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Huge territories.


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#1 Broadleaf   Members   -  Reputation: 154

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Posted 31 December 2012 - 07:12 AM

I want to create huge territories. Preferably generated (POLYGONAL, NO CUBES), builded like Vue's , or Dreamscapes's, based on real world.

What i want to avoid is huge numbers problem. Like in minecraft if you go to what they call "Far lands", due to

pos_x 120123123.12312301239 , everything goes into astral and bug/glitches/probably lags.

 

I assume i can switch player local coords parent, rebinding it to terrain pieces (2km square for example), this will cut lags to some level.

But still, terrain will have world coords. So i imagine i must create different root's, for each 100km^2 for example.

And switch them under player.

Any thoughts on that?



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#2 Tribad   Members   -  Reputation: 887

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Posted 31 December 2012 - 07:37 AM

If you move your position up high over the area you must do something to display the adjacent areas.

The recalculation of the positions, even if it is only addition of values, may take a long time according to the amount of data you must re-root.

 

So one of the questions to answer is the amount of data you have to manage



#3 Broadleaf   Members   -  Reputation: 154

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Posted 31 December 2012 - 07:57 AM

If you move your position up high over the area you must do something to display the adjacent areas.

The recalculation of the positions, even if it is only addition of values, may take a long time according to the amount of data you must re-root.

 

So one of the questions to answer is the amount of data you have to manage

 

 

huge. Planning to have that tradeoff, so player will wait for region to load.

The problem is not rendering landscape, i can render that.

Also i think paged geometry will solve some performance issues, objects

will load/unload in 3 squares radius. I think it's solved, i don't think loading

screen will be an issue.



#4 SeraphLance   Members   -  Reputation: 1453

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Posted 31 December 2012 - 11:43 AM

Several languages and libraries have support for arbitrary-precision arithmetic.  That gives you a theoretically infinite resolution at the cost of a performance hit in your computations.  I think the far lands are an artifact of older versions of minecraft using floating-point precision for coordinates, causing issues at very large numbers, or at least that's my guess.

 

You'll need to retrofit all of your procedural generation functions to operate on the new bignum-ish constructs instead of float/double primitives, but that's not terribly difficult.

 

Like you said, you can bind larger chunks of terrain to a smaller coordinate resolution, but that just curbs the issue.  If you're that hell-bent on not having rendering issues at extremely far-out distances, I don't think you'll be satisfied there.

 

EDIT:  If you do use an arbitrary-precision arithmetic library, you'll probably need to simulate your floats.  That is, one number for the integer, another for the mantissa.


Edited by SeraphLance, 31 December 2012 - 11:44 AM.


#5 samoth   Crossbones+   -  Reputation: 5032

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Posted 31 December 2012 - 12:53 PM

The single most important thing to learn when "huge" and "coordinate" coincide is that floating point is usually the wrong tool. And no, using double precision doesn't make it better.

Use integers (with fixed precision). With 64 bit integers, you can represent 1013 kilometers at 1 millimeter precision. This is a size close to the size of our galaxy.

No rounding, no "glitches", no unexpected stuff.

Interesting read: A matter of precision.



#6 Cornstalks   Crossbones+   -  Reputation: 6991

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Posted 31 December 2012 - 01:04 PM

The single most important thing to learn when "huge" and "coordinate" coincide is that floating point is usually the wrong tool. And no, using double precision doesn't make it better.

Use integers (with fixed precision). With 64 bit integers, you can represent 1013 kilometers at 1 millimeter precision. This is a size close to the size of our galaxy.

You can use doubles to get 1012 kilometers at 1 millimeter precision too... I would argue that using double precision does make it better, seeing as a float only gives you 103 kilometers at 1 millimeter precision.


Edited by Cornstalks, 31 December 2012 - 01:06 PM.

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#7 amrazek111   Members   -  Reputation: 695

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Posted 31 December 2012 - 02:45 PM

You might find http://scottbilas.com/files/2003/gdc_san_jose/continuous_world_paper.pdf interesting.  They talk about the precision issue under "terrain implementation."  It might give you some ideas



#8 Broadleaf   Members   -  Reputation: 154

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Posted 02 January 2013 - 09:16 AM

Thank you for aswers, i've learned something new.






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