# Collision Handling<no value>

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Due to the Addition of [SimPropContainers](modeling-simpropcontainers/) to the simulation, this page is only relevant to the legacy method of modelling scenery, ie: large-scale modelling.

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This page explains the main methods for dealing with collisions between sim objects in the simulation. Please note that this page is a general guide for handling collisions, in particular with regards to scenery elements. However you can find further information specific to aircraft from the following pages:

-   [Airframe Collision Meshes](../aircraft/airframe/airframe-collision-meshes/)
-   [Cockpit - Collision Meshes](../aircraft/cockpit/collision-meshes/)
-   [Cockpit - VR Helpers](../aircraft/cockpit/vr-helpers/)

 

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Currently only **static** (ie: Scenery) objects will detect collisions with the user aircraft

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### Simple Shape Collisions

The Microsoft Flight Simulator 2024 engine supports box, sphere and cylinder colliders. **In general we recommend using these collision shapes over mesh/material collisions for improved performance, especially in relation to scenery elements and airports.**

To place them in 3ds Max, select `Box Gizmo`, `Sphere Gizmo` or `Cylinder Gizmo` respectively:

{{< image-center
    src="images/3_Models_And_Textures/Landscape/Collision_Meshes/collision_2.png"
    alt="Collider Shapes" >}}

You would then use this tool to place the desired shape in the model, ensuring that the `Is Collider` flag from the **Parameters** window is flagged:

{{< image-center
    src="images/3_Models_And_Textures/Landscape/Collision_Meshes/collision_3.png"
    alt="Enabling Collisions In 3DS Max" >}}

 

Once you have created the shape and added it to the model, you need to link the shaped collider to the first LOD:

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This is absolutely necessary, otherwise the collider will not be exported!![Linking The Collision Shapes To LoD0](images/3_Models_And_Textures/Landscape/Collision_Meshes/collision_6.png)

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![Collision Meshes Linked To LOD0](images/3_Models_And_Textures/Landscape/Collision_Meshes/collision_7.png)Once you have completed all that, follow the export instructions given below.

 

 

### Mesh Collisions

A mesh collision involves creating an "invisible" mesh within a model that will be used as a collider when the model is placed in the simulation world. For performance and memory reasons, it is important to minimize the number of vertices in a collision mesh, so it is good practice to create a low-resolution collision mesh that wraps the high-resolution visual mesh. This essentially means that the mesh collider will be a polycrunch version of the LOD0 mesh, for example:

{{< image-center
    src="images/3_Models_And_Textures/Landscape/Collision_Meshes/collision_4.png"
    alt="Example Of A Low Poly Version Of A Scenery Object For A Collision Mesh" >}}

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There is a face count limitation of 65K triangles and a warning is displayed if it goes beyond 4096 triangles.

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Collisions will not be properly detected if the vertices are too far from each other, in particular when the object has been scaled by a large amount in the world, or it's geometry hasn't got enough subdivisions.

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Once you have created the mesh and set the material properties for it, you need to link the mesh collider to the first LOD:  

{{< image-center
    src="images/3_Models_And_Textures/Landscape/Collision_Meshes/collision_5.png"
    alt="Linkning The Mesh Collider With The LoD0." >}}

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This is absolutely necessary, otherwise the collider will not be exported!

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After doing this, you need to enable collisions with this low-poly mesh and hide it from view. For that you will first need to activate the `Collision Material` in 3DS Max, ensuring that you have set the `Material Type` to `Invisible` and enabled the material as a `Collision Material` (as shown in the image below):

{{< image-center
    src="images/3_Models_And_Textures/Landscape/Collision_Meshes/collision_1.png"
    alt="Mesh Collisions DS Max Setup" >}}

 

 

### Exporting

To export the geometry with the collision mesh it is recommended to use **Multi File Exporting**, as explained on the following page:

-   [Multi-Exporter](../../plugins/3ds-max-plugin/multi-exporter/)