Goal Pose

Goal posing is a very powerful art direction technique to create animation-driven physics simulation. It  takes an animation and allows to manually set areas where physics may deform and transform the animation. This advanced technique can be used to overcome geometry problems like pinching and self-intersections in animations, fix objects in space, filter collisions on a per node basis, introduce secondary motion, partially skin cloth, loop animations, and many more. 

Goal posing is used on Carbon Morph, Carbon Cloth and Carbon Tetrahedron nodes.

 

Deforming Bodies

Morphs are intended to turn parts of an animated collider into cloth, which usually is targeted at solving animated collision geometry issues, like intersecting armpit or leg geometry.

Cloth pinched between morph objects.

 

Simulation Looping

On the other hand, goal posing a Carbon Cloth allows the creation of sophisticated effects such as seamless cloth simulation looping. A typical application for looping would be a flag, or a fashion video of simulated cloth, of say 5 secs, that seamlessly loops. Its also possible to create a sophisticated interactive application with a decision tree of different transitions so that the cloth behavior change be changed in some way (maybe increased wind speed) and it seamlessly transition to a new loop.

 

Looping a flag in the wind.

 

Secondary Motion

Secondary motion effects and cloth skinning often go hand in hand. The sequence below shows the various stages of a skinned and goal posed cloth varying from kinematic (left end of the skinned cloth) to constrained to fully dynamic (right end of the skinned cloth).

 

Comparison of purely skinned geometry (left) versus a goal posed simulation (right).

 

Simulation Speed-up

Similar to the usage for Secondary Motion, goal posing can be utilized to gain simulation performance. In cases like the arm with sleeve, as seen above, apply a base goal skin strength which keeps the cloth geometry in place for a static goal pose. This means that the goal skin strength balances out the effects of gravity on the cloth. The underlying physics solver therefore does not have to rely on a high number of iterations to counter-act the extension of fabric under gravity. Since the simulation time strongly depends on solver subdivisions and iterations, a reduction of iterations can drastically speed up the simulation.

 

Collisions Control

Goal posing can also be utilized to dynamically turn collision on and off on a nodal basis by switching between kinematic and dynamic states.

 

Activating and deactivation collision via goal posing.