Moving from Newton 4

[SpiderPig523]

Hey everyone, I've currently got newton 4 in my game engine but am thinking about using Jolt instead and have a few questions before I do. My game has lots of small planets that all influence one another.

1. Is the player controller robust enough to work with multiple gravity sources?
2. Can physics operate locally per planet as the planet orbits and moves through the world? E.g. two planets spin about there axis and orbit each other as well as the sun. Each planet can be walked on and the player can interact with physics objects on their surface. Newton could kind of do this but surface objects would never sleep and would jitter a lot.
3. Can static physics tiles be created on the fly for terrain? E.g. I have voxel terrain and what I've been doing is when physics objects get close to the surface I create a static physics object at that location to represent the surface under that object and then delete it as the object moves away.

Can jolt do these things you think? Thanks for any insight! Much appreciated!

[jrouwe]

Is the player controller robust enough to work with multiple gravity sources?

The character controller doesn't know about gravity (it's a kinematic-like construct). You must apply it yourself, so yes this should work.

Can physics operate locally per planet as the planet orbits and moves through the world? E.g. two planets spin about there axis and orbit each other as well as the sun. Each planet can be walked on and the player can interact with physics objects on their surface. Newton could kind of do this but surface objects would never sleep and would jitter a lot.

I think you would have to create a PhysicsSystem per planet if you want objects to sleep. Otherwise it would probably work similar to Newton (can't tell if it would jitter). Doing this would add a lot of complexity on your side as you need objects that move between planets to move between PhysicsSystems. I don't know what the scale of your universe is, but if it is big then I think you need to work with multiple PhysicsSystems anyway.

Note that there is a (small) section on space sims in the docs: https://jrouwe.github.io/JoltPhysics/#space-simulations

Can static physics tiles be created on the fly for terrain? E.g. I have voxel terrain and what I've been doing is when physics objects get close to the surface I create a static physics object at that location to represent the surface under that object and then delete it as the object moves away.

Yes, that should work.

Note that there is a simple 'planet demo' here: https://github.com/jrouwe/JoltPhysics/blob/master/Samples/Tests/Character/CharacterPlanetTest.cpp and there is an example of a character on a fast moving ship here: https://github.com/jrouwe/JoltPhysics/blob/master/Samples/Tests/Character/CharacterSpaceShipTest.cpp

[SpiderPig523]

Cool, thanks. How does jolt go with fast moving objects? Like meteor speed objects colliding with the terrain? I had made my own system for this before that didn't use the physics system, but curious if it would work with jolt.

[jrouwe]

If you use motion quality LinearCast then they should at least not tunnel through the terrain, but even if you use double precision simulation, the velocities will be tracked as single precision floats. So, for sufficiently high speeds it will eventually fail. So I can't say if it will work for you or not.

[SpiderPig523]

Yeah that's okay. It sounds like I can make it work either way. Thanks for your time.