Physics and Blender's Measurements?????????

Game Engine Game Engine Support and Discussion
1

I’ve been using Blender since it first arrived to the public, but there’s been one thing that I’ve always had trouble with. I used the Blender Gamekit and it says that:

gravity default-9.80 (v. 2.36)
1 blender unit = 1meter
1 grid unit = 0.05 / blender unit, which means every 20 grid squares is a meter

I’m from the US, so I naturally think in feet and inches instead of meters. The manual says you can easily calculate to adjust the gravity setting to accomidate this. I’ve done several calculations using different equations, but have yet to find one that seems acurate.

using the info above, I’ve used this equation:

N C
____ = ____
9.80 1meter = G

   20

C = the desired unit you want, converted to meters
N = the gravity setting for 20 grid sqaures
G = the gravity setting to use to make 1 new unit equal to 1 grid square

Using this calculation to make 1 grid square = 1 foot, the gravity seems to be that of the moon, even without general air damping. Objects fall at a very slow rate.

I tried another equation that I can’t remember now, but I came up with a gravity setting that is something like 6.09 something… This calculation seemed to be more acurate when trying to convert 1 grid square to 1 foot. But again, for the project I’m currently on, I would like exact or close to exact physics calculations.

So, my question is, to anybody who can answer it, how does Blender’s physics equivilate to real-world physics (i.e. gravity @ 6.09 = ?)??? How does the grid squares, the mass, the damping, the gravity, etc.??? I have looked and looked, but am not able to find this answer anywhere. If you need real-world physics, but simply adjust until it looks about right, you can’t trust your answers to be accurate. If you honestly know the answers to my question, please tell.

Thank you, and happy blending!
,Jared C. Matthews :wink:

2

i looked back at the equation i wrote and realized that the N and C are sitting right next to each other. the N is over the first ratio and the C over the second.

3

I don’t know where you get the “.05” ratio. As far as I can tell Blender’s default units are meters. (Grid lines may be spaced differently depending on your zoom level and grid settings.) To see the location of objects in Blender units, press the “n” key.

Earth Gravity is 9.8 meters-per-second-per-second (m/s/s) at the surface. It’s easy to convert that to 32 feet-per-second-per-second because the time units (seconds) are the same.

Gravity = G x S

where G is based on the units you use (9.8 for meters, 32 for feet) and S is the scale. If you model using metric measurement at 10:1 scale, then gravity should be 98. If you model in feet at 1:10 scale then gravity should be 3.2.