phisical forces... (emulating the reality) VR ENGINE FOR MSX!!!!!!

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Door flyguille

Prophet (3028)

afbeelding van flyguille

18-10-2004, 19:00

i am diagramming a VR engine for a proyect that i starts and i want to knows some things about...

how to calculate:

The exact "impact energy" spended on the crash of two objects taking in account the forces kinetics , forces centrifugal, wheight of the object...

on the same things... how to calculate the deviation of trajectories of the different objects...

i have some ideas but i cant figure out how to mix the kinetics/centrifugal forces values. And less, how to taking in account the difference of weight of the 2 objects.

I also have problems in calculating the elevation correctly from an object according to the atmospheric friction, energy reduction that loads the object.... and if the same one falls to the water, how to calculating the flotation according to the mass / volume of the object and the ascent speed..

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Van flyguille

Prophet (3028)

afbeelding van flyguille

18-10-2004, 19:42

come on.... nobody is a phisician?

Van anonymous

incognito ergo sum (116)

afbeelding van anonymous

18-10-2004, 19:58

You mean a physisist... A physician is a doctor!
If someone knows it they will write it, but by impatiently asking like this the chance someone who knows will take the trouble is getting lower.

Van Thom

Paladin (691)

afbeelding van Thom

18-10-2004, 21:24

Well, I am a physicist. I've done quite some modelling as well (ocean currents).
However, I'm afraid you're utterly over-ambitious. Unless you make some heavy simplifications even simple classical mechanics will need loads of processing power which MSX does not have. Don't even think about friction. That's nonlinear stuff.

Still, you might use simple things like conservation of momentum.

The exact "impact energy" spended on the crash of two objects taking in account the forces kinetics , forces centrifugal, wheight of the object...
This confuses me a lot. What do you mean by "forces kinetics"?

If one denotes the total force by F, F is just the sum of all forces on the object (like centrifugal, coriolis forces, friction and gravity.)

Van flyguille

Prophet (3028)

afbeelding van flyguille

18-10-2004, 21:35

i want to calculate the force spend in the impact to calculate the possible damage caused to the object...

i want to be simplist, so i have all precalc funtion SIN/COS, and fast multiplication/ div function in assembler....

firsts all object will be treated as spheres....

i have the current speed, wheight, mass, trayectory, of each object....

now, when 2 objects impacts.... i want an acuracy calculation of the impact force , to calculate the damage of the objects.... but also that depends of the weight of each object ....

how are the general purpose formulas?

Van Thom

Paladin (691)

afbeelding van Thom

18-10-2004, 22:37

but also that depends of the weight of each object ....
Not only the weight. You also need to know what each object is made of (matter) and how that type of matter responds to an impact. Intricate stuff.

Let's forget about impact and focus on dynamics only for now.

Conservation of momentum

A ------> <---------- B

Suppose we have two objects moving in 1 dimension (along an x-axis). Object A has a weight m1 and velocity v1. B has a weight m2 and velocity v2.

The momentum of A is now given by p1 = m1 * v1.
The momentum of B is equal to p2 = m2 * v2.

The law of conservation of momentum states that p1 + p2 before impact is equal to p1 + p2 after impact.

p1 + p2 = p3 + p4 (p3 = momentum of A after impact, p4 = momentum of B after impact).

This way you're able to calculate the velocities after a collision.
However, when damage occurs momentum will get lost and hence this law isn't valid (it's only valid when all momentum is exchanged after the collision)

Van flyguille

Prophet (3028)

afbeelding van flyguille

18-10-2004, 22:58

i understand that, it is very simplist because that is 1 dimension.... but is a start.

now, thinking in a pool-table game by example.

where all objects ofcourse are balls....

you has 2 dimensions.....

when one ball runs and then it crashs with another ball...

now, the two balls gets differents directions and speeds...., here we knows how to calculate the speed resultant only when the ball crashes with the other fully in its center... what happens when the ball impact in a side , how to calculate the trayectories resultants?, and about the speeds, how that affects the speeds.... because if only crash in a side the lose of forces are not completes.... i guests

Van Thom

Paladin (691)

afbeelding van Thom

18-10-2004, 23:17

It's no problem at all to expand the above to 2 or 3 dimensions. The only difference is that p1 and p2 are now vectors (well, the velocities are and thus the momentum as momentum = weigth times velocity.)

For instance, p1 = m1 * (u1, v1)
where m1 is the mass, u1 the velocity parallel to the x-axis and v1 the velocity parallel to the y-axis (the speed is then given by SQRT(u1*u1 + v1*v2).)

p1 + p2 = p3 + p4 then leads to an extra equation:

m1 * u1 + m2 * u2 = m1 * u3 + m2 * u4
m1 * v1 + m2 * v2 = m1 * v3 + m2 * v4
(note that m1 and m2 do not change after a collision while playing pool, those values are fixed. In particle physics it would be possible though.)

Van Thom

Paladin (691)

afbeelding van Thom

18-10-2004, 23:24

And as you usually only knows the speed of a ball you need to calculate it's 2 components u and v relative to a base (normally your base is just a simple x-y plane).

Example.
A ball travels with 1 m/s and it's direction is 30 degrees anti-clockwise.

y    velocity vector
|   /
|  /
| /
|/  \ 30 degrees
---------- x

Hence its x component (u) equals speed times cosine (30 degrees) and its y component (v) equals speed times sine (30 degrees).

Van flyguille

Prophet (3028)

afbeelding van flyguille

18-10-2004, 23:43

And as you usually only knows the speed of a ball you need to calculate it's 2 components u and v relative to a base (normally your base is just a simple x-y plane).

Example.
A ball travels with 1 m/s and it's direction is 30 degrees anti-clockwise.

y    velocity vector
|   /
|  /
| /
|/  \ 30 degrees
---------- x

Hence its x component (u) equals speed times cosine (30 degrees) and its y component (v) equals speed times sine (30 degrees).

from this example i not figure out how to calculate the corrects directions taken according with

if the balls craches fully ... by its centers.....

or if the balls crashes by a side or just touches a bit.....

Van flyguille

Prophet (3028)

afbeelding van flyguille

18-10-2004, 23:50

For instance, p1 = m1 * (u1, v1)
where m1 is the mass, u1 the velocity parallel to the x-axis and v1 the velocity parallel to the y-axis (the speed is then given by SQRT(u1*u1 + v1*v2).)

is it correctly or you means SQRT(u1*u2 + v1*v2) ?

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