Szymon Kapeniak


About Me

CG Supervisor


Recent Forum Posts

Mantra Light Shaders Nov. 14, 2018, 4:15 a.m.

Checkout ASAD Light/Shadow SHOPS as they are comprehensive source of information on how to write custom light shaders.

Ziva muscles vs Houdini muscles Oct. 9, 2018, 2:56 p.m.

Ziva FEM solver is specifically designed for muscle simulation which enables many optimizations. Main challange for the solver in case of muscles is interpenetration and collision between muscles, and in fact this is the slowest part of Houdini FEM. We run sims with 50+ muscles in minutes without piecewise collisions. I can't really complain. Typical scenario is using SDF approximation of muscles for fast collisions with a very little lost of accuracy in terms of volume preservation. Houdini, being general FEM solver, doesn't do that (it's a pity FEM solver does't allow micro solvers for custom collision handling, but this might be technically tricky as I presume since collision response has to be efficiently injected into finite elements matrix).

Personally I don't see big advantage of Ziva over Houdini muscles. And as always, Houdini flexibility will be huge win for any advanced system. Do any complicated character with skin, mixed muscles with linear skinning, post process corrections and blend shapes, and you will see the difference.

And yes, Vellum (XPBD) is a new chapter for muscles in Houdini.

Cloth's slow speed March 23, 2018, 10:47 a.m.

That said, I am pretty sure Houdini's docs say that Houdini uses tets and tets exclusively for FEM - and I *think* I remember it also saying that a FEM cloth is being created by adding virtual thickness

We are talking about the same thing. Virtual thickness can be modeled by placing additional vertices (labeled ghosts as they don't collide) around triangles to form tets with them. The only controversy we have here is whether these tets are formed from the original mesh (thus following its density), as I speculate, or built upon some parameters as in case of Solid Object (as suggested by you afaik). I've not seen such possibility for cloth object, thus my confusion. I think we have to wait for SESI to answer this. Also birds say there is new solver coming, so our findings might quickly become obsolete.

Yes, Houdini uses tets solely, but general concept of FEM allows other elements too. You could model and simulate cloth from triangles or quads without any virtual thickness, but then you need a way to model 3rd dimension behavior of cloth material.