b2_distance.h

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// MIT License

// Copyright (c) 2019 Erin Catto

// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:

// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

#ifndef B2_DISTANCE_H
#define B2_DISTANCE_H

#include "b2_api.h"
#include "b2_math.h"

class b2Shape;

struct B2_API b2DistanceProxy
{
        b2DistanceProxy() : m_vertices(nullptr), m_count(0), m_radius(0.0f) {}

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

    void Set(const b2Vec2* vertices, int32 count, float radius);

        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;
        float m_radius;
};

struct B2_API b2SimplexCache
{
        float metric;           
        uint16 count;
        uint8 indexA[3];        
        uint8 indexB[3];        
};

struct B2_API b2DistanceInput
{
        b2DistanceProxy proxyA;
        b2DistanceProxy proxyB;
        b2Transform transformA;
        b2Transform transformB;
        bool useRadii;
};

struct B2_API b2DistanceOutput
{
        b2Vec2 pointA;          
        b2Vec2 pointB;          
        float distance;
        int32 iterations;       
};

B2_API void b2Distance(b2DistanceOutput* output,
                                b2SimplexCache* cache,
                                const b2DistanceInput* input);

struct B2_API b2ShapeCastInput
{
        b2DistanceProxy proxyA;
        b2DistanceProxy proxyB;
        b2Transform transformA;
        b2Transform transformB;
        b2Vec2 translationB;
};

struct B2_API b2ShapeCastOutput
{
        b2Vec2 point;
        b2Vec2 normal;
        float lambda;
        int32 iterations;
};

B2_API bool b2ShapeCast(b2ShapeCastOutput* output, const b2ShapeCastInput* 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;
        float bestValue = b2Dot(m_vertices[0], d);
        for (int32 i = 1; i < m_count; ++i)
        {
                float 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;
        float bestValue = b2Dot(m_vertices[0], d);
        for (int32 i = 1; i < m_count; ++i)
        {
                float value = b2Dot(m_vertices[i], d);
                if (value > bestValue)
                {
                        bestIndex = i;
                        bestValue = value;
                }
        }

        return m_vertices[bestIndex];
}

#endif