maximum linear velocity in world def

allow fast rotation in body def
fix for wasm

include/box2d/types.h

@@ -88,6 +88,9 @@ typedef struct b2WorldDef
 	/// Joint bounciness. Non-dimensional.
 	float jointDampingRatio;
 
+	/// Maximum linear velocity. Usually meters per second.
+	float maximumLinearVelocity;
+
 	/// Can bodies go to sleep to improve performance
 	bool enableSleep;
 
@@ -202,6 +205,10 @@ typedef struct b2BodyDef
 	/// Triggers whenever a shape is add/removed/changed. Default is true.
 	bool automaticMass;
 
+	/// This allows this body to bypass rotational speed limits. Should only be used
+	///	for circular objects, like wheels.
+	bool allowFastRotation;
+
 	/// Used internally to detect a valid definition. DO NOT SET.
 	int32_t internalValue;
 } b2BodyDef;

samples/car.cpp

@@ -55,10 +55,12 @@ void Car::Spawn( b2WorldId worldId, b2Vec2 position, float scale, float hertz, f
 	shapeDef.friction = 1.5f;
 
 	bodyDef.position = b2Add( { -1.0f * scale, 0.35f * scale }, position );
+	bodyDef.allowFastRotation = true;
 	m_rearWheelId = b2CreateBody( worldId, &bodyDef );
 	b2CreateCircleShape( m_rearWheelId, &shapeDef, &circle );
 
 	bodyDef.position = b2Add( { 1.0f * scale, 0.4f * scale }, position );
+	bodyDef.allowFastRotation = true;
 	m_frontWheelId = b2CreateBody( worldId, &bodyDef );
 	b2CreateCircleShape( m_frontWheelId, &shapeDef, &circle );
 

samples/sample_continuous.cpp

@@ -82,6 +82,10 @@ class BounceHouse : public Sample
 		bodyDef.linearVelocity = { 10.0f, 20.0f };
 		bodyDef.position = { 0.0f, 0.0f };
 		bodyDef.gravityScale = 0.0f;
+
+		// Circle shapes centered on the body can spin fast without risk of tunnelling.
+		bodyDef.allowFastRotation = m_shapeType == e_circleShape;
+
 		m_bodyId = b2CreateBody( m_worldId, &bodyDef );
 
 		b2ShapeDef shapeDef = b2DefaultShapeDef();

src/body.c

@@ -254,6 +254,7 @@ b2BodyId b2CreateBody( b2WorldId worldId, const b2BodyDef* def )
 	bodySim->gravityScale = def->gravityScale;
 	bodySim->bodyId = bodyId;
 	bodySim->isBullet = def->isBullet;
+	bodySim->allowFastRotation = def->allowFastRotation;
 	bodySim->enlargeAABB = false;
 	bodySim->isFast = false;
 	bodySim->isSpeedCapped = false;

src/body.h

@@ -129,6 +129,7 @@ typedef struct b2BodySim
 	bool isFast;
 	bool isBullet;
 	bool isSpeedCapped;
+	bool allowFastRotation;
 	bool enlargeAABB;
 } b2BodySim;
 

src/core.h

@@ -61,18 +61,18 @@
 
 #if defined( B2_COMPILER_MSVC )
 	#define B2_BREAKPOINT __debugbreak()
-#elif defined( B2_COMPILER_GCC ) || defined( B2_COMPILER_CLANG )
-	#if defined( B2_CPU_X64 )
-		#define B2_BREAKPOINT __asm volatile( "int $0x3" )
-	#elif defined( B2_CPU_ARM )
-		#define B2_BREAKPOINT __builtin_trap()
-	#endif
 #elif defined( B2_PLATFORM_WASM )
 	#define B2_BREAKPOINT                                                                                                        \
 		do                                                                                                                       \
 		{                                                                                                                        \
 		}                                                                                                                        \
 		while ( 0 )
+#elif defined( B2_COMPILER_GCC ) || defined( B2_COMPILER_CLANG )
+	#if defined( B2_CPU_X64 )
+		#define B2_BREAKPOINT __asm volatile( "int $0x3" )
+	#elif defined( B2_CPU_ARM )
+		#define B2_BREAKPOINT __builtin_trap()
+	#endif
 #else
 	#error Unknown platform
 #endif
@@ -128,14 +128,9 @@ extern float b2_lengthUnitsPerMeter;
 // Maximum number of simultaneous worlds that can be allocated
 #define b2_maxWorlds 128
 
-// The maximum translation of a body per time step. This limit is very large and is used
-// to prevent numerical problems. You shouldn't need to adjust this. Meters.
-// @warning modifying this can have a significant impact on stability
-#define b2_maxTranslation ( 4.0f * b2_lengthUnitsPerMeter )
-
 // The maximum rotation of a body per time step. This limit is very large and is used
 // to prevent numerical problems. You shouldn't need to adjust this.
-// @warning modifying this can have a significant impact on stability
+// @warning increasing this to 0.5f * b2_pi or greater will break continuous collision.
 #define b2_maxRotation ( 0.25f * b2_pi )
 
 // @warning modifying this can have a significant impact on performance and stability

src/solver.c

@@ -40,7 +40,7 @@ static void b2IntegrateVelocitiesTask( int startIndex, int endIndex, b2StepConte
 
 	b2Vec2 gravity = context->world->gravity;
 	float h = context->h;
-	float maxLinearSpeed = b2_maxTranslation * context->inv_dt;
+	float maxLinearSpeed = context->maxLinearVelocity;
 	float maxAngularSpeed = b2_maxRotation * context->inv_dt;
 	float maxLinearSpeedSquared = maxLinearSpeed * maxLinearSpeed;
 	float maxAngularSpeedSquared = maxAngularSpeed * maxAngularSpeed;
@@ -78,7 +78,7 @@ static void b2IntegrateVelocitiesTask( int startIndex, int endIndex, b2StepConte
 		}
 
 		// Clamp to max angular speed
-		if ( w * w > maxAngularSpeedSquared )
+		if ( w * w > maxAngularSpeedSquared && sim->allowFastRotation == false )
 		{
 			float ratio = maxAngularSpeed / b2AbsFloat( w );
 			w *= ratio;

src/solver.h

@@ -91,6 +91,7 @@ typedef struct b2StepContext
 	b2Softness staticSoftness;
 
 	float restitutionThreshold;
+	float maxLinearVelocity;
 
 	struct b2World* world;
 	struct b2ConstraintGraph* graph;

src/types.c

@@ -17,6 +17,8 @@ b2WorldDef b2DefaultWorldDef( void )
 	def.contactDampingRatio = 10.0f;
 	def.jointHertz = 60.0;
 	def.jointDampingRatio = 2.0f;
+	// 400 meters per second, faster than the speed of sound
+	def.maximumLinearVelocity = 400.0f * b2_lengthUnitsPerMeter;
 	def.enableSleep = true;
 	def.enableContinous = true;
 	def.internalValue = B2_SECRET_COOKIE;

src/world.c

@@ -165,6 +165,7 @@ b2WorldId b2CreateWorld( const b2WorldDef* def )
 	world->gravity = def->gravity;
 	world->hitEventThreshold = def->hitEventThreshold;
 	world->restitutionThreshold = def->restitutionThreshold;
+	world->maxLinearVelocity = def->maximumLinearVelocity;
 	world->contactPushoutVelocity = def->contactPushoutVelocity;
 	world->contactHertz = def->contactHertz;
 	world->contactDampingRatio = def->contactDampingRatio;
@@ -743,6 +744,7 @@ void b2World_Step( b2WorldId worldId, float timeStep, int subStepCount )
 	context.jointSoftness = b2MakeSoft( jointHertz, world->jointDampingRatio, context.h );
 
 	context.restitutionThreshold = world->restitutionThreshold;
+	context.maxLinearVelocity = world->maxLinearVelocity;
 	context.enableWarmStarting = world->enableWarmStarting;
 
 	// Update contacts

src/world.h

@@ -125,6 +125,7 @@ typedef struct b2World
 	b2Vec2 gravity;
 	float hitEventThreshold;
 	float restitutionThreshold;
+	float maxLinearVelocity;
 	float contactPushoutVelocity;
 	float contactHertz;
 	float contactDampingRatio;