Mesh not created if first vertex is at origin (0,0,0) about realtimemeshcomponent

[quentincaffeino]

First: your initialization of RMC must be like this
mesh = CreateDefaultSubobject<URuntimeMeshComponent>(TEXT("GeneratedMesh"));
instead of what you have:
mesh = CreateDefaultSubobject(TEXT("GeneratedMesh"));

Let's have a look on basics of mesh generation:
Lets say you want to create a square. Then you need four vertices with coordinates: V0 (0, 0, 0); V1 (50, 0, 0); V2 (0, 50, 0); V3 (50, 50, 0)

TArray<FVector> vertices;

vertices.Add(FVector( 0,  0, 0));
vertices.Add(FVector(50,  0, 0));
vertices.Add(FVector( 0, 50, 0));
vertices.Add(FVector(50, 50, 0));

Now we need to create faces, one face requires three vertices to form a triangle. Using our square of four vertices we need to create two faces by connecting vertices in this order:

1. First triangle: V0 -> V2 -> V1
2. Second triangle: V2 -> V3 -> V1

TArray<int32> triangles;
triangles.Add(0);
triangles.Add(2);
triangles.Add(1);

triangles.Add(2);
triangles.Add(3);
triangles.Add(1);

Then we need UVs. Creating them are pretty easy. You have to calculate UV<0, 1> position for each vertex. If you want to scale texture - just multiply your UV coordinate by scale. This how it would look on our square:

TArray<FVector2D> UVs;
UVs.Add(FVector2D(0, 0));
UVs.Add(FVector2D(1, 0));
UVs.Add(FVector2D(0, 1));
UVs.Add(FVector2D(1, 1));

And finally we'll create normals and tangents. I prefer generating them using KismetProceduralMeshLibrary function: LINK.

Also have a look at RuntimeMeshComponent wiki

I hope I helped you. Sorry for my English.

[Koderz]

I've not seen any problem like this in any of my tests. It appears to me that the vertex winding order got reversed on your first example and so backface cull kicked in and kept it from rendering.

I'm gonna go ahead and close this as I haven't heard anything else from you in a while. If you still see this or any other issue feel free to reopen or post a new issue!

Thanks!