There's many ways to slice an orange :P
First of all, all one needs to do is scan through the coordinates
and check for min/max ranges. Because you will be gathering data from a
finite dataset (i.e. one wouldn't expect to use numbers of the
10^1000000 range for example!) you can then act on the given range as
appropriate.
32-bit floats can reliably represent numbers in the integer range of
1^24, so if the data doesn't fit into it, you can use several methods.
Data partitioning is one of them. You can stuff your figures into
32-bit integers, or even 64-bit integers (post multiplied) and just send
the lower 16 or 32 bits to the vertex array according to the viewing
range. It's free range-clipping.
Also one can partition data into 8 volumes, each with their own
coordinate system (with a full dynamic range each of, say, 32 bits)
which is represented on-screen by offset rendering.
Regards,
Jose.
-------- Original Message --------
Subject: Re: [GtkGLExt] Is it possible to use overlays with
gtkglextmm?
From: John Darrington <[email protected]>
Date: Mon, February 15, 2010 7:04 am
To: Jose Commins <[email protected]>
Cc: [email protected], Haraldur Tristan Gunnarson
<[email protected]>
On Fri, Feb 12, 2010 at 05:42:13PM +0000, Jose Commins wrote:
>>> 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!
>>
>
>But the tricky thing is to predict exactly what value to multiply by.
It's
>a non-trivial problem, which whole PhD theses have investigated.
There's
>even a website dedicated to the problem http://www.floatingorigin.com
>
>J'
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