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Hieronder wat 'bevindingen' en vragen vanaf het punt waar ik vast loop.
Omdat ik dit verhaal ook op t autodesk-forum heb gezet is t in het engels, maar wellicht hebben mensen hier op het 'thuishonk' er ook gedachten over:
I want to set up a spherical force-field. In the real world: F= G*M/R^2
There are only 2 parameters; Strength and Decay.
So it seemed logical to think F= A*Strength /R^(B*Decay) with A and B some constant.
For testing I set up a scene with a particle in (0,0,0) and the Gravity Space Warp at (R,0,0). Units in meters, frame-rate at 25/s.
With Decay = 0 and a sufficient big R.
(With no Decay, R is irrelevant as long as the particle doesnt reach the spacewarp.)
I found X(t)= 72* Strength* (t^2 +- t/25)
The +-t/25 part is not a start-velocity as you might expect.
In the non-linear regression tool i used, when i use frame 25,50,75 etc as hole seconds, i get +t/25.
With frame 24,49,74 etc as seconds i get -t/25..... so, something with half a frame of,
After a few seconds the effect is very small. fair enough.
The physical meaning of a default acceleration of 144 m/s2 is unclear. (about half the gravity at the surface of the Sun) Maybe because astrophysical events are very slow and animations of it are mostly time-compressed.
On to the effect of Decay;
I made several attempts with different setups; but it turns out to lead to very very complicated formulas with no obvious connection of the parameters. It seems different Rs and Strengths lead to different interpretations of Decay.
Even more pragmatic approaches failed. For instance:
If we were to make a scene where it takes a particle 1000 frames to reach the gravity-object.
In a inverse-quadratic force-field it would take the particle 818 frames to reach halfway.
Setting this up proved very hard, but i found a configuration meeting above criteria.
However, closer inspection of the path over time indicated the acceleration was still not inverse-quadratic with distance.
Whats-more; Doubling Strength should lead to the particle reaching target in 1/sqrt[2]=0.707 times the frames, and halfway should still be at 81.8% (frame 578). Neither was true.
Since Ive put in over 16 hours figuring this out, i think it is time to call in some help.
Most pragmatic question:
-At which decay/strength combination is the force field inverse-quadratic with distance?
and because im somewhat autistic when it comes to math:
- Whats the general formula connecting these 3 parameters with the force field?
Kind regards and Heeelp,
Ralf Bartsch
Ik ga er van uit dat je dit ook in hebt gesteld, en ik ga er ook van uit dat er een interpretatie fout zit in 3ds max, maar heb je je system units ook op meters gezet? Alleen je units op meters zetten blijft 3dsmax in inches rekenen.
12 jaar geleden
alles staat op meters. maar ik denk niet dat t meer als een constante in de vergelijking uit zou maken.
12 jaar geleden
Jep, daar heb je gelijk in, just in kees 😉
12 jaar geleden
ieder idee is welkom hoor.
12 jaar geleden