Physics simulation without appstates
The BulletAppState class
provides a convenient interface
for configuring, accessing, updating, and debugging
a PhysicsSpace.
However, if an application doesn’t require debug visualization, it can instantiate a physics space directly and update it explicitly.
HelloUpdate is a simple application that demonstrates direct instantiation and explicit updating.
Furthermore, an application running in a headless environment (such as a server) might not even need a scene graph. By instantiating collision objects directly (not using physics controls), you can simulate physics without a scene graph.
And by using NativeLibraryLoader to explicitly load the native library,
such applications can completely avoid initializing JMonkeyEngine.
HelloConsole is a console application that demonstrates explicitly loading the native library.
For applications without a scene graph, consider using Libbulletjme instead of Minie.
Constructors
Both examples used the simplest PhysicsSpace
constructor, which is fine for most applications.
However there are actually different 8 ways
to directly instantiate a physics space:
PhysicsSpace space1 = new PhysicsSpace(worldMin, worldMax, broadphase, solver);
PhysicsSpace space2 = new PhysicsSpace(worldMin, worldMax, broadphase);
PhysicsSpace space3 = new PhysicsSpace(worldMin, worldMax);
PhysicsSpace space4 = new PhysicsSpace(broadphase);
PhysicsSpace space5 = new PhysicsSoftSpace(worldMin, worldMax, broadphase);
PhysicsSpace space6
= new MultiBodySpace(worldMin, worldMax, broadphase, solverType);
PhysicsSpace space7 = new MultiBodySpace(worldMin, worldMax, broadphase);
PhysicsSpace space8 = new PhysicsSoftSpace(broadphase);The first 4 constructors can be used
only if soft bodies and multibodies will not be added to the space.
Construct a PhysicsSoftSpace
to enable soft-body physics.
Construct a MultiBodySpace
to enable multi-body physics.
For broadphase and solver, stick with DBVT and SI respectively,
unless you understand what you’re doing.
The world bounds are used only by
the sweep-and-prune broadphase accelerators
(AXIS_SWEEP_3 and AXIS_SWEEP_3_32).
The SIMPLE and DBVT accelerators ignore them.
|
Defaults
If the solver argument is omitted, then a
Sequential Impulse (SI) solver
will be used.
If the broadphase argument is omitted,
then the incremental 3-D sweep-and-prune
(AXIS_SWEEP_3) broadphase accelerator will be used.
If broadphase is AXIS_SWEEP_3 or AXIS_SWEEP_3_32
and the worldMin/worldMax arguments are omitted,
then the physics space
will extend from (-10000, -10000, -10000) to (+10000, +10000, +10000).
Updating the physics space
PhysicsSpace offers 3 update methods:
space.update(timeInterval, maxSteps, doEnded, doProcessed, doStarted);
space.update(timeInterval, maxSteps);
space.update(timeInterval);To single-step the simulation, specify maxSteps = 0.
The time step will be timeInterval seconds.
Specifying the time step this way allows it to vary from step to step,
without regard for space.getAccuracy() or space.maxTimeStep().
To attempt real-time simulation, specify maxSteps > 0.
The time step will be space.getAccuracy()
and up to maxSteps steps will be simulated for each update.
If the maxSteps argument is omitted, space.maxSubSteps() will be used.
And if space.maxSubSteps() == 0,
then the time step will be capped at space.maxTimeStep() seconds
(as with a BulletAppState).
If you don’t need all 3 kinds of contact callbacks,
you can improve simulation efficiency by specifying false
for doEnded, doProcessed, and/or doStarted.