Obi Rope

Obi is an advanced particle-based physics engine capable of simulating a wide range of deformable material behaviors, capable of running both in the CPU and the GPU. (CPU mode depends on the Burst, Jobs, Collections, and Mathematics packages, GPU mode requires compute shader support).

With Obi Rope you can create ropes and rods in a matter of seconds, with complete control over their shape and behavior: Oriented particle technology allow Rods to offer torsion/twisting effects. Ropes are more lightweight and can be cut/resized. Bones can be used to add secondary motion to character bone hierarchies. All of them can collide with the environment and with each other, can be attached to rigid bodies and offer two-way coupling with them.

This system is NOT based on rigid bodies and joints, unlike other rope solutions. This is based on XPBD particles which makes it more lightweight, detailed, and unconditionally stable.

Links

Obi Website

Community and Support Forum

Features:

- Non-linear, non-destructive rope editing using splines. Get instant feedback on how your rope looks while editing it!.

- Procedural smooth mesh generation using splines, complete with tangent space updating and normal map support. No need to manually generate geometry for your ropes.

- Adaptive curvature-based realtime mesh decimation: straight sections of a rope can generate simpler geometry than curved ones.

- Change rope length at runtime.

- Tearable/cuttable rope.

- Closed loops.

- Two-way rigid body interaction.

- Modular solver: don't waste performance, only use the constraints your rope needs.

- Per module adjustable solver iteration count.

- Independent stretch/bending stiffness.

- Easy-to-use editor particle tools: selection, brush selection, paintbrush, property smoothing...

- Supports all standard Unity colliders.

- Automatic camera culling: non-visible ropes do not update their simulation.

Release Notes

### [IMPORTANT] Obi 7 is a major update. If you're updating from an older version, it will require you to redo the setup most of your existing Obi-related functionality. It is recommended to use Obi 7 on new projects only, or if you must update an existing one, plan accordingly and set aside some time to perform the update.

## [7.1]

### Added

- ObiBone now exposes one particle group per bone in the hierarchy, allowing to easily use attachments.

- New ObiBoneOverride component that allows to override curve-driven properties for a specific sub-hierarchy.

- Solvers can now optionally enforce boundary limits, so that particles can't go outside those limits. This is often more convenient than manually placing invisible colliders for the same purpose.

- Dynamic ObiParticleAttachments now have a "projection" boolean, when enabled it forces the rendered position/orientation of the attached particles to match that of the attachment location, even if the constraint doesn't fully converge. This is useful to avoid visual gaps under extreme conditions.

- Actors now have a "mass scale" parameter, that multiplies the mass of all particles in the blueprinyt at the time of loading it into the solver. This is handy to create actors of different masses without the need to create a new blueprint.

- ObiForceZones now have a "color" parameter, that can be used to change the color of particles entering the zone.

### Changed

- Improved performance for large amounts of static colliders: they're not processed at all during ObiSolver.Update().

### Fixed

- Null reference exception when using a ObiRopeExtrudedRenderer that doesn't reference a section asset.

## [7.0.5]

### Added

- New pinhole constraint type and ObiPinhole component, that allows to constrain ropes to a point in space while allowing it to slide trough it. Supports two-way rigidbody coupling and can be motor driven.

### Fixed

- Erratic bend/twist constraint behavior when darboux vector is close to identity.

- Crash when attempting to bake ObiRopeExtrudedRenderer paired with an ObiPathSmoother that uses a non-zero decimation factor.

- IndexOutOfRangeError when having ropes using multiple different section assets and disabling all rope instances using one of them.

- InvalidOperationException in Burst backend when having simulateWhenInvisible = false and solver not seen by any camera.

## [7.0.4]

### Fixed

- Bug that caused inactive particles to still be rendered by ObiInstancedParticleRenderer.

- Bug that preventing pin constraints' break threshold from working when using the Compute backend.

## [7.0.3]

### Added

- Object layer support for all renderers.

- New "Synchronous Fixed" solver synchronization mode, similar to Obi 6, offers tighter integration with rigidbody physics.

- New "Tangled Ropes" sample scene.

## [7.0.2]

### Fixed

- Solvers not placed at the scene origin would result in actors having incorrect motion blur in HDRP.

- Fixed issue when disabling all solvers and colliders simultaneously: ipon re-enabling them, the colliders would be ignored.

- Issue withe ElectricalSparks sample scene, ObiRopePrefabPlugger sample component may sometimes thorw an exception dependin on Unity's OnEnable call order.

- Rope would sometimes disappear when using aerodynamic constraints with zero wind in Burst, due to a math.project returning NaN. Replaced with math.projectsafe.

## [7.0.1]

### Added

- BakeMesh functionality to ObiRopeChainRenderer, you can now export baked chain meshes.

- Render layer mask support to all rope renderers and particle renderers.

### Fixed

- Sceneview mouse lookaround in flytrough mode (right click + drag) didn't work in the path editor in Windows.

- Having a ObiParticleRenderer with no material applied resulted in a exception in builds due GetInstanceID() returning 0 in editor but raising a nullref exception in the build.

## [7.0]

### Added

- Compute shader based GPU solver backend.

- More efficient solver update cycle, that also removes the need to have ObiUpdater components.

- Aerodynamic constraint support for ObiRope, ObiRod and ObiBone.

### Changed

- Rendering system is now fully multithreaded, integrated with the solver backend.

### Removed

- Native library based 'Oni' solver backend.

- ObiUpdater and all derived classes have been removed.