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Mesh pivot point?


Moo Spyker
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Hint to save texture faces (materials)

I was running low on texture faces with  a mesh and needed to set the bounding box and pivot point. I tested if it's possible to add so small markers in the bounding box corners that they won't show, and then they can be part of any existing texture face.

I used corner marker triangles of size 0.01 mm,  so on a 2000 pixel screen the camera needs to be closer than 2 cm from the marker to make it fill one pixel,  which makes them practically invisible no matter what color they have. Still the tiny triangles defined the bounding box correctly.

(The size was chosen so that the difference of the corner marker coordinates can be calculated accurately to be non-zero with the SL 32-bit floats, though I don't know if the server and mesh uploader uses 32-bit floats like LSL does.  The 32-bit float  has 23 bits precision, about seven significant numbers, hence  0.01 mm is ok for up to 64 m sizes,  as 64.00001-64 requires 22.6.bits to give non-zero result).

 

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Excellent idea.

The mesh upload format actually uses 16 bit integers for position information, from which floats are recovered by multiplying with a scaling vector. (For a given bit size, the integer has constant absolute accuracy over its whole range, which is more accurate than the float at the high end because the float 'wastes' bits on the exponent).There is a constant, LL_DEGENERACY_TOLERANCE, that determines the smallest size below which faces will be ignored, but the code using it is a bit complicated and looks as if it takes shape into account too.  If you want a definitive size/shape minimum for this technique, you could table a question in the Content/Mesh User Group agenda.

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