GiL the B's polygon subdivision script showcased for 2.105

Hi Louise Friends

2.105 is ready for download from:

www.seamless3d.com/download

The goal of this version has been to run Gil's subdivision script
GiL showed me this very interesting script late last year when it was written all in JavaScript.


To witness GiL's script converted to Seamless C++ running from his site:


click on the web file button:



and paste in the fowling url into the worldUrl field:

http://giltheb.net/technology/20060712_doo-sabin.smls


then click go.



The smooth shape to the right is created from the box type shape to the left.

The density of the polygons depends on the value of passe

If passe is set to 1 the number of polygons is doubled. If set to 2 it is doubled again and so on.

The code generated by Seamless's built in compiler wont be as fast as VC8's code when compiled for Release but I was very eager to compare the speed of Seamless's script to Contact's script engine. I tried passe set to 4 and this was the result for my computer:

Seamless3d C++: just under 9 seconds
Bitmanagement Contact 7 JavaScript just under 326 seconds

This makes Seamless's built in compiler 36.2 times faster to generate this many polygons!

Please note in the output wrl all the dstIfs's coordIndex and dstCoord's point should be emptied and all of the MF fields for the Script node should be emptied too using a text editor.

Many thanks to Gil for letting his wonderful script be used as a demonstration for this version of seamless

Ah yes I was playing around with Gil the B's proto a few days ago, seems it doesn't like certain meshes. Now i'm wondering if the seemless3d version doesn't suffer from this problem.

Hi Fab
Because little was changed apart from things like integers being used instead of floating point numbers for some of the variables, I doubt the functionality will have changed. I remember gil saying last year that his script will only work for 4 sided polygons and I think he said that the shape should not have holes.

This should not be a problem for making the body for something like an avatar. The hair and some accessories might be better made separately using some other technique.

I would like to try making an avatar like this using seamless to create the control points but because the seamless node only supports triangles I can see the need for at least some bare minimum function to be added that lets the user order the index of triangles so that triangles can be paired so that later they can be easily converted to 4 sided polygons.
VRML97/X3D requires planar polygons (flat). However this does not cause problems for the way hardware renders non triangle polygons and it is easy to convert any kind of polygon to triangles for the purist.

Here is a different technique for polygon subdivision that works for triangles:

http://sfb-603.uni-erlangen.de/DOWNLOAD/A1/3dim2001_subdiv.pdf

but this triples the poly count instead of doubling them because each triangle is split into 3 triangles from it's centre for each pass. Also shapes typically are noticeably smoother looking when the polygons run in strips rather than when they are zigzagged, so working with 4 sided polygons (or triangles grouped into 2s) has this advantage too.

gil explains some things not to try here:

http://www.seamless3d.com/forum/viewtopic.php?t=31

Thinking about this more I should have said gil's script quad drupels the polygons if it were to split each quad into 4 quads but apparently my understanding is all wrong anyway lol.

I have found since that gil's script is more complex than this and I can now see his example also generates some triangles (at the corners), not just quads.
Understanding this I tried inputting just triangles and found this works fine so there is no need to convert to quads first which makes things easy for editing in seamless however I have found not all combinations of triangles work so I am still not sure what all the rules are yet

good news about Gil

https://closed.forumactif.com/3d-gallery-f26/giltheb-gil-t2295.htm#67933


reedit :

oupsssss , sorry , the site is empty