ok I figured it out.
for what ever is worth, if any one has teh same issue.
It looks like the only way to assign a material to a DynamicsMeshComponent is procedurally in code.
however, the procedure is not trivial and as far as I can see it is no explained.
here are teh step I did.
-First you need to get the material and save with the Actor that will own that component.
this is what explain the existence of an UDynamicsMeshActor. one of the purpose is to just hold that material.
But it seems that the component can be assigned to any actor.
-you can create your UDynamicsMeshComponent in code (c++ or blue print)
you can assigned the material procedurally like this.
something like this.
UDynamicMesh* dynamicsMesh = NewObject<UDynamicMesh>();
{
UE::Geometry::FDynamicMesh3* const triangleMesh = dynamicsMesh->GetMeshPtr();
PolygonizeMesh mesh(triangleMesh);
ndShapeInstance box(ndShapeInstance(new ndShapeBox(100.0f, 100.0f, 100.0f)));
box.DebugShape(ndGetIdentityMatrix(), mesh);
}
SetMaterial(0, materialInstance);
SetRelativeLocation(FVector(200.0f, 200.0f, 200.0f));
SetDynamicMesh(dynamicsMesh);
NotifyMeshUpdated();
the render mesh look like this now.
This seems satisfactory for now, so unless I got something wrong, that anyone can see, this can be closed.
Julio.