Physics[2|3]D/PhysWorld[2|3]D: Add max step count

ChangeLog.md

@@ -65,6 +65,7 @@ Nazara Engine:
 - Clock::Restart now returns the elapsed microseconds since construction or last Restart call
 - Add PhysWorld2D::[Get|Set]IterationCount to control how many iterations chipmunk will perform per step.
 - Add PhysWorld2D::UseSpatialHash to use spatial hashing instead of bounding box trees, which may speedup simulation in some cases.
+- Add PhysWorld[2D|3D] max step count per Step call (default: 50), to avoid spirals of death when the physics engine simulation time is over step size.
 
 Nazara Development Kit:
 - Added ImageWidget (#139)

include/Nazara/Physics2D/PhysWorld2D.hpp

@@ -55,6 +55,7 @@ namespace Nz
 			Vector2f GetGravity() const;
 			cpSpace* GetHandle() const;
 			std::size_t GetIterationCount() const;
+			std::size_t GetMaxStepCount() const;
 			float GetStepSize() const;
 
 			bool NearestBodyQuery(const Vector2f& from, float maxDistance, Nz::UInt32 collisionGroup, Nz::UInt32 categoryMask, Nz::UInt32 collisionMask, RigidBody2D** nearestBody = nullptr);
@@ -71,6 +72,7 @@ namespace Nz
 			void SetDamping(float dampingValue);
 			void SetGravity(const Vector2f& gravity);
 			void SetIterationCount(std::size_t iterationCount);
+			void SetMaxStepCount(std::size_t maxStepCount);
 			void SetStepSize(float stepSize);
 
 			void Step(float timestep);
@@ -144,6 +146,7 @@ namespace Nz
 
 			static_assert(std::is_nothrow_move_constructible<PostStepContainer>::value, "PostStepContainer should be noexcept MoveConstructible");
 
+			std::size_t m_maxStepCount;
 			std::unordered_map<cpCollisionHandler*, std::unique_ptr<Callback>> m_callbacks;
 			std::unordered_map<RigidBody2D*, PostStepContainer> m_rigidPostSteps;
 			cpSpace* m_handle;

include/Nazara/Physics3D/PhysWorld3D.hpp

@@ -25,9 +25,11 @@ namespace Nz
 
 			Vector3f GetGravity() const;
 			NewtonWorld* GetHandle() const;
+			std::size_t GetMaxStepCount() const;
 			float GetStepSize() const;
 
 			void SetGravity(const Vector3f& gravity);
+			void SetMaxStepCount(std::size_t maxStepCount);
 			void SetSolverModel(unsigned int model);
 			void SetStepSize(float stepSize);
 
@@ -37,6 +39,7 @@ namespace Nz
 			PhysWorld3D& operator=(PhysWorld3D&&) = delete; ///TODO
 
 		private:
+			std::size_t m_maxStepCount;
 			Vector3f m_gravity;
 			NewtonWorld* m_world;
 			float m_stepSize;

src/Nazara/Physics2D/PhysWorld2D.cpp

@@ -80,6 +80,7 @@ namespace Nz
 	}
 
 	PhysWorld2D::PhysWorld2D() :
+	m_maxStepCount(50),
 	m_stepSize(0.005f),
 	m_timestepAccumulator(0.f)
 	{
@@ -149,6 +150,11 @@ namespace Nz
 		return cpSpaceGetIterations(m_handle);
 	}
 
+	std::size_t PhysWorld2D::GetMaxStepCount() const
+	{
+		return m_maxStepCount;
+	}
+
 	float PhysWorld2D::GetStepSize() const
 	{
 		return m_stepSize;
@@ -291,6 +297,11 @@ namespace Nz
 		cpSpaceSetIterations(m_handle, int(iterationCount));
 	}
 
+	void PhysWorld2D::SetMaxStepCount(std::size_t maxStepCount)
+	{
+		m_maxStepCount = maxStepCount;
+	}
+
 	void PhysWorld2D::SetStepSize(float stepSize)
 	{
 		m_stepSize = stepSize;
@@ -300,7 +311,8 @@ namespace Nz
 	{
 		m_timestepAccumulator += timestep;
 
-		while (m_timestepAccumulator >= m_stepSize)
+		std::size_t stepCount = 0;
+		while (m_timestepAccumulator >= m_stepSize && stepCount < m_maxStepCount)
 		{
 			OnPhysWorld2DPreStep(this);
 
@@ -319,6 +331,7 @@ namespace Nz
 			}
 
 			m_timestepAccumulator -= m_stepSize;
+			stepCount++;
 		}
 	}
 

src/Nazara/Physics3D/PhysWorld3D.cpp

@@ -10,6 +10,7 @@ namespace Nz
 {
 	PhysWorld3D::PhysWorld3D() :
 	m_gravity(Vector3f::Zero()),
+	m_maxStepCount(50),
 	m_stepSize(0.005f),
 	m_timestepAccumulator(0.f)
 	{
@@ -32,6 +33,11 @@ namespace Nz
 		return m_world;
 	}
 
+	std::size_t PhysWorld3D::GetMaxStepCount() const
+	{
+		return m_maxStepCount;
+	}
+
 	float PhysWorld3D::GetStepSize() const
 	{
 		return m_stepSize;
@@ -42,6 +48,11 @@ namespace Nz
 		m_gravity = gravity;
 	}
 
+	void PhysWorld3D::SetMaxStepCount(std::size_t maxStepCount)
+	{
+		m_maxStepCount = maxStepCount;
+	}
+
 	void PhysWorld3D::SetSolverModel(unsigned int model)
 	{
 		NewtonSetSolverModel(m_world, model);
@@ -56,10 +67,12 @@ namespace Nz
 	{
 		m_timestepAccumulator += timestep;
 
-		while (m_timestepAccumulator >= m_stepSize)
+		std::size_t stepCount = 0;
+		while (m_timestepAccumulator >= m_stepSize && stepCount < m_maxStepCount)
 		{
 			NewtonUpdate(m_world, m_stepSize);
 			m_timestepAccumulator -= m_stepSize;
+			stepCount++;
 		}
 	}
 }