[sldev] Packing alogrithm behind LAND_LAYER_CODE part of aLayerData message

[Jesse Nesbitt]

I believe that the OpenSim project has a working LayerData encoder, you
might want to check with them.
I know that John Hurliman and Adam Zaius have done LayerData work, if you're
lucky one of them might chime in.

On 3/14/07, Tleiades <tleiades at hotmail.com> wrote:
>
>  I decided that maybe I should try to tell what I have already figured
> out, and what hunches I have.
>
> This specific subtype of the LayerData message starts with a GroupHeader,
> containing a patch size, a stride and a repetition of the layer type. I
> haven't figured the exact purpose of the stride yet, but believe I have the
> other two fields pinned down.
>
> Next follows a number of patches, each patch begins with a header. The
> only things in the header I have been able to determine is that quant_wbits
> (in part) encodes the size of the following numeric data, and that patchids
> seems to reference some sort of co-ordinate system.
>
> Following the patch header is a bitpattern, which depending on bits turned
> on or off either idicates zero, negative or positive number, the size of the
> numbers are determined by the quant_wbits field. My guess is that the
> numbers are height encodings.
>
> In short the message encodes a packed height field, but I really have no
> clue on how to combine the individual LayerData messages into a complete
> height map.
>
>
> ----- Original Message -----
> *From:* Tleiades <tleiades at hotmail.com>
> *To:* sldev at lists.secondlife.com
> *Sent:* Wednesday, March 14, 2007 6:46 PM
> *Subject:* [sldev] Packing alogrithm behind LAND_LAYER_CODE part of
> aLayerData message
>
> Hi
>
> I've been trying to figure out the algorithm behind packing and decoding
> the LAND_LAYER_CODE part of a LayerData message. I'd like to get the broad
> picture of how that data is encoded, but I seem to get lost, not seeing the
> forest, because all the trees get in the way.
>
> Is there someone who can provide me with an overall picture of the
> algorithm or point me to some url's explaining the algorithm?
>
>
>
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-- 
--Jesse
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