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A navigation mesh describes the traversable safe area for an agent with its center position at zero radius. If you want pathfinding to account for an agent's (collision) size you need to shrink the navigation mesh accordingly.
Navigation works independent from other engine parts like rendering and physics. A navigation mesh is the data format to exchange information from those other systems as it describes the traversable safe area for a specific agent. All the necessary information from other engine parts need to be already factored in when creating a navigation mesh. E.g. like visuals that an agent should not clip through or physics collision shapes that an agent should not collide with. This process of factoring in all those wanted navigation restrictions from other engine parts like visuals and collision is commonly called navigation mesh baking.
If you experience clipping or collision problems while following navigation paths always remember that you need to tell the navigation system through an appropriated navigation mesh what your intentions are. By itself the navigation system will never know "this is a tree / rock / wall collision shape or visual mesh" because it only knows "here I was told I can path safely cause it is on navigation mesh".
Creating 2D NavigationMeshes¶
Navigation meshes in the 2D editor are created with the help of the NavigationPolygon draw tools that appear in the top bar of the editor when a NavigationRegion2D is selected.
The NavigationPolygon draw tools can be used to create and edit navigation meshes by defining
The outline polygons are later converted to real NavigationMesh resources for the NavigationServer regions.
Multiple outlines can be added to the same NavPolygon resource as long as they do not intersect or overlap. Each additional outline will cut a hole in the polygon created by the larger outline. If the larger polygon is already a hole it will create a new navigation mesh polygon inside.
Outlines are not a replacement if the intention is to merge aligned polygons e.g. from grid cells. Outlines, as the name would suggest, cannot intersect each other or have any overlapping vertex positions.
Outline layouts like seen in this picture will fail the convex partitioning required by the navigation mesh generation. In this layout cases the outline tool cannot be used. Use the Geometry2D class for polygon merge or intersect operations to create a valid merged mesh for navigation.
The NavigationServer does not connect navigation mesh islands from the same NavigationMesh resource. Do not create multiple disconnected islands in the same NavigationRegion2D and NavPoly resource if they should be later connected.
For 2D no similar navigation mesh baking with geometry parsing exists like in 3D. The Geometry2D class functions for offset, merge, intersect and clip can be used to shrink or enlarge existing NavigationPolygons to different actor sizes.
Creating 3D NavigationMeshes¶
Navigation meshes in the 3D editor are created with the help of the NavigationMeshGenerator singleton and the NavigationMesh bake settings that appear in the editor inspector.
NavigationMesh baking is the process of creating a simplified mesh used for pathfinding out of (complex) 3D level geometry. For this process Godot parses scene geometry and hands the raw mesh or collision data to the third-party ReCast library for processing and creation of the final navigationmesh.
The resulting NavigationMesh is an approximation of the source geometry surfaces for both performance and technical reasons. Do not expect the NavigationMesh to perfectly follow the original surfaces. Especially navigation polygons placed over ramps will not keep an equal distance to the ground surface. To align an actor perfectly with the ground use other means like