Unit of Measurement for Mass?

#1

Hello, I am trying to simulate an object colliding with another object of a particular size/weight with real world physics.
My scene is set to meters. I was wondering what is the unit of measurement for “Mass”?
For example, when applying active rigid body to an object, the default mass is “1.000”. What is this in real-world values? Is this unit of measurement in grams? Kilograms? Pounds?
Thank you!

#2

That’s actually a really good question. I couldn’t find it anywhere, but we can assume they’re using the Metric system, and my guess would be grams.

There’s not really any easy way to test this, since Maya’s built-in physics are simply for VFX and about as accurate as a worn sock. But grams would be a good place to start and then if you have to upscale or downscale, it would just be multiple of 10.

#3

The key physical attribute is gravity. The effect of mass is more in the relation to other objects, but it could affect drag with air, depending on how your simulation is set up. (without drag objects of different masses fall at the same rate… but you need to make sure the gravity is correct). So generally you don’t need to worry about units for mass. Just keep the relative masses of different objects in proportion so that collisions work correctly. For very massive objects the effect of air drag is low and for low mass objects is high, but one needs to eyeball the drag effects generally. Drag is a rather complex effect to handle just with physical units.

#4

Thanks for the response here, Duncan. That’s actually a really good and accurate way to handle mass in Maya, since gravity in real life has nothing to do with mass and everything to do with radius and density. Most will balk at this statement, given Newton’s G and his work on the topic or Einstein’s GR obviously, but note that the Earth’s gravity at sea level is 9.8 m/s² - regardless of the object falling. This alone tells us gravity isn’t about mass, but rather radius. Planetary orbits tell us the same thing. Jupiter isn’t falling towards the sun any faster than Earth would be at that distance and orbital velocity.

I’m starting to do a lot more physics simulations in Maya, not for accuracy but to demonstrate modern theories (especially regarding charge itself), and often wondered how to deal with mass at the quantum level, some billions of times smaller than Maya’s margin for error. But since it’s just relative, that shouldn’t really affect things.

#5

Einsteins theory of space/time would never work in Maya because Maya uses only one coordinate system at a time - in space and time. That would also relate to quantum physics where a particle can appear at 2 different locations at the same time. Theres no way Maya can mimic QP unless perhaps you are using a quantum computer and Autodesk paid for Duncan to take a PHD in QP :wink: Sorry just having some fun here.