Ziva Dynamics Controls Precise Animations for Cartoons and Digidoubles

The developers at Ziva Dynamics have made a new contribution to the work of modellers and animators who use character simulations. With their new software update, Ziva VFX 1.7, and the development of Art Directable Rest Shapes (ADRS), artists can make characters conform to extreme shapes without losing their dynamic properties, speeding up the tasks involved in creating cartoons and digidoubles.

Artists can now adjust a character’s silhouette with simple sculpting tools to quickly achieve a new look required for a story or client. Once the goal shape is established, Ziva VFX can morph to match it, maintaining all of the dynamics embedded to define the character before the change. Whether unnatural or precisely realistic, ADRS can work with any shape and largely avoid complex setups and excessive corrective work.

Reverse Engineering

What makes using ADRS quicker and easier for artists is that they can define the exact shape of the character, or a portion of it, that they want to hit when it is being animated – in advance of running the simulation. This causes the simulation – the underlying algorithms and processes that drive Ziva’s method – to essentially reverse engineer itself to exactly match the desired shape.

Existing methods apply force to the tissue's vertices in order to make them fit a supplied target mesh in world space. That approach gives artists a lot of control over the position of the simulated vertices but the force will stiffen the behaviour of the tissue and limit how much it can react to outside forces in the environment like inertia, gravity, muscle contraction, collisions and so on.

In contrast, when using the rest shape technique, the artist pre-processes the sculpted mesh in order to remove the effect of the simulation from it – that is, adding together the sculpt and the simulation will arrive at the desired shape without having to put extra forces on the vertices of the tissue, which in turn leaves those vertices free to react naturally to other forces.

Development

The Art Directable Rest Shapes functionality has been in development for about a year, in collaboration with several VFX and feature animation studios whose projects and art styles differed quite a lot. However, all groups were essentially looking for tools with the same qualities – extreme accuracy and more control, without compromising the dynamics that sell a final shot.

The release of Ziva VFX 1.7 follows many months of new creature work from VFX studios including Scanline VFX for the ‘Game of Thrones’ dragon, Milk VFX on ‘Good Omens’ and Pixomondo’s animal characters for ‘A Dog’s Way Home’.

Original muscle sculpt ...

Ziva’s dynamics in particular are designed to mirror the fundamental properties of nature so that CG characters will move, flex and jiggle naturally as they would in real life. This includes skin sliding and interaction between a character's form and external forces like wind and water. Approaches that require manually sculpting the desired results after the simulation would interfere with those natural properties of the sim, as well as demand a lot more work from the artists.

For characters in animated movies that don’t need to follow real world physics, ADRS can rapidly alter and exaggerate key characteristics, allowing teams to be expressive and creative without losing the power of secondary physics. For live action films, where the use of digidoubles and other photorealistic characters are growing and realism must be perfect, ADRS can minimise the setup process when teams want to quickly tweak a silhouette or make muscles fire in multiple ways during a shot.

... Muscle after applying a rest shape.

Using ADRS

A number of studios that have been using ADRS want to reduce their reliance on shot sculpting and corrective workflows. Josh diCarlo, who is Head of Rigging at Sony Pictures Imageworks said, "Our creature team wants to develop Art Directable Rest Shapes to augment our facial and shot-work pipelines. Ziva VFX 1.7 can potentially take weeks of work off of both processes and improve the quality of the end results at the same time.”

To use Art Directable Rest Shapes, artists duplicate a tissue mesh and sculpt their new shape onto the duplicate, They can then add the new geometry as a Rest Shape over the critical frames. This will intuitively morph the character in a natural way, creating a smooth, distinctive deformation that adheres to wisely varied artistic direction.

“Art Directable Rest Shapes allow us to nail difficult anatomical details in an intuitive way while still taking advantage of Ziva’s physical simulations,” said Seong Joon Lee, CG Supervisor at MPC and an early adopter of Ziva VFX 1.7. “This helps us depict complex physical motion in a realistic way.”

As well as ADRS, Ziva VFX 1.7 will also include a new zRBFWarp feature, which can warp NURBS surfaces, curves and meshes.  www.zivadynamics.com