Mercuna v3.6 is one of our largest releases in recent years, with several significant new features, major workflow improvements, and over 100 fixes and refinements across the product.

Highlights include:

• Auto Drop Link Generation – agents can now descend from ledges naturally using drops, reducing the need for jumping and improving the quality and realism of movement.
  
• Unlimited Nav Grid Modifier Volumes – a new modifier volume implementation that removes previous limits on the number of runtime modifiers.
• Runtime Modifier Volumes without Actors or Components – create and manage nav grid modifiers entirely through code, enabling more flexible procedural and gameplay-driven systems.
• Nav Grid Build Debug Draw – inspect intermediate stages of the nav grid build process, including collected geometry, heightfields, and contours, making it much easier to diagnose generation issues.
• Lightweight FMercunaPath – a new lightweight, thread-safe path representation that can be created and queried from worker threads, making it well suited to Mass AI and custom large-scale simulation systems.
• Improved Query Filters – greater flexibility, additional context, and lower runtime overhead when implementing custom navigation rules.
• Motion Matching Support – generate path-based trajectories for Unreal’s Motion Matching system, improving animation selection by giving it a more accurate prediction of upcoming turns, stops, and speed changes.

  Mercuna – left, CMC – right
• Consistent Octree Builds – identical levels now generate identical octrees, preventing unnecessary nav data chunk changes and reducing source control noise.
• Unreal Engine 5.8 Preview Support – compatibility with Unreal Engine 5.8 Preview.

As always, this release also includes numerous stability improvements, performance optimisations, and bug fixes throughout Mercuna.

Release Notes

• Ground and Surface Navigation
  • New nav grid build debugging visualizations expose geometry, height fields, layers, and contours
  • Increase maximum modifiers per generation box to 32
  • Ability to create modifier volumes not associated with Unreal actors or components
  • Improve performance of ClampToNavigable with extremely large radius
  • Fix prism modifier components when used within Blueprints
  • Do not allow navigation on meshes with WalkableSlopeBehaviour set to Unwalkable
  • Fixed crash in nav testing actor when PathfindLatent couldn’t find a path
  • Small improvement in frame rate of polymesh debug draw
  • Improve nav grid debug draw colouring
  • Include Spline information when querying GetAllPathPoints for UMercunaSmoothPath
  • Add ability to specify usage spec to IsNavigable queries
  • Fix nav grid debug draw lines being offset
  • Ability to get all nav links on the current path from the Navigation Component
  • Fix very slow nav grid chunk merge in PIE when stats are enabled
  • Fix crash on shutdown while pathfinds are still running
  • Nav volumes outside of maximum nav grid size are now ignored with an error log
  • Fix assert if multiple grid builds are cancelled at a particular point during the build process
  • Fix polymesh triangulation issue
  • Improve avoidance for slowly reacting agents
  • Detect obstacles for avoidance earlier for slowly moving agents
  • Fixed misuse of speed multiplier in calls to MerDriver::CalculateAvoidance
  • Lower avoidance frozen threshold for low speed agents
  • Fix assert repathing through degenerate non-smooth waypoints
  • Fix to nav mesh where modifiers lie across generation borders
  • Fix rare assert during avoidance (SubtractInwardPlane)
  • Reduce distance that a nav seed will clamp down to the nav grid
• Ground Navigation
  • Automatic generation of nav links that drop down from geometry to the ground
  • Support driving Unreal agents using Motion Matching
  • Expose poly centre position to query filters
  • Expose nav link information to query filters
  • Expose more information on nav link queries
  • Option on nav grid modifiers to disable fast property updates. There is no limit to the number of modifiers with fast updates disabled
  • Expose functionality for clamping to nearest connected grid on the query interface
  • Add functionality in Unreal for clamping to any grid in a world
  • Add ability to specify usage spec to IsNavigableMulti query
  • Expose box obstacles on thread safe ORCA API
  • Height range override in IsReachable now correctly applies to query end instead of query start
  • Add log messages to polymesh pathfind when backtrack limit or max path length exceeded during search
  • Improve parallelisation of pathfinds on different worker threads when intergrid nav links are present
  • NavInvokerVolumes no longer generate nav grid outside the nav volume
  • Option on nav grid testing actors to disable the projection of the end point down to the nav grid
  • Allow stationary obstacles to move slightly before being treated as moving again
  • Fix bug generating linear auto links where vaults over small obstacles could be incorrectly ignored
  • Fix nav raycast end position height clamping
  • Fixed bug causing some raycasts to fail if start and end were in the same grid cell
  • Fix locking when checking nav grid build status when nav invokers are in use
  • Fix assert when a vehicle path is made with a slope too steep for the vehicle to decelerate on
  • Improve avoidance for slowly turning agents
  • Improvements to nav mesh generation when physical materials generate complex patterns of different nav regions
  • Fix rare crash when generating automatic nav links
  • Fixed rare NaN in context steering
  • Fix rare crash getting the trajectory for an entity
  • Do not pass inputs in the reverse direction to the Character Movement Component when decelerating to a stop
  • Don’t try to set controller rotation on vehicles
• Surface Navigation
  • Limited support for climbing agents
  • End direction for testing actors now supported
  • Fix console command mer.Grid.Draw.AgentType not working with surface agent types
  • Fixed rare infinite loop in GetBorderLines
  • Removed some asserts hit by rare geometry configurations
• 3D Navigation
  • Octree builds now produce consistent data if level geometry is unchanged, so chunk file content does not change unnecessarily
  • Ability to set end direction on MoveTo request
  • Improvements to Octree World Partition streaming performance
  • Fix cost modifiers not being shown in 3D cross section octree debug draw
  • Fix raycast through unnavigable space treating all agents as having minimum radius
  • 3D Navigation move to current location now immediately succeeds instead of immediately failing
  • Fix assert on pathfind in rare cases while octree rebuild was in progress
  • Fix nav octree being removed when a modifier is added that covers all of a disconnected part of navigable space
  • Remove warning when setting debug draw on an octree that has not been built
• Common
  • Unreal Engine 5.8 Preview support
  • Add a lightweight Unreal struct, FMercunaPath, representing Mercuna paths
  • Add nav seed component, to allow seeds to be added as components of other actors
  • Allow more methods on MerPath to be used from worker threads
  • Ability to update path end-direction explicitly and when adding a destination
  • Remove requirement for exclusive thread entry and lock when calling functions to add, remove or update modifiers
  • Deprecate the MercunaNavModifier Actor in favour of using Nav Modifier Components
  • Modifier changes no longer automatically update the nav graph in Editor, a nav graph rebuild is now required
  • Nav graph build now correctly picks up Chaos Geometry Collections in Editor
  • Fix dangling references to physical materials when physical materials are removed
  • Fix rare crash in MerEntitySystem when exiting PIE
  • Fixed exception when running with stompmalloc in MercunaMoverEditor ShutdownModule
  • Fix assert in MercunaMover when using live recompile during PIE
  • Make NavVolume robust to its nav graph being unloaded before it
  • Stop broken soft pointer causing an assert in RemoveNavVolumes
  • Make it possible to construct query filters in C++ code outside of Mercuna
  • Agent type names are now always case insensitive
  • Change method of tracking actor changes in editor to improve performance and fix nav graph being incorrectly marked dirty
  • Fixed nav volumes being allowed to rotate in world partition map when they shouldn’t
  • Fix path destination not updating if destination was changed immediately after params were updated
  • Fix shutdown crash when editor fails to start
  • Fix errors in Havok integration due to missing registration macros
  • Fix exclusion and modifier volumes not getting cleared on nav graph reset
  • Minor improvements and optimizations