Mesh memory usage much higher than it should be

[sebj]

I am looking at the Memory Profiler in the Editor and notice that the of Meshes is considerably larger than it should be, by a factor of 3x.
This is based on our own estimates, and the report of the vertices/indices in the Inspector.

E.g.

Here are a set of meshes sampled from our application at runtime:

The Estimated Size is calculated as:

Vertices * 2 * 12 + Vertices * UVChannels * 8 + Triangles * 3 * 2

(I have verified in the Inspector that the meshes contain Positions and Normals, and the UV Channels, and nothing else).

This appears to be the case when loading meshes from AssetBundles, and when creating them procedurally.
I have tried to clear the isReadable flag by calling Mesh.UploadMeshData(true), but it doesn’t make a difference.

var m = go.GetComponentInChildren<MeshFilter>().sharedMesh;
if(m.isReadable)
{
    m.UploadMeshData(true);
}

It also doesn’t appear to be an Editor specific issue as I see similar trends in terms of estimated loaded mesh size vs used unmanaged memory in WebGL builds.

Why are these meshes taking so much memory?

(Some similar threads that were never resolved:

Mesh Memory Usage

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Inefficient Mesh Memory Allocation

As I have done some research and profiling, I realized that Unity is allocating a lot of memory for meshes. It seems to allocate up to 4x what I would expect. Meshes should just contain the vertex, color, and uv data, if I understand correctly, so I'm not sure why Unity allocates a lot more than what is required for that. I'm currently being forced to write my game in Unity, but then write the procedural generation and even mesh rendering in native code as part of a plugin (using Metal and Ope…

Meshes using way more data than expected / calculated )

[Kurt-Dekker]

@sebj

Why are these meshes taking so much memory?

@sebj

(Some similar threads that were never resolved:

They’re not going to get answered.

A mesh structure in memory in a high performance game engine may be laid out in a way that consumes more (or less) memory than naively multiplying out the components.

That’s why you will not find something in the docs saying “Here is how to compute how much RAM our engine will use for your mesh.”

Odds are it is different on every platform anyway, such as on Mac, PC, iOS, Android, WebGL, Switch and XBox and Playstation.