69 lines
4.9 KiB
Markdown
69 lines
4.9 KiB
Markdown
# How to generate the pedestrian navigation info
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The pedestrians to walk need information about the map in a specific format. That file that describes the map for navigation is a binary file with extension `.BIN`, and they are saved in the **Nav** folder of the map. Each map needs a `.BIN` file with the same name that the map, so automatically can be loaded with the map.
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This `.BIN` file is generated from the Recast & Detour library and has all the information that allows pathfinding and crow management.
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If we need to generate this `.BIN` file for a custom map, we need to follow this process:
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* Export the map meshes
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* Rebuild the `.BIN` file with RecastBuilder
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* Copy the `.BIN` file in a `Nav/` folder with the map
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---
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## Export meshes
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We have several types of meshes for navigation. The meshes need to be identified as one of those types, using specific nomenclature.
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| Type | Start with | Description |
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| ----------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------- |
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| Ground | `Road_Sidewalk` | Pedestrians can walk over these meshes freely (sidewalks...). |
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| Grass | `Road_Crosswalk` | Pedestrians can walk over these meshes but as a second option if no ground is found. |
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| Road | `Road_Grass` | Pedestrians won't be allowed to walk on it unless we specify some percentage of pedestrians that will be allowed. |
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| Crosswalk | `Road_Road`, `Road_Curb`, `Road_Gutter`, `Road_Marking` | Pedestrians can cross the roads only through these meshes. |
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| Block | Any other name | Pedestrians will avoid these meshes always (are obstacles like traffic lights, trees, houses...). |
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<br>
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For instance, all road meshes need to start with `Road_Road` e.g: `Road_Road_Mesh_1`, `Road_Road_Mesh_2`...
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This nomenclature is used by RoadRunner when it exports the map, so we are just following the same.
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Also, we don't need to export meshes that are not of interest by the navigation system, like landscapes where pedestrians will not walk, or UE4's _sky domes_, rivers, lakes and so on.
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We can **tag** any mesh with the name **NoExport** and then the exporter will ignore that mesh.
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Once we have all meshes with the proper nomenclature and tagged the ones that we want to ignore, we can call the Carla Exporter that is found under the `File > Actors > Carla Exporter`:
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The `.OBJ` file will be saved with the name of the map with extension OBJ in the **CarlaUE4/Saved** folder of UE4.
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---
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## Rebuild the navigation binary
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With Recast & Detour library comes an executable file that needs to be used to generate the final `.BIN` file.
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The executable uses by default the parameters to work on Carla, and you only need to pass as parameter the `.OBJ` you exported above, and the `.BIN` will be created.
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You can find the executable, on the `Carla/Build/recast-{version}-install/bin/` folder, already compiled when Carla was installed.
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Run:
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```sh
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$ RecastBuilder test.object
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```
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And it will create a `test.bin` file, that needs to be copied to the map folder, inside the `Nav/` folder.
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For example, this would be the structure of files of a Test map:
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```
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Test/
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├─ Test.umap
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├─ Nav/
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│ └─ Test.bin
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└─ OpenDrive/
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└─ Test.xodr
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```
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