3D Physics Engine Demo in Java
Turn captions on please !
I have written this physics engine in java using opengl for the rendering, here are the results.
Main features:
*Arbitrary static geometry and infinite worlds
*Rigid bodies can be made up of several arbitrary convex hulls built on the fly from input vertices / spheres / capsules (not shown in the video)
*Several constraint types: spring, rope, weld, rotation & translation axis, angular & linear motors, wheels.
*I took great care to reduce the memory footprint as much as possible and keep the garbage collector happy :) (the contacts are cached and reused, no memory allocation unless new contacts are created)
How it works:
My main source of information was that page: https://box2d.org/downloads/
You can learn everything there, even though it's in 2D. That mean you will have to work a bit more to adapt the concepts to 3D ;)
I used the following algorithms / data structures:
*Broad phase:
-grid & octrees to retreive the relevant triangles of the static geometry
-bounding volume hierarchy of AABBs (aligned axis bounding boxes) for the body vs body contacts.
*Contact creation:
-Separating axis theorem (SAT) for convex hull vs convex hull
-GJK for sphere / capsule vs convex hull
*Constraint solver:
-sequential impulse solver: impulses are applied sequentialy until the constraints are satisfied or a fixed number of iteration is reached. That means that performance is tightly bound with the quality of the simulation since more iterations will enable more accurate results.
*Time stepping scheme:
-Semi-implict Euler integration for velocity and rotation.
-Implicit Euler integration for rotation when gyroscopic movement is enabled.
Known limitations:
*Warm starting isn't implemented yet, that is why there is some jittering and some objects can take a while before going into sleep mode.
*No time of impact solver, fast moving objects can tunnel through walls.
*No parallelism: the algorithm is single-core only.
*Some bugs can happen during the contact creation phase which lead to incoherent contact points.
That's all, I hope you like it :)