Dynamics and gravity

[randomizer]

am i right that an object in the real world will fall one meter in the first second?
why does an object in maya with a gravity field connected to it doesn't do the same?
i created a sphere and raised it to 100 units because the world setting in maya is cm. i had to raise the magnitude of the gravity field to 217 to have the sphere fall all the 100 cm in 25 frames.

most dynamic simulations i see look kinda slow motion.

so is anyone here who can tell me how to achieve real world gravity in maya?

[alphajoe]

I know this is an ancient post, but there was never a response to it and I have the same question myself. After creating a simulation, such as a basic sphere falling onto a plane, it is like the sphere is falling through water or something. It just seems to be going very slow. And I am not talking about playing in the maya interface, but playblasts and renders as well. Once the scene is rendered the motion just seems slow.

[joojaa]

OKay fisrt unlearn aeverything you know of dimensions, and ill light on whats going on.

In the real world the accelereation of a object that falls is 9.81 m/s^2 (or well it varies a but depending on whare on earth you are) wich means that if you integrate accelareation over time to time you get for one second of falling 1/2*9.81*1^2 wich is about 5 meters.

NOW for the thing about maya and units. Well it so happens that maya is unitless! sure the prefs say its a cm, but theres absolutely no other clue about this (actualy deleting the entire pref item would sort the probem better than fixing the scale /praticle expression problem). IN fact you are better of FOREGTTING you ever saw that ever, because maya reacts very badly to changing the setting.

(im not getting into it but before you guys start tellling me im insane ill just say to you UNITS dont matter only their relation does, because in maya you dont have realworld reltions it does not realy matter if you wthink of 1 unit as meter or kilometer or one umpalumpa as long as you yourself keep track of what it is)

Now in the default configuration maya dynamics is calibrated to 1 unit is equal to 1 meter despite what you might think from looking at the prefs. So the force magnitudes realwordl counterrpart unit is Kg*yourImaginedUnit/second^2 now if you wanted your world to be cm as in your prefs. youd need a magnitude of 981 to pull it off right.

[joojaa]

OKay first unlearn everything you know of dimensions, and ill light on whats going on.

In the real world the accelereation of a object that falls is 9.81 m/s^2 (or well it varies a but depending on where on earth you are) wich means that if you integrate accelareation over time to time you get for one second of falling 1/2*9.81*1^2 wich is about 5 meters.

NOW for the thing about maya and units. Well it so happens that maya is unitless! sure the prefs say its a cm, but theres absolutely no other clue about this (actualy deleting the entire pref item would sort the probem better than fixing the scale /praticle expression problem). IN fact you are better of FOREGTTING you ever saw that ever, because maya reacts very badly to changing the setting.

(im not getting into it but before you guys start tellling me im insane ill just say to you UNITS dont matter only their relation does, because in maya you dont have realworld reltions it does not realy matter if you think of 1 unit as meter or kilometer or one umpalumpa as long as you yourself keep track of what it is)

Now in the default configuration maya dynamics is calibrated to 1 unit is equal to 1 meter despite what you might think from looking at the prefs. So the force magnitudes realwordl counterrpart unit is yourimaginedWeightUnit*yourImaginedUnit/second^2 (your imagined weightunit is offcourse kg if you choose any si unit as your base) now if you wanted your world to be cm as in your prefs. youd need a magnitude of 981 to pull it off right.

[morourke]

a few years ago (I believe it was 2003 -- whatever version of Maya that was) I was preparing a workshop on dynamics. I had seen that, as the first poster says, everthing seemed to move very slowly. I also had changed gravity to 981 and it still didn't seem to give physically accurate results. so I called the support people at AliasWavefront to ask whether Maya dynamicis did its calculations accurately according to the units you used. the answer then was, "well, no not really." that was a few versions ago, but it seems to still be the case.

if you've got a simulation that looks good in every respect except that it is too slow, you can speed things up by keyframing the Current Time attribute in the rigid Solver node.

also, be aware that when you do cloth dynamics in Maya, the dimensions of your cloth objects DO matter.

[joojaa]

You havent have happened to change your gflobal unit to something eelse from the dafeulat cm because if you do maya will go totaly bonkers in the dynamics department.

981 is offcourse only correct if you asume 1 unit is a cm! if you asume 1 unit is millimeter it need to be 9810 and so on.

But if you asume 1 unit is cm then it moves exactly lkike it should whan set to 981... trust me i measurted it (its been like that since the beginning of maya dynamics when i started in maya 1.5). By the way it has allways behaved like this and correctly. what world do you guys live in if your gravity works faster? or rather what unit do you work in.

Also the cloth objects have a dimension multipler to tell what the global unit is so the solver knows your global scale! if you havent nothiced. But yeah cloth is byy default set to the 1 unit is meter magnitude too just like dynamics.

Point is that default maya setting is 1 unit equals to 1 meter wich means that if you think 1 unit is cm like the prefs say your actulay going to get a asolution thats 100/th sloower than you expect.

Edity... now if you compare this time to something in reality dripping like dropping a pen to the floor, bear in mind that a bit demepnidng on how you keep the pen in your hand whan you let t go., you might have by accident given it a 0.1 seconds worth of acceleration before ytou dorp it. this might not seem much but it will cut the drop time on short distances quite a bit.