Rolling resistance

benchmark/amd7950x_avx2/joint_grid.csv

@@ -1,9 +1,9 @@
 threads,ms
-1,2565.3
-2,1533.85
-3,1053.01
-4,865.702
-5,748.989
-6,658.623
-7,613.633
-8,578.973
+1,2528.51
+2,1460.58
+3,1004.38
+4,822.484
+5,712.691
+6,638.201
+7,583.016
+8,540.158

benchmark/amd7950x_avx2/large_pyramid.csv

@@ -1,9 +1,9 @@
 threads,ms
-1,1584.03
-2,841.862
-3,598.747
-4,471.697
-5,396.306
-6,347.983
-7,309.086
-8,308.832
+1,1579.54
+2,849.264
+3,591.984
+4,466.064
+5,393.207
+6,347.593
+7,305.863
+8,305.205

benchmark/amd7950x_avx2/many_pyramids.csv

@@ -1,9 +1,9 @@
 threads,ms
-1,2663.34
-2,1407.85
-3,934.506
-4,725.271
-5,590.288
-6,502.513
-7,422.693
-8,395.369
+1,2592.03
+2,1412.01
+3,953.71
+4,731.394
+5,601.527
+6,511.144
+7,441.201
+8,393.566

benchmark/amd7950x_avx2/rain.csv

@@ -1,9 +1,9 @@
 threads,ms
-1,6526.9
-2,4017.74
-3,3052.28
-4,2493.5
-5,2149.12
-6,1911.45
-7,1735.97
-8,1625.71
+1,6462.19
+2,3806.63
+3,2907
+4,2413.23
+5,2069.53
+6,1852.14
+7,1671.47
+8,1547.16

benchmark/amd7950x_avx2/smash.csv

@@ -1,9 +1,9 @@
 threads,ms
-1,1562.06
-2,1020.55
-3,781.193
-4,661.318
-5,580.115
-6,530.502
-7,489.672
-8,467.998
+1,1533.42
+2,981.749
+3,763.27
+4,642.928
+5,574.053
+6,527.394
+7,492.883
+8,468.971

benchmark/amd7950x_avx2/spinner.csv

@@ -1,9 +1,9 @@
 threads,ms
-1,4106.89
-2,2635.21
-3,1986.32
-4,1614.21
-5,1420.63
-6,1272.06
-7,1157.16
-8,1091.25
+1,4126.1
+2,2491.09
+3,1918.78
+4,1543.11
+5,1360.84
+6,1216.53
+7,1110.95
+8,1043.96

benchmark/amd7950x_avx2/tumbler.csv

@@ -1,9 +1,9 @@
 threads,ms
-1,1613.69
-2,1061.88
-3,810.738
-4,670.874
-5,578.959
-6,519.473
-7,479.842
-8,437.851
+1,1624.23
+2,1028.59
+3,796.538
+4,651.347
+5,563.763
+6,510.42
+7,468.899
+8,445.968

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;
@@ -394,6 +396,35 @@ typedef struct b2ShapeDef
 /// @ingroup shape
 B2_API b2ShapeDef b2DefaultShapeDef( void );
 
+/// Surface materials allow chain shapes to have per segment surface properties.
+/// @ingroup shape
+typedef struct b2SurfaceMaterial
+{
+	/// The Coulomb (dry) friction coefficient, usually in the range [0,1].
+	float friction;
+
+	/// The coefficient of restitution (bounce) usually in the range [0,1].
+	/// https://en.wikipedia.org/wiki/Coefficient_of_restitution
+	float restitution;
+
+	/// The rolling resistance usually in the range [0,1].
+	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;
+
+	/// Custom debug draw color.
+	uint32_t customColor;
+} b2SurfaceMaterial;
+
+/// Use this to initialize your surface material
+/// @ingroup shape
+B2_API b2SurfaceMaterial b2DefaultSurfaceMaterial( void );
+
 /// Used to create a chain of line segments. This is designed to eliminate ghost collisions with some limitations.
 /// - chains are one-sided
 /// - chains have no mass and should be used on static bodies
@@ -420,28 +451,19 @@ typedef struct b2ChainDef
 	/// The point count, must be 4 or more.
 	int count;
 
-	/// The friction coefficient, usually in the range [0,1].
-	float friction;
-
-	/// The restitution (elasticity) usually in the range [0,1].
-	float restitution;
+	/// Surface materials for each segment. These are cloned.
+	const b2SurfaceMaterial* materials;
 
-	/// User material identifier. This is passed with query results and to friction and restitution
-	/// combining functions. It is not used internally.
-	int material;
+	/// The material count. Must be 1 or count. This allows you to provide one
+	/// material for all segments or a unique material per segment.
+	int materialCount;
 
 	/// Contact filtering data.
 	b2Filter filter;
 
-	/// Custom debug draw color.
-	uint32_t customColor;
-
 	/// Indicates a closed chain formed by connecting the first and last points
 	bool isLoop;
 
-	/// Generate events when a sensor overlaps this chain
-	bool enableSensorEvents;
-
 	/// Used internally to detect a valid definition. DO NOT SET.
 	int internalValue;
 } b2ChainDef;

samples/car.cpp

@@ -53,6 +53,7 @@ void Car::Spawn( b2WorldId worldId, b2Vec2 position, float scale, float hertz, f
 
 	shapeDef.density = 2.0f / scale;
 	shapeDef.friction = 1.5f;
+	shapeDef.rollingResistance = 0.1f;
 
 	bodyDef.position = b2Add( { -1.0f * scale, 0.35f * scale }, position );
 	bodyDef.allowFastRotation = true;

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;