THE RBD BULLET SOLVER SOP

1 Drop down a RBD Bullet Solver SOP and plug in the fractured geometries’ high-resolution geometry into the first input, proxy pieces into the third input, and the animated geometry created in the last section in the fifth input. Constraints are not needed, but can be used in select cases where objects are constrained to guided pieces but are not actually guided themselves.

2 On the Guided Simulation tab of the RBD Bullet Solver SOP, enable Use Guides. Test out the simulation. Important parameters to play around with include Guide Strength, Blend, Instantaneous Linear and Instantaneous Angular Thresholds.

3 Guide Strength determines how faithfully each guided proxy piece follows its respective guide. In this project, Guide Strength was animated from a value of 3 at frame 108 to a value of 1.5 at frame 122 so that pieces are more strongly held to their guide during the initial twist. Additionally, the distance to strength parameter was decreased to a value of 3 so pieces that moved three units away from their guide geometry would have their strength multiplied by 0.25, resulting in the pieces becoming unguided. This is useful when a high overall Guide Strength is used, so that there are no unnatural pieces that are far from their guide.

4 The Blend parameter on the Simulation Settings tab is another important parameter, to help dampen the simulation and ultimately reduce jittering of pieces, at the cost of accuracy to the animated geometry. In this project, Blend was animated from a value of 0.7 on frame 6 to a value of 0.5 on frame 55, back up to a value of 0.6 at frame 120.

5

Linear and Angular Instantaneous Threshold parameters were animated down so pieces had a higher likelihood of becoming unguided during the peak intensity of the animated geometry. Linear Instantaneous Threshold was animated from a value of 1.5 at frame 68 to a value of 1 at frame 118. Angular Instantaneous Threshold was also animated down from a value of 10 at frame 68 to a value of 9 at frame 118.