wip

include/box2d/collision.h

@@ -535,14 +535,18 @@ typedef struct b2ManifoldPoint
 /// @note Box2D uses speculative collision so some contact points may be separated.
 typedef struct b2Manifold
 {
-	/// The manifold points, up to two are possible in 2D
-	b2ManifoldPoint points[2];
-
 	/// The unit normal vector in world space, points from shape A to bodyB
 	b2Vec2 normal;
 
+	/// Angular impulse applied for rolling resistance. N * m * s = kg * m^2 / s
+	float rollingImpulse;
+
+	/// The manifold points, up to two are possible in 2D
+	b2ManifoldPoint points[2];
+
 	/// The number of contacts points, will be 0, 1, or 2
 	int pointCount;
+
 } b2Manifold;
 
 /// Compute the contact manifold between two circles

include/box2d/types.h

@@ -346,9 +346,11 @@ typedef struct b2ShapeDef
 	float restitution;
 
 	/// The rolling resistance usually in the range [0,1].
-	/// todo
 	float rollingResistance;
 
+	/// The tangent speed for conveyor belts
+	float tangentSpeed;
+
 	/// User material identifier. This is passed with query results and to friction and restitution
 	/// combining functions. It is not used internally.
 	int material;

samples/main.cpp

@@ -640,8 +640,6 @@ int main( int, char** )
 
 	float frameTime = 0.0;
 
-	// int32_t frame = 0;
-
 	while ( !glfwWindowShouldClose( g_mainWindow ) )
 	{
 		double time1 = glfwGetTime();
@@ -754,21 +752,14 @@ int main( int, char** )
 
 		// Limit frame rate to 60Hz
 		double time2 = glfwGetTime();
-		double targetTime = time1 + 1.0f / 60.0f;
-		// int loopCount = 0;
+		double targetTime = time1 + 1.0 / 60.0;
 		while ( time2 < targetTime )
 		{
 			b2Yield();
 			time2 = glfwGetTime();
-			//++loopCount;
 		}
 
-		frameTime = (float)( time2 - time1 );
-		// if (frame % 17 == 0)
-		//{
-		//	printf("loop count = %d, frame time = %.1f\n", loopCount, 1000.0f * frameTime);
-		// }
-		//++frame;
+		frameTime = float( time2 - time1 );
 	}
 
 	delete s_sample;

samples/sample.cpp

@@ -101,14 +101,8 @@ Sample::Sample( Settings& settings )
 
 	m_threadCount = 1 + settings.workerCount;
 
-	b2WorldDef worldDef = b2DefaultWorldDef();
-	worldDef.workerCount = settings.workerCount;
-	worldDef.enqueueTask = EnqueueTask;
-	worldDef.finishTask = FinishTask;
-	worldDef.userTaskContext = this;
-	worldDef.enableSleep = settings.enableSleep;
+	m_worldId = b2_nullWorldId;
 
-	m_worldId = b2CreateWorld( &worldDef );
 	m_textLine = 30;
 	m_textIncrement = 22;
 	m_mouseJointId = b2_nullJointId;
@@ -122,6 +116,9 @@ Sample::Sample( Settings& settings )
 
 	g_seed = RAND_SEED;
 
+	m_settings = &settings;
+
+	CreateWorld( );
 	TestMathCpp();
 }
 
@@ -134,6 +131,24 @@ Sample::~Sample()
 	delete[] m_tasks;
 }
 
+void Sample::CreateWorld(  )
+{
+	if ( B2_IS_NON_NULL( m_worldId ) )
+	{
+		b2DestroyWorld( m_worldId );
+		m_worldId = b2_nullWorldId;
+	}
+
+	b2WorldDef worldDef = b2DefaultWorldDef();
+	worldDef.workerCount = m_settings->workerCount;
+	worldDef.enqueueTask = EnqueueTask;
+	worldDef.finishTask = FinishTask;
+	worldDef.userTaskContext = this;
+	worldDef.enableSleep = m_settings->enableSleep;
+
+	m_worldId = b2CreateWorld( &worldDef );
+}
+
 void Sample::DrawTitle( const char* string )
 {
 	g_draw.DrawString( 5, 5, string );

samples/sample.h

@@ -5,11 +5,10 @@
 
 #include "box2d/id.h"
 #include "box2d/types.h"
+#include "settings.h"
 
 #define ARRAY_COUNT( A ) (int)( sizeof( A ) / sizeof( A[0] ) )
 
-struct Settings;
-
 namespace enki
 {
 class TaskScheduler;
@@ -43,6 +42,8 @@ class Sample
 	explicit Sample( Settings& settings );
 	virtual ~Sample();
 
+	void CreateWorld( );
+
 	void DrawTitle( const char* string );
 	virtual void Step( Settings& settings );
 	virtual void UpdateUI()
@@ -66,9 +67,9 @@ class Sample
 	static constexpr int m_maxTasks = 64;
 	static constexpr int m_maxThreads = 64;
 
+	const Settings* m_settings;
 	enki::TaskScheduler* m_scheduler;
 	class SampleTask* m_tasks;
-
 	int m_taskCount;
 	int m_threadCount;
 

samples/sample_benchmark.cpp

@@ -557,7 +557,7 @@ class BenchmarkLargePyramid : public Sample
 			settings.enableSleep = false;
 		}
 
-		CreateLargePyramid(m_worldId);
+		CreateLargePyramid( m_worldId );
 	}
 
 	static Sample* Create( Settings& settings )
@@ -624,13 +624,18 @@ class BenchmarkCreateDestroy : public Sample
 			m_bodies[i] = b2_nullBodyId;
 		}
 
+		m_createTime = 0.0f;
+		m_destroyTime = 0.0f;
+
 		m_baseCount = g_sampleDebug ? 40 : 100;
 		m_iterations = g_sampleDebug ? 1 : 10;
 		m_bodyCount = 0;
 	}
 
 	void CreateScene()
 	{
+		uint64_t ticks = b2GetTicks();
+
 		for ( int i = 0; i < e_maxBodyCount; ++i )
 		{
 			if ( B2_IS_NON_NULL( m_bodies[i] ) )
@@ -640,6 +645,8 @@ class BenchmarkCreateDestroy : public Sample
 			}
 		}
 
+		m_destroyTime += b2GetMillisecondsAndReset( &ticks );
+
 		int count = m_baseCount;
 		float rad = 0.5f;
 		float shift = rad * 2.0f;
@@ -675,22 +682,28 @@ class BenchmarkCreateDestroy : public Sample
 			}
 		}
 
+		m_createTime += b2GetMilliseconds( ticks );
+
 		m_bodyCount = index;
+
+		b2World_Step( m_worldId, 1.0f / 60.0f, 4 );
 	}
 
 	void Step( Settings& settings ) override
 	{
-		uint64_t ticks = b2GetTicks();
+		m_createTime = 0.0f;
+		m_destroyTime = 0.0f;
 
 		for ( int i = 0; i < m_iterations; ++i )
 		{
 			CreateScene();
 		}
 
-		float ms = b2GetMilliseconds( ticks );
+		DrawTextLine( "total: create = %g ms, destroy = %g ms", m_createTime, m_destroyTime );
 
-		g_draw.DrawString( 5, m_textLine, "milliseconds = %g", ms );
-		m_textLine += m_textIncrement;
+		float createPerBody = 1000.0f * m_createTime / m_iterations / m_bodyCount;
+		float destroyPerBody = 1000.0f * m_destroyTime / m_iterations / m_bodyCount;
+		DrawTextLine( "body: create = %g us, destroy = %g us", createPerBody, destroyPerBody );
 
 		Sample::Step( settings );
 	}
@@ -700,6 +713,8 @@ class BenchmarkCreateDestroy : public Sample
 		return new BenchmarkCreateDestroy( settings );
 	}
 
+	float m_createTime;
+	float m_destroyTime;
 	b2BodyId m_bodies[e_maxBodyCount];
 	int m_bodyCount;
 	int m_baseCount;
@@ -1529,14 +1544,14 @@ class BenchmarkRain : public Sample
 
 	void Step( Settings& settings ) override
 	{
-		if (settings.pause == false || settings.singleStep == true)
+		if ( settings.pause == false || settings.singleStep == true )
 		{
 			StepRain( m_worldId, m_stepCount );
 		}
 
 		Sample::Step( settings );
 
-		if (m_stepCount % 1000 == 0)
+		if ( m_stepCount % 1000 == 0 )
 		{
 			m_stepCount += 0;
 		}

samples/sample_shapes.cpp

@@ -952,7 +952,96 @@ class Friction : public Sample
 	}
 };
 
-static int sampleIndex3 = RegisterSample( "Shapes", "Friction", Friction::Create );
+static int sampleFriction = RegisterSample( "Shapes", "Friction", Friction::Create );
+
+class RollingResistance : public Sample
+{
+public:
+	explicit RollingResistance( Settings& settings )
+		: Sample( settings )
+	{
+		if ( settings.restart == false )
+		{
+			g_camera.m_center = { 5.0f, 20.0f };
+			g_camera.m_zoom = 27.5f;
+		}
+
+		m_lift = 0.0f;
+		CreateScene();
+	}
+
+	void CreateScene()
+	{
+		b2Circle circle = { b2Vec2_zero, 0.5f };
+
+		b2ShapeDef shapeDef = b2DefaultShapeDef();
+
+		for ( int i = 0; i < 20; ++i )
+		{
+			b2BodyDef bodyDef = b2DefaultBodyDef();
+			b2BodyId groundId = b2CreateBody( m_worldId, &bodyDef );
+
+			b2Segment segment = { { -40.0f, 2.0f * i }, { 40.0f, 2.0f * i + m_lift } };
+			b2CreateSegmentShape( groundId, &shapeDef, &segment );
+
+			bodyDef.type = b2_dynamicBody;
+			bodyDef.position = { -39.5f, 2.0f * i + 0.75f };
+			bodyDef.angularVelocity = -10.0f;
+			bodyDef.linearVelocity = { 5.0f, 0.0f };
+
+			b2BodyId bodyId = b2CreateBody( m_worldId, &bodyDef );
+			shapeDef.rollingResistance = 0.1f * i;
+			b2CreateCircleShape( bodyId, &shapeDef, &circle );
+		}
+	}
+
+	void Keyboard( int key ) override
+	{
+		switch ( key )
+		{
+			case GLFW_KEY_1:
+				m_lift = 0.0f;
+				CreateWorld();
+				CreateScene();
+				break;
+
+			case GLFW_KEY_2:
+				m_lift = 5.0f;
+				CreateWorld();
+				CreateScene();
+				break;
+
+			case GLFW_KEY_3:
+				m_lift = -5.0f;
+				CreateWorld();
+				CreateScene();
+				break;
+
+			default:
+				Sample::Keyboard( key );
+				break;
+		}
+	}
+
+	void Step( Settings& settings ) override
+	{
+		Sample::Step( settings );
+
+		for ( int i = 0; i < 20; ++i )
+		{
+			g_draw.DrawString( { -41.5f, 2.0f * i + 1.0f }, "%.2f", 0.1f * i );
+		}
+	}
+
+	static Sample* Create( Settings& settings )
+	{
+		return new RollingResistance( settings );
+	}
+
+	float m_lift;
+};
+
+static int sampleRollingResistance = RegisterSample( "Shapes", "Rolling Resistance", RollingResistance::Create );
 
 // This sample shows how to modify the geometry on an existing shape. This is only supported on
 // dynamic and kinematic shapes because static shapes don't look for new collisions.