's a lot of headroom in 
there!

Regards,
            Jose.

> -------- Original Message --------
> Subject: 	Re: Is it possible to use overlays with gtkglextmm?
> Date: 	Thu, 11 Feb 2010 17:20:12 +0000
> From: 	Haraldur Tristan Gunnarson <harg pml ac uk>
> To: 	Jose Commins <axora axora net>
>
>
>
> Hi Jose,
>
> Would that work with tens of millions of points in a bottom layer and
> with boxes and lines in a top layer, with the boxes and lines changing
> without having to redraw the stuff on the bottom layer? If so, what
> would the performance be like? Would it involve rasterisation being done
> twice? I also worry that such a large texture might take up a lot of
> additional memory.
>
> Regards,
>
> Haraldur
>
> On 10/02/10 14:15, Jose Commins wrote:
>   
> >       You can try using 3D textures for volumetric rendering, it lends
> > itself to layer-slicing quite well.
> >
> > Regards,
> >          Jose.
> >     
>
>