Re: [Algorithms] Huge world, little precision

[John R. <jra...@in...>]

I have had to deal with this problem and, so again, have many people.

The GPU problem is a relatively easy fix.

On any given frame you are going to do frustum and other culling tests to
get just the objects 'in view'.  Just re-work your pipeline so that wherever
in the world your camera is located make,for that frame, be considered 0,0,0

Downsample all of your 64 bit floats or fixed point integers relative to the
camera location.

Then render everything and it is perfect.

I did this on Planetside to avoid texture swimming and other artifacts when
a player was near the edge of a map and it worked just fine.

John

-----Original Message-----
From: gda...@li...
[mailto:gda...@li...] On Behalf Of George
van Venrooij
Sent: Wednesday, February 28, 2007 6:40 AM
To: Game Development Algorithms
Subject: Re: [Algorithms] Huge world, little precision

Thanks for the link to the article, it is indeed very true :-)

I understand the possible solutions to maintain precision in the dataset. 
But the biggest problem I am running into, is how to "mold" that data for 
the GPU when rendering. Obviously the GPU cannot render fixed-point 
vertices, so they need to be processed before sending them. And when sending

them they should preferrably be in view-space.

My goal is to keep that processing down to a minimum, but the nature of the 
data causes a problem:

The problem with a ROAM-like algorithm is that the mesh can (and usually 
will) change every frame. And the viewer's position will change as well. The

only viable solutions I see for this are:

1. Translate the generated vertices to view-space before rendering every 
frame (expensive for large meshes)
2. Generate the planet in "patches" that have their own local coordinate 
system, and render each "patch" separately. This is also something that Jim 
Schuler suggested (this probably requires doubled vertices or triangles on 
the "seams" of the patches and hope they fit together nicely when rendered)

I'm wondering if there is some kind of third option...

Regards,

    George
    ge...@or...
    www.organicvectory.com


----- Original Message ----- 
From: "Conor Stokes" <bor...@ya...>
To: "Game Development Algorithms" <gda...@li...>
Sent: Wednesday, February 28, 2007 13:12
Subject: Re: [Algorithms] Huge world, little precision


> There are also lots of neat bit tricks you can do with fixed point integer

> coordinates at an object level for building acceleration structures.
>
> ----- Original Message ----
> From: "lo...@fr..." <lo...@fr...>
> To: Game Development Algorithms <gda...@li...>
> Sent: Wednesday, February 28, 2007 8:23:32 PM
> Subject: Re: [Algorithms] Huge world, little precision
>
> 64 bit integers?
>
> Anyway, I believe you should read TomF's blog, as it dealt with this 
> subject:
>
>
http://home.comcast.net/~tom_forsyth/blog.wiki.html#%5B%5BA%20matter%20of%20
precision%5D%5D
>
> Regards,
>
> -- Emmanuel Deloget
>
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