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Jaggedge
PostPosted: Fri Aug 15, 2008 6:53 am    Post subject: Limiting Grome to 16bit Reply with quote



Joined: 08 Jul 2008
Posts: 56

Hi, my colleagues tell me that Grome works with 32bit floating points for its height values and I was wondering if there's a way to limit its units to 16bit. The reason is because the engine that I'm exporting my zones to uses 16bit for heights and I want to be 100% sure that nothing gets lost in translation. Please correct me if there isn't actually any problem and I'm worrying too much, haha Laughing
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ALicu
PostPosted: Fri Aug 15, 2008 7:11 am    Post subject: Reply with quote



Joined: 12 Feb 2007
Posts: 1326

Hi, yes Grome uses 32bit floating point. From my experience saving from 32bit to 16bit unsigned int is not a very big problem. Artifacts (terrain surface stepping) can appear when you have very subtle changes in the surface and also a very big altitude difference between the minimum and maximum.

Basically in 16 bit you have maximum 65535 distinct values. So, when you have a terrain between 0 and 2000 meters (in floating point) you export this into 0, 65535 integer range. 2000/65535 is around 0.03 which means you can have heught differences of 3 cm between 2 vertices and still be correctly recorded.

Also, to be noted that in a game you actually render floating point values (vertices kept as floats). So by exporting into 16 bit you have an intermediary step (32bit float -> 16bit uint -> 32bit float). If this conversion becomes a problem (which may very well not be the case) you may consider exporting directly into your engine format (create an export plugin to custom format).

Regards,
Adrian L.
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Jaggedge
PostPosted: Mon Aug 18, 2008 2:47 am    Post subject: Reply with quote



Joined: 08 Jul 2008
Posts: 56

Thank you for that clear and detailed explanation, ALicu Smile So, rather than working with 32bit and then exporting to 16bit, is there a way, within Grome, to work with 16bit directly? I just want to explore this possibility Laughing
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ALicu
PostPosted: Mon Aug 18, 2008 6:09 am    Post subject: Reply with quote



Joined: 12 Feb 2007
Posts: 1326

In current version of Grome there is no way to force it work at 16bit. Version 2.0 has in plan multi precision heightmap layers (you can work with 8, 16 bit integer, 32, 64 bit floating point heights, you can even combine them in the stack). For now, I think you should not worry too much about it, we have many clients using conversion to 16 bit without any visual noticeable differences.
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Jaggedge
PostPosted: Tue Aug 26, 2008 2:13 am    Post subject: Reply with quote



Joined: 08 Jul 2008
Posts: 56

Right, thanks for the reply ALicu Very Happy
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