Finite Element Solver

A finite element solver is one of the main features of Side Effects Software's Houdini 13, released today. The new software also includes multithreaded particle architecture that Side Effects has integrated into Houdini’s existing dynamics setup. And there's a new lighting workflow for dealing with large datasets.

The Finite Element solver is remarkable - it analyzes the stresses on solid objects, then either bends or breaks each shape. FEA was covered in fxguide's Art of Blowing Crap Up, but this was in relationship to DMM, and the work of MPC's Kali. FEA being added to Houdini is a huge step in expanding the use of FEA in destruction pipelines.

fxguide spoke to Michiel Hagedoorn, who is a Senior Software Developer at Side Effects, and Jeff Wagner who is a Senior Technology Consultant on Houdini.



FXG: Is it a fixed number, non-adaptive Tetrahedralize (tet) Finite Element Analysis (FEA) system?

Side Effects: Houdini 13 does support changing topology and fracturing. You can even create your own fracturing technique as a geometry [SOP] network and combine it with our FEM solver, using a multi-solver/SOP-solver setup. It should also be possible to refine the tet mesh during the simulation using the Tetrahedralize SOP in a SOP solver.

FXG: Anything you can discuss your tet collision system?

Side Effects: When colliding with objects outside the solver, for example a Static Object, Houdini 13 supports both geometry-based continuous collision detection and volume-based collision detection. When calculating geometry-based collisions, Houdini 13 support collisions for the follwoing combinations: polygon-to-polygon, polygon-to-tet, and tet-to-tet.

Houdini 13 has a unique algorithm for global collision response that allows the entire object to respond realistically to local collisions.

FXG: Could you discuss tet collision detection in relationship to convexity?

Side Effects: There are no convexity restrictions on the collision detection. The collision works for convex as well as non-convex shapes.

FXG: How does FEA work with  Rigid Body Systems?

Side Effects: Currently, there is one-way interaction: FEM reacts to RBD objects, but not the other way around. You can make pseudo-rigid objects, by increasing the stiffness on your Solid Object. This gives you two-way interaction, since both rigid and soft body objects are then handled by the finite element solver.

FXG: Can you support plastic deformations?

Side Effects: Plastic deformations are currently *not* supported inside the solver. However, you have access to the rest positions as a vertex attribute. This allows you to create your own custom plastic deformation, for example, by interpolating between the current position and the rest position. For hardening, the various stiffness multiplier attributes can be increased in a SOP solver.

FXG: Have you implemented any geo caching or special geometry systems to speed up the system - like MPC's Kali's Rendertime chopping?

Side Effects: No. Not that I know of. We have Mantra which can handle a lot of geometry.

Although the ability to dynamically load and un-load geometry at render time with unbiased rendering is challenging, Houdini 13 approaches this in a more straight forward manner: Make Mantra even more efficient at loading in all geometry and tracing against everything. This is where Mantra excels. Side Effects is very effective in tackling extreme geometry sets and we have Houdini's threaded geometry tools to leverage inside of Mantra. This is a big advantage for Houdini-Mantra VFX pipelines.

"Houdini 13 offers more than just Finite Elements," says Fabiano Berlim, an FX Animator at Vetor Zero. “It is Finite Elements connected with the rest of Houdini. Now I can emit particles, that generate heat based on friction, which lights a fire, that causes a solid object to expand and break using the new Finite Element solver."

Houdini 13's other new features

Side Effects says that the new particle architecture has been fully integrated into the dynamics context to provide seamless interaction with other simulation tools. The vex-based framework is multi-threaded and allows for speeds up to 10x faster as well as cached results for scrubbing in the timeline. There are also new particle tools and forces including Axis Force which uses 3D volumes to control particles.


Houdini 13 screenshot.
Houdini 13 screenshot.
Final image.
Final image.

In order to handle huge datasets, Side Effects has upped the lighting workflow in Houdini 13 with a new data tree view for assigning materials and lights to the objects and groups found in Alembic files as well as Houdini’s new Packed Primitive objects.

"After extensive testing, we chose Houdini as our single lighting platform and Mantra PBR as the renderer for our future CG-features. In addition, we integrated Houdini in our pipeline using Alembic as the main geometry interchange format," says Bert Van Brande, Director of Production Technology, Reel FX. "Mantra's PBR physically-based rendering provides us with high quality images, an intuitive lighting workflow, and a solution to render geometry, effects and fur in a single package. We are also impressed with the speed of the renders and the modest memory footprint. On top of the workflow benefits, Side Effects backs their technology with best-of-class support."

Houdini 13 screenshot.
Houdini 13 screenshot.

Houdini 13 will also support OpenEXR 2 to allow for deep compositing of Mantra renderings in Nuke. Plus th new version incorporates OpenSubdiv from Pixar and integration of OpenVDB as developed by Dreamworks Animation. Other enhancements to Houdini 13 include an enhanced Bullet solver and FLIP fluid and Ocean FX tools.

Houdini 13 is available from Side Effects immediately as a download for $US1,995, with Houdini FX available for US$4,495. The free Apprentice Edition and the $99 watermark-free Houdini Apprentice HD are also available today.

You can find out more about Houdini 13 at Side Effects' website: http://www.sidefx.com/H13.


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