cocos2d for iPhone

A fast, easy to use, free, and community supported 2D game engine

1. 

   jackiedigital
   Member

   Hi all,

   I'm working on implementation of "pressure region" for my game.

   What I want to achieve is when my object (ball) make contact with my pressure region to be able to apply impulse of appropriate strength. And that "appropriate strength impulse" is my problem.

   I want that my redBall which is closer to center of pressure region have higher impulse than blueBall that is further from pressure source.

   I think this problem is less complex than explosion simulation, because i can apply force to the center of ball, doesn't need rotation..

   Maybe I can do it with just b2Distance function...?

   Posted 2 years ago #
2. 

   Lam
   Member

   Is it pretty much like reversing gravitational force?

   If so you can use a simplified formula of force Fp = m1*m2/r^2

   So you find the distance between the object and the pressure region center 'r'.

   You know the mass of one = m1. The other can be the pressure = m2.

   The next thing is to find the vector of direction to apply that force.

   Since a vector d = tip - tail. Just make sure you have a normalized vector whose tail = the 'pressure region center' and the tip = 'object position'.

   Now you can apply that force with force = |d|*Fp

   Posted 2 years ago #
3. 

   Jeston
   Member

   Well,

   It sounds like a bouyancy force calculation is the situation your in, without surface flow and drag, pressure is defined as the Force per surface area.

   The ideal gas law being P = nRT / V. Removing temperature as a constant along with the gas constant R: Pressure becomes a function of n/T.

   In simpler terms, the pressure of a submerged object is only a function of depth. So if you consider the deepest part of your region with the maximum force, then Pressure is a function of how close to the center it is.

   Specifically submerged fluid pressure is:
   P = density * gravity * depth

   Posted 2 years ago #
4. 

   Lam
   Member

   @Jeston
   That makes more sense. I like it :)

   Then the total force would be your fluid pressure 'P' acting against the objects force of gravity.

   It would look pretty cool with the 'bobbing' effect until the forces balance out.

   That's pretty silly of me for not thinking of buoyancy...

   Posted 2 years ago #
5. 

   jackiedigital
   Member

   Thank you all for quick responses.

   Basically, I can make my pressure region of polygons which represent depth, so when I want to apply pressure on ball I can take that depth value of polygon to calculate pressure to apply. Also density of balls and gravity of the world are always same.

   Posted 2 years ago #
6. 

   Jeston
   Member

   I wanted to add a slight change to my response, I didn't want to confuse the concept of fluid pressure and the idea of a bouyancy force...

   While I recommended that you use & calculate a bouyancy force, the equations I had listed apply to the pressure forces which was what was asked.

   I wanted to clarify that depth has no effect on an object's bouyancy force in simplistic systems: ie: ignoring compression, etc...

   A bouyancy force is relational to the weight of the displaced volume of air / fluid.

   At least I am pretty sure :)
   ~J

   Posted 2 years ago #

RSS feed for this topic

Reply

You must log in to post.