Hi, i imported a very HUGE fbx file inside gg, converted the stl file to FBX inside 3ds max, work well lol but of course the object is too heavy for game-guru so when launched the level it lag, i need to test this later on gg max

The biggest issue on slow down I would think would be poly collision on the whole model, including parts that don't really need such collision on them, windows, door frames, ceilings.
If when you bring it into 3ds max and can group the objects by logical uses, like floor, walls, windows, stairs. Export each of those parts separately at the same origin, then when imported into GG you an control the collision and GG will not have to struggle so much to figure it all out.

A lot more work for you, but it will make a world of difference with in the engine when complete.

Very likely polygon collision issue. Adding this to the Fpe should make collision easier. "forcesimpleobstacle = 3"

I've been importing huge models too (poly huge rather than size) - don't have any collision issues or lag if set to box ( collisionmode = 0 ), however it does depend on the model of course whether box collision is appropriate. So likely have to do what Myke says, or have no collision at all and then add invisible boxes and planes to reproduce collision where needed separately to the model - bit tedious though if lots of rooms and fences and such. forcesimpleobstacle = 3 is for the AI to react to the object with a full poly scan.

This is the sketchfab sourced model I was testing, 1.7 million polys and 872 thousand verts.



Cheers