Wind (#980)

- added b2Shape_ApplyWind and sample
- added b2Body_WakeTouching and sample
- b2DestroyJoint now takes a flag to wake the connected bodies
- fixed bug in b2HashSet and b2SetItem no longer holds a copy of the
hash
- added more samples and unit tests

#978

Author: erincatto

benchmark/amd7950x_sse2/washer.csv

@@ -1,9 +1,9 @@
 threads,ms
-1,8001.88
-2,4492.59
-3,3213.91
-4,2543.84
-5,2112.88
-6,1832.15
-7,1641.22
-8,1498.33
+1,7934.7
+2,4531.48
+3,3218.58
+4,2523.46
+5,2100.84
+6,1842.67
+7,1638.05
+8,1529.17

benchmark/main.c

@@ -140,7 +140,7 @@ static void MinProfile( b2Profile* p1, const b2Profile* p2 )
 
 // Run benchmark 3 with 4 workers and repeat 20 times. Record the step times.
 // start /affinity 0x5555 .\build\bin\Release\benchmark.exe -t=4 -w=4 -b=3 -r=20 -s
-// start /affinity 0x5555 .\build\bin\Release\benchmark.exe -t=8 -b=5
+// start /affinity 0x5555 .\build\bin\Release\benchmark.exe -t=8 -b=7
 
 // Run benchmark 3 with 4 workers and run once. Disable continuous collision. Record the step times.
 // start /affinity 0x5555 .\build\bin\Release\benchmark.exe -t=4 -w=4 -b=3 -r=1 -nc -s

include/box2d/box2d.h

@@ -397,6 +397,9 @@ B2_API bool b2Body_IsAwake( b2BodyId bodyId );
 /// which can be expensive and possibly unintuitive.
 B2_API void b2Body_SetAwake( b2BodyId bodyId, bool awake );
 
+/// Wake bodies touching this body. Works for static bodies.
+B2_API void b2Body_WakeTouching( b2BodyId bodyId );
+
 /// Enable or disable sleeping for this body. If sleeping is disabled the body will wake.
 B2_API void b2Body_EnableSleep( b2BodyId bodyId, bool enableSleep );
 
@@ -677,6 +680,8 @@ B2_API b2MassData b2Shape_ComputeMassData( b2ShapeId shapeId );
 /// todo need sample
 B2_API b2Vec2 b2Shape_GetClosestPoint( b2ShapeId shapeId, b2Vec2 target );
 
+B2_API void b2Shape_ApplyWindForce( b2ShapeId shapeId, b2Vec2 wind, float drag, float lift, bool wake );
+
 /// Chain Shape
 
 /// Create a chain shape
@@ -717,8 +722,8 @@ B2_API bool b2Chain_IsValid( b2ChainId id );
  * @{
  */
 
-/// Destroy a joint
-B2_API void b2DestroyJoint( b2JointId jointId );
+/// Destroy a joint. Optionally wake attached bodies.
+B2_API void b2DestroyJoint( b2JointId jointId, bool wakeAttached );
 
 /// Joint identifier validation. Provides validation for up to 64K allocations.
 B2_API bool b2Joint_IsValid( b2JointId id );

samples/car.cpp

@@ -112,8 +112,8 @@ void Car::Despawn()
 {
 	assert( m_isSpawned == true );
 
-	b2DestroyJoint( m_rearAxleId );
-	b2DestroyJoint( m_frontAxleId );
+	b2DestroyJoint( m_rearAxleId, false );
+	b2DestroyJoint( m_frontAxleId, false );
 	b2DestroyBody( m_rearWheelId );
 	b2DestroyBody( m_frontWheelId );
 	b2DestroyBody( m_chassisId );
@@ -261,8 +261,8 @@ void Truck::Despawn()
 {
 	assert( m_isSpawned == true );
 
-	b2DestroyJoint( m_rearAxleId );
-	b2DestroyJoint( m_frontAxleId );
+	b2DestroyJoint( m_rearAxleId, false );
+	b2DestroyJoint( m_frontAxleId, false );
 	b2DestroyBody( m_rearWheelId );
 	b2DestroyBody( m_frontWheelId );
 	b2DestroyBody( m_chassisId );

samples/doohickey.cpp

@@ -89,9 +89,9 @@ void Doohickey::Despawn()
 {
 	assert( m_isSpawned == true );
 
-	b2DestroyJoint( m_axleId1 );
-	b2DestroyJoint( m_axleId2 );
-	b2DestroyJoint( m_sliderId );
+	b2DestroyJoint( m_axleId1, false );
+	b2DestroyJoint( m_axleId2, false );
+	b2DestroyJoint( m_sliderId, false );
 
 	b2DestroyBody( m_wheelId1 );
 	b2DestroyBody( m_wheelId2 );

samples/sample.cpp

@@ -355,7 +355,7 @@ void Sample::MouseDown( b2Vec2 p, int button, int mod )
 			{
 				// This acts like angular friction
 				float lever = sqrtf( massData.rotationalInertia / massData.mass );
-				jointDef.maxVelocityTorque = 1.0f * lever * mg;
+				jointDef.maxVelocityTorque = 0.25f * lever * mg;
 			}
 
 			m_mouseJointId = b2CreateMotorJoint( m_worldId, &jointDef );
@@ -367,7 +367,7 @@ void Sample::MouseUp( b2Vec2 p, int button )
 {
 	if ( B2_IS_NON_NULL( m_mouseJointId ) && button == GLFW_MOUSE_BUTTON_1 )
 	{
-		b2DestroyJoint( m_mouseJointId );
+		b2DestroyJoint( m_mouseJointId, true );
 		m_mouseJointId = b2_nullJointId;
 
 		b2DestroyBody( m_mouseBodyId );

samples/sample_benchmark.cpp

@@ -935,7 +935,7 @@ class BenchmarkSleep : public Sample
 			uint64_t ticks = b2GetTicks();
 
 			// This will wake the island
-			b2DestroyJoint( jointId );
+			b2DestroyJoint( jointId, true );
 			m_wakeTotal += b2GetMillisecondsAndReset( &ticks );
 
 			// Put the island back to sleep. It must be split because a constraint was removed.

samples/sample_bodies.cpp

@@ -1040,3 +1040,72 @@ class SetVelocity : public Sample
 };
 
 static int sampleSetVelocity = RegisterSample( "Bodies", "Set Velocity", SetVelocity::Create );
+
+class WakeTouching : public Sample
+{
+public:
+	explicit WakeTouching( SampleContext* context )
+		: Sample( context )
+	{
+		if ( m_context->restart == false )
+		{
+			m_context->camera.m_center = { 0.0f, 4.0f };
+			m_context->camera.m_zoom = 8.0f;
+		}
+
+		{
+			b2BodyDef bodyDef = b2DefaultBodyDef();
+			m_groundId = b2CreateBody( m_worldId, &bodyDef );
+
+			b2Segment segment = { { -20.0f, 0.0f }, { 20.0f, 0.0f } };
+			b2ShapeDef shapeDef = b2DefaultShapeDef();
+			b2CreateSegmentShape( m_groundId, &shapeDef, &segment );
+		}
+
+		b2Polygon box = b2MakeBox( 0.5f, 0.5f );
+
+		b2ShapeDef shapeDef = b2DefaultShapeDef();
+		shapeDef.density = 1.0f;
+
+		b2BodyDef bodyDef = b2DefaultBodyDef();
+		bodyDef.type = b2_dynamicBody;
+
+		float x = -1.0f * ( m_count - 1 );
+
+		for ( int i = 0; i < m_count; ++i )
+		{
+			bodyDef.position = { x, 4.0f };
+			b2BodyId bodyId = b2CreateBody( m_worldId, &bodyDef );
+			b2CreatePolygonShape( bodyId, &shapeDef, &box );
+			x += 2.0f;
+		}
+	}
+
+	void UpdateGui() override
+	{
+		float fontSize = ImGui::GetFontSize();
+		float height = 5.0f * fontSize;
+		ImGui::SetNextWindowPos( ImVec2( 0.5f * fontSize, m_camera->m_height - height - 2.0f * fontSize ), ImGuiCond_Once );
+		ImGui::SetNextWindowSize( ImVec2( 10.0f * fontSize, height ) );
+
+		ImGui::Begin( "Wake Touching", nullptr, ImGuiWindowFlags_NoResize );
+
+		if ( ImGui::Button( "Wake Touching" ) )
+		{
+			b2Body_WakeTouching( m_groundId );
+		}
+
+		ImGui::End();
+	}
+
+	static Sample* Create( SampleContext* context )
+	{
+		return new WakeTouching( context );
+	}
+
+	static constexpr int m_count = 10;
+
+	b2BodyId m_groundId;
+};
+
+static int sampleWakeTouching = RegisterSample( "Bodies", "Wake Touching", WakeTouching::Create );

samples/sample_determinism.cpp

@@ -46,7 +46,7 @@ class FallingHinges : public Sample
 		}
 		else
 		{
-			DrawTextLine( "sleep step = %d, hash = 0x%08x", m_data.sleepStep, m_data.hash );
+			DrawTextLine( "sleep step = %d, hash = 0x%08X", m_data.sleepStep, m_data.hash );
 		}
 	}
 

samples/sample_events.cpp

@@ -2056,7 +2056,7 @@ class JointEvent : public Sample
 			{
 				int index = (int)(intptr_t)event->userData;
 				assert( 0 <= index && index < e_count );
-				b2DestroyJoint( event->jointId );
+				b2DestroyJoint( event->jointId, true );
 				m_jointIds[index] = b2_nullJointId;
 			}
 		}