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david's really interesting pages | palaeoart, animation and stuff
david's really interesting pages | palaeoart, animation and stuff

SubDivs… got ’em. Or do I? FMX2013 report… Bill Polson

I’m a subD addict – I use them all the time. I model with them, rig low-density cages and apply displacement maps that apply on subdivision surfaces – the advantages over straight up polygons and nurbs surfaces is just stellar. Pixar has made this technology open source and aside from Autodesk, has worked with Luxology, the makers of my modeler of choice, so it’s in my hands, right? Pixar! Dudes!

Well, that’s what I thought. Like most cg artists I know, I was sure that I was profiting from this technology. Truth is… not fully.  At FMX2013, Bill Polson made a great playdoyer for why the industry as a whole will profit from subdiv technology becoming a standard. And that’s subdiv technology, not subd… respect the authors: Ed Catmull, Mark Meyer, Tony DeRose (Pixar), Charles Loop (Microsoft Research) and Matthias Niessner (Universität Erlangen-Nürnberg).

The advantages over polys and nurbs are well-accepted, and AlexK wrote them up in his review, so I’ll point to the bigger deal that had escaped me… computational efficiency.

Before you tune out, my artistic friends, let me rephrase that into 1) near-realtime feedback of dense, sculpted meshes that hold up under extreme deformation and 2) consistently transfer across various applications, including games engines.

There is no 100% implementation now available that allows all this (Maya and mudbox present the closest thing right now), but the promise is there – in the form OpenSubdiv. Bill talked about the choice to use the Microsoft public license because it includes the patents behind this technology (!!!) but also causes some legal issues which are preventing the Blender foundation from full implementation. A glitch which – Bill assured us – is being addressed.

Another key word is hierarchical layering – meaning that each subdivision level that is sent to the gpu for rendering can be processed. So things like displacement can be calculated in on the GPU while the low-density base mesh is being deformed on the CPU – in iterations. The importance of this can be summed up as efficient level-of-detail processing. For further technical advantages, I point you to this autodesk video highlighting their cooperation.

YouTube Preview Image

I’d like to sum the advantages from the POV of us artists, because we need to be vocal about getting this implemented across the board… from CAD software to games to film and vfx software. A world of play-nice toolsets and immediate artistic feedback that you can trust to hold up across pipelines is just too necessary.

1) model clean, lean meshes that subdivide according to defined creasing values (or edge-weighting) and send these meshes from one tool to another with consistent results (go to 26:50 in the video above)
2) get rapid feedback of detailed surface displacement not only while sculpting, but while animating and and lighting
3) manage large scenes efficiently via level-of-detail controls that optimize hardware usage. This applies to distance-from-camera controls as well as to localized displacement effects such as Merida’s horse Angus plodding through snow.
4) know that your work is compatible with further feature sets like ptex texturing

SubDivs? You know you want ’em!

There are 6 Comments to this article

Heri says:

welcome to world of level-sets !

or subdivs for geo……

d maas says:

yeah… of course Heri’s in the know.
Was a bit of a surprise to me, because i thought I’d understood subdiv technology.

Heri says:

i was the same after 2008 i got into level sets with particle caches…
very similar with different interpolation methods….

d maas says:

Is that being addressed by one of the new open formats? There’s one for particle caching I believe…

Heri says:

only inhouse tools…. but thats for display

more import is loading caches in levelsets… almebic should do it

drip | david’s really interesting pages… says:

[…] rousing some decent interest in SubDiv technology and linking to modo and cgTalk, I thought I’d point to one of the […]

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