Physics Simulation Forum

I just started playing abround with bullet and found the following, which is the same for the gravity force in maya.

Scene settings = centimeter and 24 frames per second

acceleration pattern:

1 sec 24 frames = 4.52 units

2 sec 24 frames = 14.312 units

3 sec 24 frames = 24.112 units

4 sec 24 frames = 33.912 units

5 sec 24 frames = 42.711 units

6 sec 24 frames = 53.511 units

7 sec 24 frames = 63.311 units

8 sec 24 frames = 73.111 units

9 sec 24 frames = 82.911 units

10 sec 24 frames = 92.711 units

276 sec 24 frames = 355.672 units

277 sec 24 frames = 365.472 units

Mass does not change the acceleration pattern.

The acceleration does not reach a terminal velocity.

Your RBD object will fall the same amount of units regardless of your units being set to centimeters or meters ( so if your units are set to centimeters it falls 4.5 cm the first 24 frames and if your units are set to meters then it falls 4.5 m the first 24 frames)

Which meants you have to work either in meters with you gravity set to default -9.8 or your scene set to cenitimeters with your gravity set to -980

I also find the only way to make an object fall 9.8 units the first second is to turn the gravity to -21.3 or with your scene set to centimeters have gravity turned to -2130 to fall 9.8 meters the first second.

Any explanation would be much appreciated.
And does anyone know how to make gravity work as real world in maya and what scene scale etc. is best to work with?

That's 9.8 metres per second per second - it's an acceleration. So after 1 second, your object should be travelling at 9.8m/s, but it won't have been at that velocity for the whole of the first second, and the distance travelled will be less than that. To get it to fall 9.8 metres in 1 second, you'll have to bump up the gravity, which is what you've found, and is correct.

From your post, it looks like you are looking at a starting frame of 1 and ending frame of 24. This is actually 23 frames and is short 1 frame of a second.
An object falls 4.9 meters in the first second. If you look at the 25 frame (24 frames of falling), you'll see a distance of 4.818 units. Much closer to real world (but still not perfect). Close enough. So one unit can be treated as a meter (even thought maya says it's centimeters).