I have this simple domino scene where you can click a domino and apply a force to knock it. At first I had this dominoes in a scale of (x=0.1), (y=0.6), (z=0.3) 1 is supposed to be 1 meter, they fell without a problem but too slow. According to unity documentation on Rigidbody this made total sense.
Use the right size. The size of the your GameObject’s mesh is much more important than the mass of the Rigidbody. If you find that your Rigidbody is not behaving exactly how you expect - it moves slowly, floats, or doesn’t collide correctly - consider adjusting the scale of your mesh asset. Unity’s default unit scale is 1 unit = 1 meter, so the scale of your imported mesh is maintained, and applied to physics calculations. For example, a crumbling skyscraper is going to fall apart very differently than a tower made of toy blocks, so objects of different sizes should be modeled to accurate scale.
So I just re sized the dominoes to (x=0.01), (y=0.06), (z=0.03), this time they fell to the desired speed but for some reason they stop falling and don't knock the next domino.
I don't know why this is happening but i can guess that this is because at the time of calculating physics the engine doesn't waste so much resources in calculating small objects that are probably not even going to be seen by the user.
Modifying mass doesn't seem to do anything, also draw and angular draw are both 0 and already tried every collision detection mode.
Is there any solution or workaround for this?
In my experience, Unity physics doesn't like too small objects since it introduces rounding errors. A game simulation usually does not need the same accuracy as when you try to land on Mars. Therefore, I usually avoid scales less than 0.1f.
In your case, I would keep the scales at 1.0f and instead experiment with either increasing the world gravitation, changing it from the default -9.81f to -98.1f (Edit - Project Settings - Physics). Or changing the default Time Scale from 1f to 5f (Edit - Project Settings - Time).
Try not to make too big changes in the beginning since it might introduce strange effects on other parts of the gameplay.