Hi. I am making some 3D models with some version of 3D Studio but i have no idea how big to make my models. Should they cover all of the grid or a few sections on it? Please help. thanks

It doesn't matter, you can just rescale them later to fit whatever coordinate system they're supposed to be used in. Just make them so they look good when they cover the area of the screen they're supposed to cover.

You only nead to deside what units your using.

1 unit == 1 mm
(good for modeling small objects ie. insides of computer)

1 unit == 1 meter
(good for modeling human enviroments ie. human == 1.8m)

1 unit == 1 km
(good for modeling space games c == 300 000km / s)

/ Tyrian

Ps. don`t model with out scale (it`s true pain to rescale 100++ game objects)

I would do both suggestions... Try to model to scale, but then make sure you have one thing with real world scale that you can scale everything else to. For example, if you know that a character is 6 feet tall, scale that character to be 6 feet tall in whatever modeling program you're using. Then bring in other objects and scale them to fit that character if needed.

It's really not that big of a pain to do some scale checking... I wouldn't go 100% with just trying to model everything to scale and not comparing anything. Also there are just things you're going to model that don't really have real world measurements. (cartoony distorted stuff, fantasy objects/creatures, etc) You just have to resize this stuff by eye.

What I'm doing for my 2D game is just modeling everything in relation to the size of one tile. I have a simple block that I can import into any scene that's one tile in size, and I model things in relation to that object.

For 3D modeling I would say that it would be a mistake not to model things to scale. In 3D Studio you can customize your interface to change measurements to what you would like, but the bottom line is that it is just good practice to model things to scale. Imagine working for a team where everyone's objects are different sizes, sounds like a pain to me. Plus, if you are doing characters, you can run into a lot of problems trying to scale if you have already rigged your character.