b2Distance.h

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/*
* Copyright (c) 2006-2009 Erin Catto http://www.box2d.org
*
* This software is provided 'as-is', without any express or implied
* warranty.  In no event will the authors be held liable for any damages
* arising from the use of this software.
* Permission is granted to anyone to use this software for any purpose,
* including commercial applications, and to alter it and redistribute it
* freely, subject to the following restrictions:
* 1. The origin of this software must not be misrepresented; you must not
* claim that you wrote the original software. If you use this software
* in a product, an acknowledgment in the product documentation would be
* appreciated but is not required.
* 2. Altered source versions must be plainly marked as such, and must not be
* misrepresented as being the original software.
* 3. This notice may not be removed or altered from any source distribution.
*/

#ifndef B2_DISTANCE_H
#define B2_DISTANCE_H

#include <Box2D/Common/b2Math.h>

class b2Shape;

struct b2DistanceProxy
{
        b2DistanceProxy() : m_vertices(NULL), m_count(0), m_radius(0.0f) {}

        void Set(const b2Shape* shape, int32 index);

        int32 GetSupport(const b2Vec2& d) const;

        const b2Vec2& GetSupportVertex(const b2Vec2& d) const;

        int32 GetVertexCount() const;

        const b2Vec2& GetVertex(int32 index) const;

        b2Vec2 m_buffer[2];
        const b2Vec2* m_vertices;
        int32 m_count;
        float32 m_radius;
};

struct b2SimplexCache
{
        float32 metric;         
        uint16 count;
        uint8 indexA[3];        
        uint8 indexB[3];        
};

struct b2DistanceInput
{
        b2DistanceProxy proxyA;
        b2DistanceProxy proxyB;
        b2Transform transformA;
        b2Transform transformB;
        bool useRadii;
};

struct b2DistanceOutput
{
        b2Vec2 pointA;          
        b2Vec2 pointB;          
        float32 distance;
        int32 iterations;       
};

void b2Distance(b2DistanceOutput* output,
                                b2SimplexCache* cache, 
                                const b2DistanceInput* input);



inline int32 b2DistanceProxy::GetVertexCount() const
{
        return m_count;
}

inline const b2Vec2& b2DistanceProxy::GetVertex(int32 index) const
{
        b2Assert(0 <= index && index < m_count);
        return m_vertices[index];
}

inline int32 b2DistanceProxy::GetSupport(const b2Vec2& d) const
{
        int32 bestIndex = 0;
        float32 bestValue = b2Dot(m_vertices[0], d);
        for (int32 i = 1; i < m_count; ++i)
        {
                float32 value = b2Dot(m_vertices[i], d);
                if (value > bestValue)
                {
                        bestIndex = i;
                        bestValue = value;
                }
        }

        return bestIndex;
}

inline const b2Vec2& b2DistanceProxy::GetSupportVertex(const b2Vec2& d) const
{
        int32 bestIndex = 0;
        float32 bestValue = b2Dot(m_vertices[0], d);
        for (int32 i = 1; i < m_count; ++i)
        {
                float32 value = b2Dot(m_vertices[i], d);
                if (value > bestValue)
                {
                        bestIndex = i;
                        bestValue = value;
                }
        }

        return m_vertices[bestIndex];
}

#endif