negative mass

Game Engine Game Engine Support and Discussion
1

is there any way to make give objext a negative value for mass? or if not, where can i get the source code for 2.25?

oh, and also a gravity script if you have one.

2

Why would you need a negative value? That would be impossible in real life. What exactly are you trying to simulate?

3

computer simulation of an apparently reactionless drive

4

A reactionless drive? What do you mean?

5

http://www.squidsoft.net/sc/reactionless_drive_guide/

6

WOOOOOOOOOOOOOOOOOOW! :o :o :o Mind-Stimulating! WOW!!! WOOOOOOWWWW!!! OUCH! Anyway, I guess you could simulate those two properties with a constant -z propulsion, and stuff. Tricks…
Yes, but it is impossible to make a negative mass in blender.
But WOW, what amazing…stuff… :o

7

bah, I would agree with the motion actuator thing

give it a postive z value for force, and I guess set gravity to zero. That object will float. (yay)

or you could flip everything over (even the camera)

8

no, that’s not what i want.

does anybody know a gravity script?

9

MacBlender did a gravity script, but for positive gravity. Gravity.py

%<

10

not that kind of gravity. i mean i saw this script once and it was a bunch of these spheres in the game engine and they attracted this smaller sphere or whatever.

11

Setting aside the problem of negative mass, Blender could easily be hacked to allow it.

It would however not work as expected:

  1. The physics system does not simulate electrostatic charge (!)
  2. Gravity is assumed to be a force along -z.

For gravity, you just calculate the force on each body from Newton’s law of gravitation.

12 
import GameLogic

cont = GameLogic.getCurrentController()
owner = cont.getOwner()
gx = owner.gx
gy = owner.gy
gz = owner.gz

GameLogic.setGravity( [gx,gy,gz] );

##Notice##
you have to make 3 propertys.“gx,gy,gz”
gx = gravity x
gy = gravity y
gz = gravity z

13

ummm… I’ll check the python API when I get home but I don’t remember anything like that in it?! :-?

If you know the maths behind mass attraction then it should be fairly easy to work out how to do it in python.

Keith. 8)

14

that is specifically why i asked for the source code. but it seems to have misteriously dissapeared, as if it knew i would need it. i don’t suppose you know how to edit the complied version?

  1. The physics system does not simulate electrostatic charge (!)

that’s why i’m using gravity instead. and i don’t mean the built-in fall along the z-axis gravity blender has.

considering you know python.

15

The source for 2.25 is still available from CVS. However, you still need to get your hands on SOLID (the collision detection library…)