Persistent islands (#36)

Persistent islands - islands are merged and split incrementally rather
than being rebuilt every time step.
Sleeping is now per island rather than per body.

Merging uses union-find. Each body created also creates an island. When
joints are created the islands are linked and merged. When contacts
begin touching the islands are linked and merged.

When a contact stops touching or is destroyed the island is flagged for
splitting. Likewise destroying a joint flags the island for splitting.
Only a single island may be split per time step. The largest island is
chosen. Island splitting is handled in the island job.

The parallel collide tasks generate state changes for contacts. These
are processed in deterministic order to maintain overall determinism.

CMakeLists.txt

@@ -17,6 +17,9 @@ if (MSVC AND WIN32)
     # Enable edit and continue only in debug due to perf hit in release
     add_link_options($<$<CONFIG:Debug>:/INCREMENTAL>)
     add_compile_options($<$<CONFIG:Debug>:/ZI>)
+
+	# this seems useless because it crashes in KernalBase.dll
+	# add_compile_options(/fsanitize=address)
 endif()
 
 if (BOX2D_PROFILE)

include/box2d/box2d.h

@@ -6,6 +6,7 @@
 #include "box2d/api.h"
 #include "box2d/id.h"
 #include "box2d/joint_types.h"
+#include "box2d/timer.h"
 #include "box2d/types.h"
 
 typedef struct b2Circle b2Circle;
@@ -33,12 +34,10 @@ BOX2D_API void b2World_Draw(b2WorldId worldId, b2DebugDraw* debugDraw);
 BOX2D_API void b2World_EnableSleeping(b2WorldId worldId, bool flag);
 
 /// Get the current profile.
-BOX2D_API struct b2Profile* b2World_GetProfile(b2WorldId worldId);
+BOX2D_API struct b2Profile b2World_GetProfile(b2WorldId worldId);
 
 BOX2D_API struct b2Statistics b2World_GetStatistics(b2WorldId worldId);
 
-BOX2D_API b2BodyId b2World_GetGroundBodyId(b2WorldId worldId);
-
 /// Create a rigid body given a definition. No reference to the definition is retained.
 /// @warning This function is locked during callbacks.
 BOX2D_API b2BodyId b2World_CreateBody(b2WorldId worldId, const b2BodyDef* def);
@@ -53,7 +52,7 @@ BOX2D_API b2Vec2 b2Body_GetLocalPoint(b2BodyId bodyId, b2Vec2 globalPoint);
 
 BOX2D_API b2BodyType b2Body_GetType(b2BodyId bodyId);
 BOX2D_API float b2Body_GetMass(b2BodyId bodyId);
-BOX2D_API void b2Body_SetAwake(b2BodyId bodyId, bool awake);
+BOX2D_API void b2Body_Wake(b2BodyId bodyId);
 
 /// Create a shape and attach it to a body. Contacts are not created until the next time step.
 /// @warning This function is locked during callbacks.

include/box2d/joint_types.h

@@ -5,7 +5,6 @@
 
 #include "box2d/types.h"
 
-
 /// A mouse joint is used to make a point on a body track a
 /// specified world point. This a soft constraint with a maximum
 /// force. This allows the constraint to stretch without
@@ -15,11 +14,13 @@
 /// use the mouse joint, look at the samples app.
 typedef struct b2MouseJointDef
 {
-	/// The attached body. It should be dynamic.
-	b2BodyId bodyId;
+	/// The first attached body.
+	b2BodyId bodyIdA;
+
+	/// The second attached body.
+	b2BodyId bodyIdB;
 
-	/// The initial world target point. This is assumed
-	/// to coincide with the body anchor initially.
+	/// The initial target point in world space
 	b2Vec2 target;
 
 	/// The maximum constraint force that can be exerted
@@ -37,7 +38,8 @@ typedef struct b2MouseJointDef
 static inline struct b2MouseJointDef b2DefaultMouseJointDef()
 {
 	b2MouseJointDef def = {0};
-	def.bodyId = b2_nullBodyId;
+	def.bodyIdA = b2_nullBodyId;
+	def.bodyIdB = b2_nullBodyId;
 	def.target = B2_LITERAL(b2Vec2){0.0f, 0.0f};
 	def.maxForce = 0.0f;
 	def.stiffness = 0.0f;

include/box2d/timer.h

@@ -6,6 +6,7 @@
 #include "types.h"
 
 /// Profiling data. Times are in milliseconds.
+/// TODO_ERIN change to ticks due to variable frequency
 typedef struct b2Profile
 {
 	float step;
@@ -20,6 +21,7 @@ static const b2Profile b2_emptyProfile = {0};
 
 typedef struct b2Statistics
 {
+	int32_t islandCount;
 	int32_t bodyCount;
 	int32_t contactCount;
 	int32_t jointCount;

include/box2d/types.h

@@ -21,6 +21,13 @@
 #define B2_MAYBE_UNUSED(x) ((void)(x))
 #define B2_NULL_INDEX (-1)
 
+// TODO_ERIN temp until github updates MSVC
+//#if defined(_MSC_VER) && !defined(__clang__)
+//#define B2_ATOMIC
+//#else
+#define B2_ATOMIC _Atomic
+//#endif
+
 /// 2D vector
 typedef struct b2Vec2
 {
@@ -75,7 +82,7 @@ typedef struct b2RayCastOutput
 
 /// Task interface
 /// This is prototype for a Box2D task
-typedef void b2TaskCallback(int32_t startIndex, int32_t endIndex, void* context);
+typedef void b2TaskCallback(int32_t startIndex, int32_t endIndex, uint32_t threadIndex, void* context);
 
 /// These functions can be provided to Box2D to invoke a task system
 typedef void b2EnqueueTaskCallback(b2TaskCallback* task, int32_t itemCount, int32_t minRange, void* taskContext, void* userContext);
@@ -93,22 +100,25 @@ typedef struct b2WorldDef
 	/// Can bodies go to sleep to improve performance
 	bool enableSleep;
 
-	/// initial capacity for bodies
+	/// Capacity for bodies. This may not be exceeded.
 	int32_t bodyCapacity;
 
-	/// initial capacity for joints
-	int32_t jointCapacity;
-
 	/// initial capacity for shapes
 	int32_t shapeCapacity;
 
+	/// Capacity for contacts. This may not be exceeded.
+	int32_t contactCapacity;
+
+	/// Capacity for joints
+	int32_t jointCapacity;
+
 	/// Stack allocator capacity. This controls how much space box2d reserves for per-frame calculations.
 	/// Larger worlds require more space. b2Statistics can be used to determine a good capacity for your
 	/// application.
 	int32_t stackAllocatorCapacity;
 
 	/// task system hookup
-	int32_t workerCount;
+	uint32_t workerCount;
 	b2EnqueueTaskCallback* enqueueTask;
 	b2FinishTasksCallback* finishTasks;
 	void* userTaskContext;
@@ -228,8 +238,9 @@ static inline b2WorldDef b2DefaultWorldDef()
 	def.restitutionThreshold = 1.0f * b2_lengthUnitsPerMeter;
 	def.enableSleep = true;
 	def.bodyCapacity = 8;
-	def.jointCapacity = 8;
 	def.shapeCapacity = 8;
+	def.contactCapacity = 8;
+	def.jointCapacity = 8;
 	def.stackAllocatorCapacity = 1024 * 1024;
 	return def;
 }

samples/collection/benchmark_barrel.cpp

@@ -8,8 +8,6 @@
 #include <GLFW/glfw3.h>
 #include <imgui.h>
 
-BOX2D_API bool g_velocityBlockSolve;
-
 class BenchmarkBarrel : public Sample
 {
 public:
@@ -25,7 +23,8 @@ class BenchmarkBarrel : public Sample
 		e_maxRows = 130,
 	};
 
-	BenchmarkBarrel()
+	BenchmarkBarrel(const Settings& settings)
+		: Sample(settings)
 	{
 		float groundSize = 25.0f;
 
@@ -132,8 +131,6 @@ class BenchmarkBarrel : public Sample
 		changed = changed || ImGui::Combo("Shape", &shapeType, shapeTypes, IM_ARRAYSIZE(shapeTypes));
 		m_shapeType = ShapeType(shapeType);
 
-		ImGui::Checkbox("Block Solve", &g_velocityBlockSolve);
-
 		changed = changed || ImGui::Button("Reset Scene");
 
 		if (changed)
@@ -144,9 +141,9 @@ class BenchmarkBarrel : public Sample
 		ImGui::End();
 	}
 
-	static Sample* Create()
+	static Sample* Create(const Settings& settings)
 	{
-		return new BenchmarkBarrel;
+		return new BenchmarkBarrel(settings);
 	}
 
 	b2BodyId m_bodies[e_maxRows * e_maxColumns];

samples/collection/benchmark_joint_grid.cpp

@@ -11,7 +11,8 @@
 class BenchmarkJointGrid : public Sample
 {
 public:
-	BenchmarkJointGrid()
+	BenchmarkJointGrid(const Settings& settings)
+		: Sample(settings)
 	{
 		constexpr float rad = 0.4f;
 		constexpr int32_t numi = g_sampleDebug ? 10 : 100;
@@ -79,9 +80,9 @@ class BenchmarkJointGrid : public Sample
 		b2Free(bodies);
 	}
 
-	static Sample* Create()
+	static Sample* Create(const Settings& settings)
 	{
-		return new BenchmarkJointGrid;
+		return new BenchmarkJointGrid(settings);
 	}
 };
 

samples/collection/benchmark_pyramid.cpp

@@ -8,9 +8,6 @@
 #include <GLFW/glfw3.h>
 #include <imgui.h>
 
-BOX2D_API bool g_velocityBlockSolve;
-BOX2D_API bool g_positionBlockSolve;
-
 class BenchmarkPyramid : public Sample
 {
 public:
@@ -21,7 +18,8 @@ class BenchmarkPyramid : public Sample
 		e_maxBodyCount = e_maxBaseCount * (e_maxBaseCount + 1) / 2
 	};
 
-	BenchmarkPyramid()
+	BenchmarkPyramid(const Settings& settings)
+		: Sample(settings)
 	{
 		float groundSize = 100.0f;
 		m_groundThickness = 1.0f;
@@ -39,7 +37,8 @@ class BenchmarkPyramid : public Sample
 			m_bodies[i] = b2_nullBodyId;
 		}
 
-		m_baseCount = g_sampleDebug ? 10 : e_maxBaseCount;
+		m_baseCount = g_sampleDebug ? 2 : 80;
+		m_bodyCount = 0;
 
 		CreateScene();
 	}
@@ -59,7 +58,7 @@ class BenchmarkPyramid : public Sample
 		float rad = 0.5f;
 		float shift = rad * 2.0f;
 		float centerx = shift * count / 2.0f;
-		float centery = shift / 2.0f + m_groundThickness + rad * 1.5f;
+		float centery = shift / 2.0f + m_groundThickness;//		+rad * 1.5f;
 
 		b2BodyDef bd = b2DefaultBodyDef();
 		bd.type = b2_dynamicBody;
@@ -77,7 +76,7 @@ class BenchmarkPyramid : public Sample
 
 		for (int32_t i = 0; i < count; ++i)
 		{
-			float y = i * shift + centery;
+			float y = 1.0f + i * shift + centery;
 
 			for (int32_t j = i; j < count; ++j)
 			{
@@ -91,6 +90,8 @@ class BenchmarkPyramid : public Sample
 				index += 1;
 			}
 		}
+
+		m_bodyCount = index;
 	}
 
 	void UpdateUI() override
@@ -99,15 +100,17 @@ class BenchmarkPyramid : public Sample
 		ImGui::SetNextWindowSize(ImVec2(240.0f, 230.0f));
 		ImGui::Begin("Stacks", nullptr, ImGuiWindowFlags_NoResize);
 
-		ImGui::Checkbox("Vel Block Solve", &g_velocityBlockSolve);
-		ImGui::Checkbox("Pos Block Solve", &g_positionBlockSolve);
-
 		bool changed = false;
 		changed = changed || ImGui::SliderInt("Base Count", &m_baseCount, 1, e_maxBaseCount);
 
 		changed = changed || ImGui::SliderFloat("Round", &m_round, 0.0f, 0.4f, "%.1f");
 		changed = changed || ImGui::Button("Reset Scene");
 
+		if (ImGui::Button("Wake Top"))
+		{
+			b2Body_Wake(m_bodies[m_bodyCount - 1]);
+		}
+
 		if (changed)
 		{
 			CreateScene();
@@ -116,12 +119,13 @@ class BenchmarkPyramid : public Sample
 		ImGui::End();
 	}
 
-	static Sample* Create()
+	static Sample* Create(const Settings& settings)
 	{
-		return new BenchmarkPyramid;
+		return new BenchmarkPyramid(settings);
 	}
 
 	b2BodyId m_bodies[e_maxBodyCount];
+	int32_t m_bodyCount;
 	int32_t m_baseCount;
 	float m_round;
 	float m_groundThickness;

samples/collection/benchmark_tumbler.cpp

@@ -9,7 +9,8 @@ class BenchmarkTumbler : public Sample
 {
 public:
 
-	BenchmarkTumbler()
+	BenchmarkTumbler(const Settings& settings)
+		: Sample(settings)
 	{
 		b2BodyId groundId;
 		{
@@ -74,9 +75,9 @@ class BenchmarkTumbler : public Sample
 		}
 	}
 
-	static Sample* Create()
+	static Sample* Create(const Settings& settings)
 	{
-		return new BenchmarkTumbler;
+		return new BenchmarkTumbler(settings);
 	}
 
 	int32_t m_maxCount;

samples/collection/sample_distance.cpp

@@ -13,7 +13,8 @@
 class SampleDistance : public Sample
 {
 public:
-	SampleDistance()
+	SampleDistance(const Settings& settings)
+		: Sample(settings)
 	{
 		m_circle1 = {{0.0f, 0.0f}, 0.5f};
 		m_circle2 = {{0.0f, 0.0f}, 1.0f};
@@ -407,9 +408,9 @@ class SampleDistance : public Sample
 		#endif
 	}
 
-	static Sample* Create()
+	static Sample* Create(const Settings& settings)
 	{
-		return new SampleDistance;
+		return new SampleDistance(settings);
 	}
 
 	b2Polygon m_box;

samples/collection/sample_dynamic_tree.cpp

@@ -26,7 +26,8 @@ static float RayCallback(const b2RayCastInput* input, int32_t proxyId, void* use
 class DynamicTree : public Sample
 {
 public:
-	DynamicTree()
+	DynamicTree(const Settings& settings)
+		: Sample(settings)
 	{
 		m_fill = 1.0f;
 		m_moveFraction = 0.0f;
@@ -248,9 +249,9 @@ class DynamicTree : public Sample
 		m_timeStamp += 1;
 	}
 
-	static Sample* Create()
+	static Sample* Create(const Settings& settings)
 	{
-		return new DynamicTree;
+		return new DynamicTree(settings);
 	}
 
 	b2DynamicTree m_tree;