3D prospective question

I have been trying to find the answer to this question for some time.
If an object appears to be 1 meter wide at say 1 meter away, how far away would it have to be to appear 1/2 meter wide. Or 1/4 meter wide.
At what rate does an object appear smaller as it moves farther away from the camera.
I hope you understand my question.

I need to know this so I can calculate the ideal distance from the camera a mesh can be used with half the poly count.
And then 1/4 the poly count, etc..

I'm pretty sure that if you double the distance, you halve the size.

So at 2 meters, it would be 1/2 meter wide, and at 4 meters, it would be 1/4 meter wide.

In other words, size = 1 / distance,
or in this case, distance = 1 / size.

And it's perspective, not propsective. :-)

It depends what FOV you have etc, so there is NO hard rules about LOD sizing... try FOV=1 deg and object is pretty much the same sized no matter how far it is. :)

Thanks sswift. That seems to be the scale used by blitz3D too.
From measureing objects on screen at different units away that's what I get.