On Wed, Nov 4, 2009 at 7:50 AM, Tim Moore <timo...@redhat.com> wrote:
> 32-bit indices are slower in OpenGL than 16-bit, so it's not desirable to
> switch to use longer indices everywhere, if at all. It would be
> better to split the scenery up into chunks that can be addressed using 16
> bits.
> I haven't looked closely at this, but I think such a .btg file would be
> binary compatible with older versions of FlightGear.
>
FlightGear uses a fixed tiling scheme. Things to consider would be the tile
loading and caching scheme which makes assumptions about tile sizes and
layout to maintain the local scenery cache. Another thing to consider is
the boundaries between tiles. It's hard to put two or more smaller tiles up
next to a larger tile without introducing a chance of pixel wide cracks ...
unless the larger tile is generated with a vertex layout that matches the
adjoining smaller tiles.
But while we're talking about .btg file changes, I'd love to get rid of
> triangle strips and fans and generate optimized triangle elements at
> scenery
> generation time, rather than doing it at load time...
>
Two thoughts ... first what you propose is more of a "terragear" change,
probably with some mimimal extension to the .btg format. 2nd, the way we
define tiles is that we have a top level .stg file that defines what is
included in that tile. The .btg file is just our own custom 3d file
format. There's no reason we couldn't define the base terrain as an
openflight or .3ds or .ac model and load it in from the .stg file. (If we
were designing this from scratch today, the .stg file would probably be an
xml file that supported all the same animations, selections, sub-model
references, and grouping capability as any other model xml file ... hmmm
....)
Curt.
--
Curtis Olson: http://baron.flightgear.org/~curt/
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