70 lines
2.6 KiB
C++
70 lines
2.6 KiB
C++
/*
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* Copyright (c) 2006-2007 Erin Catto http://www.gphysics.com
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*
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* This software is provided 'as-is', without any express or implied
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* warranty. In no event will the authors be held liable for any damages
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* arising from the use of this software.
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* Permission is granted to anyone to use this software for any purpose,
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* including commercial applications, and to alter it and redistribute it
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* freely, subject to the following restrictions:
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* 1. The origin of this software must not be misrepresented; you must not
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* claim that you wrote the original software. If you use this software
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* in a product, an acknowledgment in the product documentation would be
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* appreciated but is not required.
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* 2. Altered source versions must be plainly marked as such, and must not be
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* misrepresented as being the original software.
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* 3. This notice may not be removed or altered from any source distribution.
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*/
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#ifndef B2_TENSORDAMPINGCONTROLLER_H
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#define B2_TENSORDAMPINGCONTROLLER_H
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#include "b2Controller.h"
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class b2TensorDampingControllerDef;
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/// Applies top down linear damping to the controlled bodies
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/// The damping is calculated by multiplying velocity by a matrix in local co-ordinates.
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class b2TensorDampingController : public b2Controller{
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public:
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/// Tensor to use in damping model
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b2Mat22 T;
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/*Some examples (matrixes in format (row1; row2) )
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(-a 0;0 -a) Standard isotropic damping with strength a
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(0 a;-a 0) Electron in fixed field - a force at right angles to velocity with proportional magnitude
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(-a 0;0 -b) Differing x and y damping. Useful e.g. for top-down wheels.
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*/
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//By the way, tensor in this case just means matrix, don't let the terminology get you down.
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/// Set this to a positive number to clamp the maximum amount of damping done.
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float32 maxTimestep;
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// Typically one wants maxTimestep to be 1/(max eigenvalue of T), so that damping will never cause something to reverse direction
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/// @see b2Controller::Step
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void Step(const b2TimeStep& step);
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protected:
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void Destroy(b2BlockAllocator* allocator);
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private:
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friend class b2TensorDampingControllerDef;
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b2TensorDampingController(const b2TensorDampingControllerDef* def);
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};
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/// This class is used to build tensor damping controllers
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class b2TensorDampingControllerDef : public b2ControllerDef
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{
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public:
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/// Tensor to use in damping model
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b2Mat22 T;
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/// Set this to a positive number to clamp the maximum amount of damping done.
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float32 maxTimestep;
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/// Sets damping independantly along the x and y axes
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void SetAxisAligned(float32 xDamping,float32 yDamping);
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private:
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b2TensorDampingController* Create(b2BlockAllocator* allocator) const;
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};
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#endif
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