opengl - What is the norm for positioning models in model space? -

are models centered @ origin, or there bottom @ origin, or else?

i ask because in app have store world positions of objects, , i'm not sure if position should designate center, bottom center, or else. match how it's done in model space makes transformations easier.

what standard?

there no standard centering model @ origin convenient way things; easier define bounding volumes way primitives have simpler formulas defining them.

unless there problem models have i'd set position of model space origin world space position easiest way go , works ok in cases.