ok, posted this on ehear hoping for a sesi reply (don't we all)

anyone care to quickly explain the role of the new and not-so-new point attribuites of the L-sys/polywire SOP
(ok, $WIDTH is self-explanatory)

is $GEN? the generation at which the point appeared? (not quite, it seems)

$LAGE? anyone? (is it the vertical increment*divisons?)

for instance what is $ARC? (it had a logic to it in the attrib spreadsheet, just want to make sure…)

(any “unlisted” vars )


since we're on the toipc of point attributes….would it be too much to ask for a sortable attribute spreadsheet (along 3 or more “keys” pretty please )

YES…someone does use the thing….. :wink:

oops, this post tuned into a bundle of requests!
please sir, may I have some more?

Cheers!

Well, most of them are at Siggraph so you won't get your reply so soon.

as long as it's during THIS lifetime! :?

As of 5.0 (4.9.466 to be precise) several improvements were made to the lsystem sop to better support the polywire sop. Here's a copy of what I wrote at the time…

• The point width attribute is multiplied by the thickness value
  of the lsystem, so will match the diameters of the tube
  generation.
  
• Generations over 127 produce the correct generation number.
  
• When point attributes are generated, we create more than just
  the width attribute:
  
• segs ($SEGS), an integer point attribute for the number of
  segments (rows) tubes leaving that point should have.
  
• div ($DIV), an integer point attribute for the number of
  divisions (columns) tubes leaving that point should have.
  
• lage ($LAGE), the age of the point in the lsystem.
  
• arc ($ARC), the arc length from that point to the root of
  the lsystem.
  
• up ($UP[XYZ), the up vector for the tubes birthed at that
  point.
  
• gen ($GEN), the integer generation of that point.
  
  
• When point attributes are created, the system's points are
  automatically sorted by generation. This means point numbers
  will match from generation to generation, allowing motion blur,
  etc.
  
  
  lage is the vertical increment of the lsystem from the tube parameter folder. Either arc or lage makes a good value for the v texture coordinate. If you go to the preset menu of the polywire sop (in 5.5 you'll have to expand the hidden bar at the top of the parameter window) you'll find a “forlsystems” preset which fills in most of the stuff from the lsystem variables. For texturing I usually put in ($ARC, $ARC2) in the v texture parameter as well.
  
  I hope this clarifies things.
  
  - Jeff

thanks a lot!…really appreciate it…

very insightful….still have a few quick ones…..hope you don't mind :wink:

arc ($ARC), the arc length from that point to the root of
the lsystem.

erm…does the arc length get normalized by default at each iteration?
if not what could one use to normalize it…

When point attributes are created, the system's points are
automatically sorted by generation.

YEAH!!!…… that'll immediately solve a big problem I had before with stamping! mmm I bet that's not the case for the polywire points though, it would be tougher to accomplish, right?

For texturing I usually put in ($ARC, $ARC2) in the v texture parameter as well.

nice!…tip to root continuous UVs!

and…erm….$ARC2? que? (nosy guy …)

thanks again! these were long standing questions, makes my world so much clearer! (that and daily coffe….)

BTW, any plans, talk, rumors, bribes, remote possibilities that “someone” might implement cellular L-sys?…not holding my breath, but if anyone gets a lot of free time …well… would be cool… he he he


Cheers!

Don't forget there might always be a demo file lying around to help.

Check out the demo\OPspecific\SOPs\polywire directory for an example on this question.