MeshPart Collision problems

[penguim2]

When importing a mesh part to be used as a system of accessible pipes in my game I’m having problems with unexpected collisions with my mesh

when trying to move into a pipe which is clearly open and also on the sides of the mesh which aren’t enclosed like the pipe.

This is what happens when the collision fidelity is set to default, in hull and box mode the collision is treated as one large block. Does anyone have any solution to overcome this problem? Ideally this would be a slide.

[Xiousa]

Roblox’s collision system doesn’t like concave shapes, as the automatic collisions are based on convex.

[Defaultio]

To better understand how Roblox handles collisions with meshparts and unions, turn on ShowDecompositionGeometry in file -> Settings -> Physics. Generally you will not get good collision fidelity in large or highly detailed shapes.

[Veldaren]

How to fix unwanted collision for MeshPart?

Roblox uses Approximate Convex Decomposition (for CSGs and MeshParts), meaning that every shape will use only convex chunks (1). It cannot create concave chunks, it can only imitate concavity by breaking the shape into mulitple convex chunks. To achieve more precise concave shape imitation you need to split the mesh at concave areas. This will allow ACD to create convex chunks at a smaller area, resulting in the collision shape being more credible to the actual mesh shape. (1) There are 3 Co…

Edit:
To add onto that, IIRC, the collision detail is measured as a percentage of a CSG/Meshpart’s complexity, meaning that the more complex a shape is, the less “focus” is applied to collisions and is instead spread across the whole shape.
So even splitting a mesh at a random spot (not necessarly at a concave area) for smaller, less complex chunks will allow ACD to focus on fewer triangles and create better collisions.

[Denis123cool5]

–bump–
there really should be a “exact” mode
it should use the same collision as the rendering
it would be laggy but a custom one would be 100x more laggy

[mothmage]

You should support (like and reply with new use cases) the feature request in the feature request category then, engineers won’t be going through support threads for requests when we have a dedicated category.

Custom terrain / roadway gripes: Add Enum.CollisionFidelity.Exact and raise the part size limit for MeshParts

As a Roblox developer, it is currently too difficult to create efficient and physically reliable terrain layouts using meshes or CSG. While Roblox’s smooth terrain system is good, it is not the answer for developers like me who are trying to create massive open world environments that span several tens of thousands of studs across. The system is simply overkill for what I need, and forcing players to load a smooth terrain level of that size would never fly. The only answer is to create terrain …