On Wed, 4 Dec 2002, Tino Schwarze wrote:

> On Tue, Dec 03, 2002 at 06:39:16PM -0800, Jonathan Cohen wrote:
> > We are seriously considering ripping out all modes except for
> > 32-bit floating point. This would drastically simplify the internal
> > rendering engine and allow us to optimize it significantly.  Since we
> > don't see any real reasons why high-end paint work could not be done
> > entirely in 32-bit float, this is a reasonable thing.
> I'm just curious: What do you get by using 32-bit _float_? Why not use
> 1.31-Bit Fixed Point? It should have a higher precision than 32-bit
> float - at least, it's precision is steady.

For high dynamic range rendering.

The sun is like a billion times brighter than a candle - and a candle
is a thousand times brighter than the dimmest thing a human eye can

Taking a 'true' rendition of the world needs more dynamic range
than even a 32 bit integer.

However, we don't need to measure the brightness of the sun to
the precision of the dimmest thing we can see.  So we DON'T need
the precision of a 32 bit integer.

Hence a 32 bit float is a more reasonable format.

It's also the format that modern graphics cards are beginning to
support (and will increasingly support in the future).

Steve Baker                      (817)619-2657 (Vox/Vox-Mail)
L3Com/Link Simulation & Training (817)619-2466 (Fax)
Work: [EMAIL PROTECTED]           http://www.link.com
Home: [EMAIL PROTECTED]       http://www.sjbaker.org

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