RE: [Algorithms] Massive spaces

[Tom F. <to...@mu...>]

(1) Not as long as your partitions in dvMinZ, dvMaxZ don't overlap, though
that is another way of getting even more precision. But it chews fillrate.
It's not usually necessary.

Tom Forsyth - Muckyfoot bloke.
Whizzing and pasting and pooting through the day.

> -----Original Message-----
> From: Sam Kuhn [mailto:sa...@ip...]
> Sent: 21 August 2000 13:28
> To: gda...@li...
> Subject: Re: [Algorithms] Massive spaces
> 
> 
> Thanks for the info tom, exactly what I wanted to hear. A couple of
> questions:
> 
> 1) Interesting.. do you have to clear the zbuffer when rendering each
> partition?
> 
> 2) Yeah, but if you nail all distant objects to the back clip 
> plane, they
> have the same z and consequently the same parallax. dont 
> they? I guess I
> could treat the back of the view volume as the back of the 
> galaxy, and nail
> the objects into the view volume at their relevant scaled 
> positions. That
> should work.
> 
> 3) Your dead right dude, I tried this yesterday after I sent 
> the mail...
> works very nicely! ;)
> 
> Cheers,
> 
> Sam.
> 
> 
> -----Original Message-----
> From: Tom Forsyth <to...@mu...>
> To: gda...@li...
> <gda...@li...>
> Date: 21 August 2000 2:59 AM
> Subject: RE: [Algorithms] Massive spaces
> 
> 
> >(1) Partition your Z buffer. In D3D this is done using the dvMinZ and
> dvMaxZ
> >values in the viewport. There is a pretty direct equivalent 
> in OpenGL - I
> >forget what it's called. Then you can even out your precision quite
> happily.
> >
> >(2) They're planets. Big spherical things. And they don't (usually -
> depends
> >what sort of game you are doing I guess :-) actually 
> intersect in space.
> >Possibly nothing in the universe is easier to sort from back 
> to front and
> >draw that way. So you can nail them to the far clip plane, 
> set your Z test
> >to LESSTHAN, and there you go.
> >
> >(3) Move your near clip plane according to the nearest 
> object. So if you
> are
> >on a planet's surface, the near clip plane is quite close. If you are
> >zooming about in space, it's millions of miles away.
> >
> >By using all these three, you can get huge spaces done pretty easily.
> >
> >If the archives are working, this has been discussed a fair number of
> times.
> >
> >Tom Forsyth - Muckyfoot bloke.
> >Whizzing and pasting and pooting through the day.
> >-----Original Message-----
> >From: Sam Kuhn [mailto:sa...@ip...]
> >Sent: 21 August 2000 02:33
> >To: gda...@li...
> >Subject: [Algorithms] Massive spaces
> >
> >
> >Hey,
> >
> >I've got a little mind game for you lot.
> >
> >Say you needed to render an entire solar system, in which 
> you can zoom down
> >to a planet surface and see detail of about 1/100000 meter, 
> or shoot over
> to
> >the sun and see the same sort of detail. There are a couple 
> of immediate
> >problems:
> >
> >You would need need an enormous view volume (what say 20 
> lightyears big)
> >which gives an appauling zbuffer resolution.
> >So whats are you to do? Render the distant objects closer than they
> actually
> >are (i.e. at the far end of a planet-sized view volume) and 
> scale them down
> >accordingly?. This surely would give incorrect parralax 
> between the distant
> >objects
> >
> >Also you need the planets to be of enormous size so that the 
> front clipping
> >plane doesn't cut through the planets fine detail when you 
> are in very
> close
> >(lets say an ant view for example). Which again buggers the 
> zbuffer, since
> >you're using a planet sized view volume.
> >
> >Any ideas?
> >
> >Regards,
> >
> >Sam.
> >
> >
> >
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> 
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